Publications

Sensor and protection technologies against viruses using porphyrin-based MOFs and COFs. Pierre D. Harvey. RSC Applied Interfaces, 2026. https://doi.org/10.1039/D5LF00380F

Abstract: Since the COVID-19 pandemic began in 2020, there has been a surge of interest in detecting, controlling and eradicating viruses, and developing technologies accordingly. The colored, strongly luminescent, and photo- and electrochemically active porphyrin-based metal–organic frameworks (MOFs) and covalent-organic frameworks (COFs) were also explored over the past decade. This review covers significant research developments for efficient viral detection, protection and elimination that occurred mostly during the past decade. Sensor designs utilise porphyrin-based MOFs and COFs as interfaces to selectively detect biological materials associated with target viruses (for example, the capture of RNA as a stimulus) with very high sensitivity, thus allowing for the early diagnosis of their associated diseases. The sensor techniques are based on chemiluminescence, electrochemiluminescence, photoelectrochemical bioassays, and the photodynamic effect. The deactivation of viruses is based on the photodynamic therapy approach, where the photosensitization of singlet oxygen is performed by the porphyrin chromophore, which is unavoidably placed in close proximity to the virus due to the short-lived reactive oxygen species (ROS; 3.1 μs in water). The characteristics of this ROS entity and the underlying mechanism are described with some relevant details. Finally, the development of self-protection is also addressed in the literature, which concerns the modification of face masks with porphyrin-based porous materials for adsorption purposes.

Experimental Validation of Free-Base Porphyrin Derivatives as Antifungal Agents against Botrytis cinerea. Seyed Mehzad Sajjadinezhad, Zachary Goudreau, Frédérik Rivard, Maria Rocio Gonzalez-Lamothe, Benoit Habermayer, Peter Moffett, Kamal Bouarab and Pierre D. Harvey. ACS Agricultural Science & Technology, 2026, 6(1), 92-102. https://doi.org/10.1021/acsagscitech.5c00347

Abstract: Free-base porphyrin derivatives act as photosensitizers to form singlet oxygen, ¹O₂, a reactive oxygen species type II, and as such, they can act as antimicrobial agents. We report on an assessment of several neutral and ionic free-base porphyrin derivatives as potential antifungal agents by testing their effects on the crop pathogen Botrytis cinerea (B. cinerea), both in vitro and in vivo. The free-base ionic porphyrins tested impeded the growth of B. cinerea significantly in the 5–30 ppm concentration range when exposed to light but not under dark conditions. This response is consistent with a mechanism involving the photosensitization of ¹O₂(g), which was confirmed by an observed phosphorescence signal at 1275 nm. Among the free-base porphyrins screened, charged molecules were particularly effective, a property that is associated with their enhanced ability to interact with fungal spores. Interestingly, ionic porphyrins were found to be efficient against various strains of B. cinerea, including those that are resistant to common fungicides, which are routinely used in agriculture. As such, our findings suggest that ionic free-base porphyrin photosensitizers serve as effective and sustainable alternatives to conventional fungicides.

A [Pt]-oligomers polyyne donors for efficient ternary organic Solar Cells. Abdel Aziz Wayzani, Leo Boivin, Quentin Momper, Paul-Ludovic Karsenti, Romuald Herbinet, Christophe Sinturel, Loïc Le Pluart, Pierre D. Harvey, Ganesh D. Sharma and Cyprien Lemouchi. Solar RRL, 2026, e202500663. https://doi.org/10.1002/solr.202500663

Abstract: A ternary organic solar cell (TOSC) P5:PC₇₁BM:Y6 (1:0.2:1) composed of an electron donor 3,4-ethylenedioxythiophene (EDOT)/diketopyrrolopyrrole (DPP)-containing [Pt] (II) polyyne oligomer P5 with the acceptors PC₇₁BM and Y6 shows a significant enhancement of the average power conversion efficiency (PCE) to 16.0% in comparison to the reported binary organic solar cells (OSCs) (P5:PC₇₁BM (1:1.4), PCE = 9.4%; P5:Y6 (1:1.2), PCE = 14.8%). Photophysical investigations carried out on the two binaries and on the ternary highlight the role of PC₇₁BM to increase the rise time of electron transfer and to decrease recombination processes. Investigations of Y6-containing active layers by atomic force microscopy (AFM) and high-resolution transmission electron microscopy (HR-TEM) show the presence of fibers, which highlights the assistance of Y6 in the nanostructuration of the blends. The higher PCE of the TOSC is explained with larger values of short-circuit current density (J_SC) from a broader absorption range and a superior value of fill factor (FF) supported by the faster mobilities and more balanced µ_e/µ_h. This work spotlights the beneficial role of the two acceptors in the TOSC. It explains the achievement of the highest average PCE of 16.0% for [Pt] polyyne oligomers to this date.

Design of a Triple Emissive Cu₄I₄ Coordination Polymer through Ligand Engineering. Léo Boivin, Daniel J. Fortin, and Pierre D. Harvey. Inorganic Chemistry, 64(51), 25311-25322. https://doi.org/10.1021/acs.inorgchem.5c04789

Abstract: Through rational ligand design, the coordination polymer 1D-[Cu₄(μ₃-I)₄(μ₂-L1)₂]_n (CP1; L1 = 1,1-(1′-naphthylthio)methane) has been predictably prepared from CuI and L1 in acetonitrile where both the node, closed cubane Cu₄(μ₃-I)₄ cluster, and the assembling ligand containing naphthyl aromatic pendants are known to be emissive. At liquid nitrogen temperature, CP1 exhibits simultaneously three long-lived emissions centered at 573, 732, and 785 nm, decaying in the ms time scale (∼7.1 ms), which are readily assigned to triplet metal/ligand-to-ligand charge transfer (³ M/XLCT), ligand-centered (³LC; i.e., ³ππ*), and excimer (³excimer), respectively. These assignments, which strikingly diverge from the classical low-energy cluster-centered (³CC) emission emerging from the Cu₄(μ₃-I)₄ cluster, were based on in-depth photophysical studies and advanced quantum simulations by density functional theory (DFT) and time-dependent DFT (TD-DFT), which also calculated the emission maxima with high precision and degree of agreement.

Improving the Singlet Oxygen Photosensitization Activity of Fluorenone-Based Materials. Léo Boivin, Daniel J. Fortin, Paul-Ludovic Karsenti, and Pierre D. Harvey. Inorganic Chemistry, 2025, 64(27), 13715-13728. https://doi.org/10.1021/acs.inorgchem.5c01012

Abstract: The rational design of three coordination polymers based on copper(I) iodide, UDS-7 (1D-Cu₂I₂L7₂)_n, UDS-8 (2D-Cu₂I₂L8₂)_n, and UDS-9 (1D-Cu₂I₂L9₂)_n, using new thioether fluorenones, respectively, 2,7-bis(propylthio)-9-fluorenone (L7), 2,7-bis(4′-methylthiophenyl)-9-fluorenone (L8), and 2,7-bis(methylthio)-9-fluorenone (L9), is reported. The identity of the coordination materials is elucidated by using X-ray diffraction techniques. An in-depth photophysical analysis of L7, L8, L9, UDS-7, UDS-8, and UDS-9 enabled a rational analysis of the properties of the newly synthesized compounds, which are corroborated by density functional theory (DFT) and time-dependent DFT (TD-DFT) computations. The coordination species exhibit ligand centered ^1,3LC emissions, radically contrasting the largely expected metal halide-to-ligand charge-transfer (M/XLCT) behavior. Time-resolved spectroscopic techniques show a relationship between the ligand design and the multiplicity of the ^1,3LC emissive state. Excitation power-dependent photoluminescence analyses indicate the presence of singlet–singlet and triplet–triplet annihilation phenomena in UDS-8 and UDS-9, which is associated with efficient exciton migration within both structures. Near-infrared photoluminescence spectroscopy of the ¹Δ_g → ³∑_g^– emission at 1275 nm provides evidence of singlet oxygen (¹O₂) photosensitization at the solid–gas interface. The photosensitization phenomenon is found to be improved by the incorporation of the L7 and L9 ligands into coordination polymers using CuI (UDS-7 and UDS-9), while L8, due to differing ligand design, remains silent.

Rationalizing the Unexpected Inefficiencies of 3D Porphyrin-MOFs as Singlet Oxygen Photosensitizers Against Botrytis cinerea. Océane Boudreau, Paul Asselin, Seyed Mehrzad Sajjadinezhad, Paul-Ludovic Karsenti, Peter Moffett, Kamal Bouarab, and Pierre D. Harvey. Advanced Materials Interfaces, 2025, 12(14), e00315. https://doi.org/10.1002/admi.202500315

Abstract: Porphyrin-based MOFs (PMOFs) are known to be efficient photocatalysts and singlet oxygen (¹O₂) photosensitizers (PS) in solution, but their application in agriculture and food protection is practically unknown. In vitro tests on Botrytis cinerea using the renowned PCN-222 and PCN-224 reveal modest photo-antifungal activities at the solid–gas interface when compared to their standalone tetrakis(4-carboxyphenyl)porphyrin (TCPP) linker. This in-depth study examines the direct detection of ¹O₂(g) phosphorescence at the solid–air interface, binding of the PMOFs with the spores of B. cinerea by fluorescence microscopy, fluorescence quenching of the PMOFs by oxygen, and rates of exciton migration evaluated through the singlet-singlet annihilation process. The conclusion is that a significant proportion of ¹O₂ is unable to escape the porous materials before deactivation, or does so too late to then be able to reach, and that excitation migration is not efficient enough to generate significant amounts of ¹O₂ directly at the MOF surface. Given that TCPP is its own interface with the gas phase, it is not hindered by these factors, which explains its higher efficiency under these circumstances.

A Porphyrin-Based Metal–Organic Framework as a Photosensitizer for Singlet Oxygen Generation and Photocatalytic Water Treatment. Behrang Salahshournia, Ali Noroozi, Daniel J. Fortin, Lulzim Shketa, Benoit Chabot, Armand Soldera, Hubert Cabana, and Pierre D. Harvey. ACS Applied Optical Materials, 2025, 3(6), 1254-1267. https://doi.org/10.1021/acsaom.5c00068

Abstract: A porphyrin-based metal–organic framework, 3D-[Zn₂(TPyP)(NO₂)₂]_n, (ZnTPyP = 5,10,15,20-tetrapyridylporphyrinzinc(II), node = Zn(NO₂)₂) UDS-2, which exhibits distinct photophysical properties and efficient singlet oxygen photosensitization, has been synthesized and characterized via single-crystal X-ray diffraction. This MOF features an interpenetrated 3D-structure with two different zinc coordination environments, Zn1 (square pyramidal; porphyrin) and Zn2 (quasi-octahedral; Zn(NO₂)₂). Computational analysis reveals an uncommon electronic structure in UDS-2 among porphyrin-based frameworks, where the O atoms of Zn(NO₂)₂ dominate the HOMO contribution leading to a low-energy charge transfer, CT, transition of quasi-nil oscillator strength leading to an optically silent CT state. Conversely, the other frontier MOs are those from the Gouterman model for the porphyrin as expected. UDS-2 demonstrates superior singlet oxygen photosensitization compared to other common porphyrin-based CPs and MOFs such as the 3D-[ZnTPyP]_n framework, PCN-222, and PCN-224. Furthermore, its structural model enables efficient singlet–singlet energy transfer (surface x → core) and exciton migration, which improves singlet oxygen photosensitization. The photocatalytic efficiency of UDS-2 is demonstrated through the degradation of Rhodamine 6G dye and several antibiotics (trimethoprim, ciprofloxacin, ofloxacin, and amoxicillin) in water, where UDS-2 achieves a significant pollutant removal efficiency under visible light at environmentally relevant concentrations (100 ppb). These properties establish UDS-2 as an efficient photosensitizer, generating singlet oxygen in both the solid and aqueous phases.

Simple A-D₂-A Nonfullerene Acceptors for Efficient Binary Bulk Heterojunction Organic Solar Cells. Andrii Byrka, Léo Boivin, Élodie V. d'Astous, Rahul Singhal, Paul-Ludovic Karsenti, Philippe Dauphin-Ducharme, Bernhard Witulski, Ganesh D.Sharma, and Pierre D.Harvey. ACS Applied Materials & Interfaces, 2025, 17(2), 3478-3488. https://doi.org/10.1021/acsami.4c19947

Abstract: Two new nonfused ring nonfullerene electron acceptors, NFAs, (dicarbazolyl)bis(2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile) (MDCzM-4H) and -(2-(5,6-fluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile) (MDCzM-4F), thus exhibiting an A-D₂-A motif, were synthesized and characterized. As thin films, they exhibit the lowest energy absorption signature near 540 nm, extending down to ∼700 nm. This band is due to an intramolecular charge transfer process from the DCz (nonfused dicarbazoyl; DCz) moiety to the malononitrile-based units (M) based on density functional theory calculations (DFT), which are also corroborated by time-dependent DFT (TDDFT) computations. Both NFAs fluoresce in the near-IR region exhibiting a band maximum peaking near 750 nm with biphasic lifetimes in the 75–410 ps time scale. Electrochemical measurements permitted the determination of their HOMO (∼−5.7 eV) and LUMO (∼−4.0 eV) energies. The absorption bands are complementary to those of the commercial copolymer PTB7-Th, which was used to prepare binary blends for photovoltaic cell performance assessments (ITO/PEDOT:PSS/active layer/PFN-Br/Ag). The power conversion efficiencies (PCE) are found to be 10.17% for MDCzM-4H/PTB7-Th (short-circuit current J_SC = 15.87 mA cm^–2; open-circuit voltage V_OC = 1.03 V; fill factor FF = 0.622) and 14.09% for MDCzM-4F/PTB7-Th (J_SC = 20.92 mA cm^–2; V_OC = 0.965 V; FF = 0.698). The use of nonfused ring NFAs achieving such high performances is significant and reveals a path toward simpler NFAs for use in organic photovoltaics.

Thoughts on the Rational Design of MOF-Guest Interactions for Future Intelligent Materials. Paul Asselin and Pierre D. Harvey. Small Methods, 2024, 8(12), 2400584. https://doi.org/10.1002/smtd.202400584

Abstract: The MOF-guest relationship is broken down in elementary phases, descriptors, and parameters. These descriptors and parameters allow precise descriptions of processes, whether they occur at the point when the guest enters the MOF, during the stay, or at the point of exiting. Description of these three phases is possible according to the location of the guest inside the MOF, the activity between MOF and guest, whether stimuli can be used, and whether a selective action can be exercised. The vocabulary provided herein can be useful to better formulate requirements when designing host-guest interactions in, and building new classes of, intelligent materials.

From a simple push–pull dye to a broad-band absorbing and photoconducting material by assembly with CuBr. Léo Boivin, Élodie V. d'Astous, Adrien Schlachter, Daniel J. Fortin, Paul-Ludovic Karsenti, Christophe Lescop, Philippe Dauphin-Ducharme, and Pierre D. Harvey. Journal of Materials Chemistry C, 2024, 12, 16945-16957. https://doi.org/10.1039/D4TC03160A

Abstract: A thermally and electrochemically stable 2D coordination polymer (CP) of formula [Cu₂Br₂L₂]_n (UDS-6) has been designed using the push–pull chromophore ligand 2-(9H-fluorenylidene)malononitrile (L) and the modest and yet non-innocent CuBr salt. Its X-ray structure reveals a series of piled 2D-layers separated by ∼3.55 Å, inside which π-stacked L₂ pairs are placed in a head-to-tail conformation (interplanar L⋯L distance is ∼3.41 Å) and assembled by (CN)₂Cu(μ-Br)2Cu(NC)₂ rhomboids as secondary building units (SBUs) where each nitrile fragment links different L's. UDS-6 exhibits several interesting photonic properties such as a large absorption spectrum extending to ∼1700 nm, a near-infrared (NIR) and anti-Kasha emission (λ_em ∼ 1000 nm), exciton migration across the solid and photoconductivity, all of which drastically differ from those of L in the solid state (absorption extends to ∼600 nm, λ_em ∼ 700 nm, and L is not a photoconductor). Density functional theory (DFT) computations indicate that the lowest energy excited states are metal-halide-to-ligand charge transfer (MXLCT) states where the electron rich Cu₂Br₂ units and the electron withdrawing L act as the electron density donor and acceptor, respectively. UDS-6 is a photoconductor on its own and a mechanism study reveals the presence of photo-induced electron transfer (ET) in a 1 : 1 blend composed of tetraphenylporphyrinzinc(II), ZnTPP, a well-known electron donor, and L within the structure of UDS-6 with a rate, k_ET, of 5.4 × 10⁷ s⁻¹, which assigns L as the electron acceptor and consequently the charge carrier in UDS-6.

CuX-Based MOFs as functional materials for adsorption, catalytic, and sensing applications. Léo Boivin and Pierre D. Harvey. Journal of Materials Chemistry C, 2024, 12, 14253-14282. https://doi.org/10.1039/D4TC03093A

Abstract: Metal–organic frameworks (MOFs) built with nodes of copper(I) halides as metallic nodes have experienced a recent increase in interest as these porous materials exhibit rich physical, photophysical, and chemical properties and applications. In this comprehensive review, these properties and applications are surveyed and described, and include highly luminescent materials exhibiting long-lived excited state lifetimes, high triplet populations, large Stokes shift, etc., which are also of high porosity and rigidity. The auspicious combination of these properties lends them interesting applications such as selective gas adsorption and separation, capture of pollutants, catalysis, and sensing, among others.

Selective Chirality-Driven Photopolymerization of Diacetylene Crystals. Pierre Baillargeon, Léo Boivin, Dorah Vaillancourt, Marilie Bélanger, Tarik Rahem, Daniel Fortin, and Pierre D. Harvey. Crystal Growth and Design, 2024, 24(16), 6829-6837. https://doi.org/10.1021/acs.cgd.4c00844

Abstract: Crystal engineering of two diacetylene monomers was achieved by branching two chiral groups [R = PhC*MeNH(CO₂)CH₂] exhibiting an enantiopure configuration of S,S-(DA2) and an achiral R,S-meso-isomer (DA4). The X-ray structures of DA2 and DA4 reveal the presence of supramolecular arrangements driven by intermolecular H-bonding. A significant intermolecular closer proximity in DA4 than that in DA2 is depicted, ultimately resulting in a slow thermal (days) and swift (min) photochemical polymerization of DA4 to form PDA5, whereas DA2 is unreactive. DFT computations indicate that in both cases the lowest energy-excited state is the charge-transfer state [CT; PhC*MeNH(CO₂) → π*(−C≡C–C≡C−)]. Therefore, this outcome illustrates a drastic selectivity via a settle change in a carbon configuration. Analysis demonstrates that PDA5 is nonemissive and that its coloration arises from a π → π* excitation of the polymer backbone (DFT computations).

Singlet oxygen is an emissive ligand. Paul Asselin, Adrien Schlachter, and Pierre D. Harvey. Chemical Communications, 2024, 60, 8692-8695. https://doi.org/10.1039/D4CC02011A

Abstract: Unprecedented experimental evidence shows that gaseous singlet oxygen (¹O₂) acts as an emissive ligand following collisional photosensitization. This evidence was obtained by monitoring ¹O₂ phosphorescence intensity at ≈1275–1280 nm and the excited state lifetime of singlet oxygen generated by known tetraphenylporphyrin photosensitizers, while varying the atmospheric environment.

The Excited-State N−H Tautomerization Rate in Free-Base Corroles. Adrien Schlachter, Paul-Ludovic Karsenti, Pierre D. Harvey, and Adam Langlois. Chemistry - a European Journal, 2024, 30(48), e202401709. https://doi.org/10.1002/chem.202401709

Abstract: Corrole is a tetrapyrrolic dye with a structure that resembles porphyrin, apart from a single missing carbon. The absence of this carbon results in the re-arrangement of the double bonds within the macrocycle, and the presence of three pyrrolic protons in the central cavity in its free-base form. These protons lead to the existence of two distinct tautomeric structures that exist in a dynamic equilibrium. Although the ground-state energies of the tautomers are similar, the excited states show a significant difference in energy which unbalances the equilibrium between the tautomers and results in rapid excited-state tautomerization, favouring one tautomeric species over the other. Although the excited-state tautomerization process has been known for a long time, very few studies have been performed on it, leaving many key aspects of the process poorly understood. Herein we show how ultrafast photoluminescence can be used to experimentally determine the rates of excited-state tautomerization and activation energies of three free-base corrole derivatives thus allowing us to completely describe the excited-state dynamics of the unusual excited state of free-base corrole and opening the door to the development of new materials that can exploit its unique characteristics.

Best Practices to Directly Assess Heterogeneous Singlet Oxygen Photosensitization by Phosphorescence. Adrien Schlachter, Paul Asselin, Axel Chatelain, and Pierre D. Harvey. Advanced Functional Materials, 2024, 34(41), 2404111. https://doi.org/10.1002/adfm.202404111

Abstract: Literature proves that the direct detection of ¹O₂(¹Δ_g) at the solid gas interface is systematically performed from its phosphorescence using high intensity excitation sources (i.e., lasers), which lead to quasi-ubiquitous chemical problems, such as sensitizer degradation, and photophysical counter-active issues such as ultrafast exciton migration, singlet-singlet and triplet-triplet annihilation, and thermally activated delayed fluorescence mediated by ¹O₂(¹Δ_g). To avoid these inconveniences, low excitation intensity is required but leads to serious analytical challenges. The best practices to reliably detect ¹O₂(¹Δ_g) phosphorescence at various interfaces using a standard excitation source and near-IR detector. The two main practices consist in a gas purging test for reliable identification of ¹O₂(¹Δ_g), and in a particularly fine optimization of the angle made by excitation beam versus substrate plane. These practices are applied to porphyrin sensitizers H₂TPP and ZnTPP, either neat or physiosorbed on glass, quartz, paper and hospital bandages, graphene oxide (GO), and embedded inside electrospun polystyrene fibers and spin coated poly(methyl methacrylate) films. Porphyrin-based metal-organic framework PCN-224, freshly activated, is also examined.

Important Counteranion Effect on Adsorption Efficacity of Hydrogen Sulfide by Silver(I)-Dithione Coordination Polymers. Susan Soleymani-Babadi, Behrang Salahshournia, Azizolla Beheshti, Maryam Bahrani-Pour, Hassan Arefi-Nasab, Peter Mayer, Daniel J. Fortin, Hubert Cabana, and Pierre D. Harvey. ACS Applied Materials & Interfaces, 2024, 16(21), 27875-27886. https://doi.org/10.1021/acsami.4c02350

Abstract: Four new coordination polymers (CPs) have been prepared and evaluated for their efficacy in adsorbing hydrogen sulfide. The reactions of the structurally flexible assembling dithione ligand, L, with different silver(I) salts lead to four new metal–organic coordination architectures (CPs I, III, V, and VIII) exhibiting either one- or two-dimensional networks. CP I, 2D-[(Ag₂Cl₂)L]_n, exhibits a linear series of rhomboid (S)₂Ag(μ₂-Cl)₂Ag(S)₂ secondary building units (SBUs) where S is one of the thione functions of L, altogether forming a 2D-network. CP III, 2D-[(AgI)L]_n, is built upon parallel staircase-shaped 1D-[Ag₂(μ₃-I)₂]_n SBUs bridged by S atoms of L that form a 2D-grid. CP V, 2D-[(AgL)(NO₃)]_n, presents parallel 1D-folded S-shaped [AgL]_n⁺ chains linked by strong argentophilic Ag···Ag interactions, forming a 2D-scaffolding. CP VIII, 1D-[(Ag₂L₃)(Cr₂O₇)]_n, shows 1D-zigzag [{Ag(η²-μ₂,η-μ,μ-L)}₂]_n²ⁿ⁺ chains accompanied by Cr₂O₇^2– counteranions. The adsorption isotherms of H₂S gas by these new CPs were examined and compared to those of related CPs [(Ag₂Br₂)L]_n (II), [(AgCN)₄L]_n (IV), [(Ag₂L)(CF₃SO₃)₂]_n (VI), and [(Ag₂L)(NO₃)(ClO₄)]_n (VII). Among the tested polymers, the 3D-CP IV featuring cyanide anions exhibits the highest adsorption capacity of the CPs studied in this work. In order to determine the reason for this marked difference, density functional theory (DFT) computations were used. All in all, it turns out that the electrostatic interactions (CN^–···H-SH) are significantly stronger than the O^–···H-SH ones. This investigation provides a valuable conceptual tool for other designs of CPs and MOFs having the purpose of capturing toxic gases.

Photophysical properties and photonic applications of porphyrin-based MOFs. Seyed Mehrzad Sajjadinezhad, Léo Boivin, Kamal Bouarab, Pierre D. Harvey. Coordination Chemistry Reviews, 2024, 510, 215794. https://doi.org/10.1016/j.ccr.2024.215794

Abstract: Metal-organic frameworks (MOFs) are a notorious class of porous materials that gained significant attention in recent years due to their unique structural and rich functional properties. Porphyrin-based MOFs, PMOFs, have been studied extensively for their potential applications in areas such as energy storage, capture, delivery, catalysis, and sensing. Particularly, this work first briefly discusses the different types of porphyrin-based MOFs, their electronic structures, and how they interact with light. Furthermore, this article describes the wealth of photophysical events occurring in porphyrin-based MOFs leading to rich properties and sustainable applications upon visible-light irradiation. These include efficient light harvesting, singlet and triplet emissions and aggregation induced emissions, thermally activated delayed fluorescence, nonlinear optical properties, multi-photon absorption, up conversion, singlet-singlet and triplet-triplet excited state annihilation, time-resolved photophysical processes, ultrafast energy and electron transfers, exciton energy migration, photosensitization, photo-conductivity, photo-induced charge separation, optoelectronics, dye sensitized and bulk heterojunction solar cells.

Truxene-to-Fluorenone Energy Transfer in a Robust Mesoporous Zn-MOF. Léo Boivin, Adrien Schlachter, Daniel J. Fortin, and Pierre D. Harvey. Inorganic Chemistry, 2024, 63(1), 141-150. https://doi.org/10.1021/acs.inorgchem.3c02536

Abstract: A new metal–organic framework (MOF; [Zn₄O(hett)_4/3(fluo)_1/2(bdc)_1/2]_n; TFT-MOF) constructed on chromophoric ligands 5,5′,10,10′,15,15′-hexaethyltruxene-2,7,12-triacetate (hett), 9-fluorenone-2,7-dicarboxylate (fluo), terephthalate (bdc), and the Zn₄O node has been prepared and identified by powder X-ray diffraction. This luminescent MOF exhibits large mesoporous pores of 2.7 nm based on computer modeling using density functional theory (DFT) calculations. The steady-state and time-resolved fluorescence spectra and photophysical parameters of TFT-MOF have been investigated and compared with those of the free ligands and their basic chromophores. All in all, TFT-MOF exhibits particularly efficient singlet–singlet energy-transfer processes described as ¹(hett)* → (fluo) and ¹(bdc)* → (fluo), leading to fluorescence arising for the fluo lumophore operating only through Förster resonance energy transfer (FRET) with an efficiency of transfer of up to >95%. This experimental conclusion was corroborated by DFT and time-dependent DFT (TDDFT). For the ¹(hett)* → (fluo) process, the approximated overall rate constant of energy transfer was evaluated to be at most 2.04 × 10¹⁰ s^–1 (using a Stern–Volmer approach of solution data and the relationship between distance and concentration). This process was analyzed using the Förster theory, where two intrapore energy transfer paths of center-to-center distances of 13 and 25 Å have been identified. TFT-MOF photosensitizes the formation of singlet oxygen (¹O₂ (¹Σ_g)) as detected by its phosphorescence signal at 1275 nm.

Statistical Analysis of Copper(I) Iodide and Bis(Diphenylphosphino)alkane-Based Complexes and Coordination Polymers. LéoBoivin, AdrienSchlachter, DanielJ.Fortin, ChristopheLescop, and PierreD.Harvey. Molecules, 2023, 28(23), 7781. https://doi.org/10.3390/molecules28237781

Abstract: The prediction of the metal cluster within a coordination polymer or complex, as well as the dimensionality of the resulting polymer or complex (i.e., 0D, 1D, 2D, or 3D), is often challenging. This is the case for Ph₂P(CH₂)_mPPh₂ ligands (1 ≤ m ≤ 8) and CuX salts, particularly for X = I. This work endeavors a systematic statistical analysis combining studies in the literature and new data, mapping the nature of the resulting CuI aggregates with eight different diphoshphines in 2:1, 3:2, 1:1, 2:3, and 1:2 CuI:Ph₂P(CH₂)_mPPh₂ molar ratios as a function of m, which lead to either pure products or mixtures. Several trends are made relating stoichiometry and chain length to the CuI cluster formed (i.e., globular vs. quasi-planar). Four new X-ray structures were determined: [Cu₃I₂(L1)₃]I, Cu₃I₃(L2)₂, Cu₂I₂(L6)₂, and Cu₄I₄(L8)₂, where m is, respectively, 1, 2, 6, and 8, in which the Cu_xI_y central aggregates adopt triangular bipyramid, diamond, rhomboid, and cubane shaped motifs, respectively. Photophysical measurements assisted the establishment of trends considering the paucity of the crystallographic structures. During this study, it was also found that the 0D-complex Cu₂I₂(Ph₂P(CH₂)₅PPh₂)₂ exhibits thermally activated delayed fluorescence.

Role of 3,4-Ethylenedioxythiophene in the Enhancement of Optical and Charge Transport Properties of Low Band Gap Diketopyrrolopyrrole-Containing Metallooligomers Designed for Organic Solar Cells. Malak Qassab, Jean-François Lohier, Gabriel Marineau-Plante, Abdel Aziz Wayzani, Romuald Herbinet, Muriel Durandetti, Julie Hardouin, Paul-Ludovic Karsenti, Loïc Le Pluart, Pierre D. Harvey, Cyprien Lemouchi, and Ganesh D. Sharma. ACS Applied Energy Materials, 2023, 6(24), 12452-12467. https://doi.org/10.1021/acsaem.3c02337

Abstract: 3,4-Ethylenedioxythiophene (EDOT) diketopyrrolopyrrole (DPP)-containing metallooligomer P5 with platinum complex trans-Pt(PBu₃)₂(C≡C)₂ was synthesized and characterized. The optical and electrochemical properties of P5 are compared to those of previously reported metallooligomers. The insertion of EDOT into the conjugated backbone leads to a decrease in the optical band gap of P5 to 1.48 eV and a broadening of the spectral absorption range (350–840 nm) in agreement with density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations. The structuring effect of EDOT favors a higher planarity of the chain as evidenced on optimized geometry from DFT calculations. Steady state and time-resolved absorption and fluorescence spectroscopy reveal an excellent chemical stability of P5 and permitted to establish a mechanism of formation and relaxation of the electron–hole pair in the P5/PC₇₁BM blend film: (1) The excitation of the polymer (<52.5 ps) P5 + hν → P5*, (2) an ultrafast electron transfer (179 fs), P5* + PC₇₁BM → P5^•+ + PC₇₁BM^•–, and (3) a back electron transfer (1.8 and 25 ps), P5^•+ + PC₇₁BM^•– → ^1,3(P5)* + PC₇₁BM with triplet state relaxation (6.5 ns). The rate constant for electron transfer is 3.5 × 10¹² s^–1. Bulk heterojunction solar cells were fabricated using an active layer prepared from the blend of P5 as the donor with each acceptor PC₇₁BM, IT-4F, or Y6. Good power conversion efficiencies (PCE) are reached with PC₇₁BM (PCE = 9.46%), but they are higher with IT-4F (PCE = 11.02%) and reach a maximum value with Y6 (PCE = 14.81%). This work highlights the beneficial role of EDOT on the enhancement of solar cell properties with the increase of charge mobilities and external quantum efficiency. The highest value of PCE obtained with P5:Y6 (15.03%) is a record-high PCE for any [Pt]-containing polyyne oligomers.

Strong Host–Guest Dependence on the Emissive Properties of MOF-5 and [Zn₂(BTTB)(DMF)₂•(H₂O)₃]_n. Adrien Schlachter, Paul Asselin, Daniel J. Fortin, Paul-Ludovic Karsenti, and Pierre D. Harvey. Inorganic Chemistry, 2023, 62(34), 13757-13764. https://doi.org/10.1021/acs.inorgchem.3c01378

Abstract: 3D-[Zn₄O(1,4-BDC)₃•x(solvent)]_n (MOF-5; BDC = 1,4-benzodicarboxylate) and 3D-[Zn₂(BTTB)(DMF)₂•(H₂O)₃]_n (MOF-D; BTTB = 4,4′,4″,4‴-benzene-1,2,4,5-tetrayltetrabenzoate) have been investigated by means of steady-state UV–visible and fluorescence and time-resolved emission spectroscopy, as a function of solvent and power of the excitation irradiation. The low-temperature X-ray structures (173 K) were permitted to locate solvent molecules (here H₂O) in the lattice. They were found distributed in the middle in the voids with no evidence of specific interactions (H-bond, coulombic, and dipole–dipole) with the framework. The fluorescence decays of the ligands (ππ* excited state), τ_F, for the host–guest composites MOF-5@solvent and MOF-D@solvent (solvent = air, MeCN, EtCN, MeOH, EtOH, and DMF) were found bi-exponential (short τ_F1 (ps), and long τ_F2 (ns)) with one important feature: upon cooling from 298 to 77 K, MOF-5’s τ_F1 decreases and τ_F2 increases, while the opposite trend is generally observed in MOF-D. The low values for τ_F1 (ps) in MOF-5 are associated with the augmented probability of solvent-ligand collisions leading to nonradiative deactivation, which upon cooling to 77 K increases further as the scaffolding contracts. The augmentation in τ_F2 is readily associated with the increased rigidity of the ligands that are not submitted to this effect (at the surface of the MOF and as pendent groups). For the low emitter MOF-D, the reversed situation is noted but not as clearly due to the uncertainties in the data. Upon increasing the excitation flux, the fluorescence intensity increases linearly with the laser power indicating the absence of singlet–singlet annihilation, inferring the absence of efficient exciton migration. This observation is explained by the small absorptivity coefficients, which leads to a small J spectral overlap between absorption and fluorescence according to the Forster and Dexter theories, and consequently, a small rate for energy migration. This conclusion drastically changes the perception of the photocatalytic mechanism of MOF-5 and other MOFs exhibiting similar absorption features (i.e., no antenna effect).

Removal of heavy and toxic metals from wastewater using porphyrin-based covalent-organic frameworks: An emerging Field. Pierre D. Harvey. Journal of Porphyrins and Phthalocyanines, 2023, 27 (07-10), 1015-1027. https://doi.org/10.1142/S1088424623300112

Abstract: This mini-review assembles the current advances in the adsorption of heavy elements and toxic metals, namely Cr(VI), Mn(II), Ni(II), Cu(II), Tc(VII), Cd(II), Re(VII), Pt(IV), Au(III), Hg(II), Pb(II), and U(VI), bromate (BrO−3), and iodine (I2) in water, as well as the visible-light-driven heterogeneous photocatalytic reduction of highly harmful metal ions into less hazardous or soluble metallic cations, mainly U(VI) + light → U(IV) and Au(III) + light → Au NPs, by the porous and highly colored porphyrin-based covalent-organic frameworks (COFs) in water.

Sustainable development in the removal and photocatalytic reduction of heavy metals in wastewaters using environmentally friendly and health benign Porphyrin-based Metal-Organic frameworks. Pierre D. Harvey. Separation and Purification Technology, 2023, 322, 124214. https://doi.org/10.1016/j.seppur.2023.124214

Abstract: Porphyrin is a rigid, electron-rich, and highly colored chromophore and with anchoring groups, such as carboxylates, can be an important unit of the scaffolding building porous materials called metal–organic frameworks, MOFs. The metallic nodes are generally polymetallic oxides, and together with porphyrins, form semiconducting materials. The porosity, absorption of visible light, material tailoring to modulate the particle dimension, relative ease for post-functionalization, and facile metalation of the corresponding free base, make these MOFs for multitude applications, notably removal of heavy metals from wastewaters. This review assembles the current advances in the removal of heavy elements and toxic metals, namely Cr(III), Cr(VI), Mn(II), Fe(VI), Co(II), Cu(II), Zn(II), Mo(VI), Pd(II), Ag(I), Cd(II), Sb(III), Pt(IV), Au(III), Hg(II), Pb(II), Bi(III), Rb(I), Sr(II), Cs(I), U(VI) and iodine, as well as the visible light driven heterogeneous photocatalytic reduction of highly harmful metal ions into less hazardous or less soluble metallic cations or nanoparticles (Cr(VI) → Cr(III), U(VI) → U(IV), Pd(II) → Pd(0)) by the porous, highly colored porphyrin-based MOFs in water. The pH-dependent capture of the metal ions are generally driven by five main strategies; 1) ionic interactions or H-bonds with the MOF skeleton, 2) coordination of metal cations by the porphyrin macrocycle free base, 3) post-functionalization of a chelating arm inside the MOFs, 4) photochemical process rendering the metal ion less toxic, and 5) photochemical rendering the metal ion less soluble, thus remaining trapped. This work covers other relevant topics such as structures of the porphyrin-based MOFs, photoinduced electron transfer and formation of reactive oxygen species of types I, comparison of the adsorption capacities with other MOFs, assessment of the no or negligible toxicity of these MOFs, discussion on the scale-up, activation of MOFs and the notable neglected toxic metal ions. This detailed and critical review is the most complete survey on what these multifunctional MOFs can do in this area.

Rather Simple D–A Nonfullerene for High-Performance Indoor Photovoltaic Cells. Adrien Schlachter, Gabriel Marineau-Plante, Daniel J. Fortin, Ganesh D. Sharma, and Pierre D. Harvey. ACS Applied Energy Materials, 2023, 6(9), 4961-4970. https://doi.org/10.1021/acsaem.3c00437

Abstract: A simple push–pull nonfullerene, N-(2-ethylhexyl)-3-carbazolyl-2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile, MCz, has been prepared and fully characterized, including absorption, fluorescence, excitation, time-resolved fluorescence, density functional theory (DFT) and time-dependent-DFT, cyclic voltammetry, and single-crystal crystallography. The organic solar cells were also fabricated in a bulk heterojunction (BHJ) with the conventional architecture ITO/PEDOT:PSS/active layer/PFN/Al and were characterized in both outdoor (AM1.5 G) and indoor light sources. The active layer consists of the polymer donor PTB7-Th blended with MCz, which was compared to another related blend, PTB7-Th:MCzM (MCzM = N-(2-ethylhexyl)-3,6-carbazolyl-bis[2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile]). The outdoor data were extracted at AM 1.5. The short-circuit current (J_sc), open-circuit voltage (V_oc), fill factor (FF), and power conversion efficiency (PCE) are as follows for MCzM: 16.67 mA/cm², 1.02 V, 0.66, and 10.55%, respectively, and for MCz: 17.26 mA/cm², 0.84 V, 0.606, and 8.79%, respectively. The indoor photovoltaic data are as follows for MCzM: 81.08 μA/cm², 0.88 V, 0.66, and 18.88%, respectively, and for MCz: 111.95 μA/cm², 0.74 V, 0.68, and 22.14%, respectively.

Virus Management Using Metal–Organic Framework-Based Technologies. Léo Boivin and Pierre D. Harvey. ACS Applied Materials and Interfaces, 2023, 15(11), 13844-13859. https://doi.org/10.1021/acsami.3c00922

Abstract: The eradication and isolation of viruses are two concurrent approaches to protect ourselves from viral infections and diseases. The quite versatile porous materials called metal–organic frameworks (MOFs), have recently emerged as efficient nanosized tools to manage viruses, and several strategies to accomplish these tasks have been developed. This review describes these strategies employing nanoscale MOFs against SARS-CoV-2, HIV-1, tobacco mosaic virus, etc., which include the sequestration by host–guest penetration inside pores, mineralization, design of a physical barrier, controlled delivery of organic and inorganic antiviral drugs or bioinhibitors, photosensitization of singlet oxygen, and direct contact with inherently cytotoxic MOFs.

Assessment of photosensitization performance and stability of host-guest MCM-41 composites from the direct observation of singlet oxygen formation and properties. Tatevik Chilingaryan, Adrien Schlachter, Céline Frochot, Benoit Habermeyer, Pierre D. Harvey, and Roger Guilard. Journal of Porphyrins and Phthalocyanines, 2023, 27(01-04), 517-525. https://doi.org/10.1142/S108842462350030X

Abstract: New heterogeneous porous materials based on 5,10,15,20-(tetraphenyl)porphyrin (H₂TPP), 5,10,15,20-(tetra-N-methyl-4-pyridyl)porphyrin tetrachloride (H₂TNMPyP), zinc(II) 5,10,15,20-(tetra-N-methyl-4-pyridyl)porphyrin tetrachloride (ZnTNMP_yP), 5,10,15,20-(tetra-4-carboxyphenyl)porphyrin (H₂TCPP) and zinc(II)5,10,15,20-(tetra-4-carboxyphenyl)porphyrin (ZnTCPP) have been incorporated into mesoporous silica MCM-41 from slow diffusion of solutions containing different concentrations of porphyrin chromophores. Successful incorporation of all porphyrins has been confirmed by UV-Vis spectroscopy and TGA. XRD patterns of these silica-based host-guest samples prove that the mesoporous structure of MCM-41 remains unchanged after encapsulation. The potential abilities of these photosensitizers to form singlet oxygen (¹O2) at the solid state/air interface after light excitation were investigated. Despite the variable amount of encapsulated porphyrin derivatives (based on UV-vis assessment and chemical analysis), the phosphorescence intensity of ¹O₂ peak at 1270 nm remains relatively the same from one composite to the other meaning that the photosensitizers are mainly placed at the surface of the MCM-41 particles.

Metal-porphyrinic framework nanotechnologies in modern agricultural management. Seyed Mehrzad Sajjadinezhad, Kevin Tanner, and Pierre D. Harvey. Journal of Materials Chemistry B, 2022, 10, 9054-9080. https://doi.org/10.1039/D2TB01516A

Abstract: Metal-porphyrinic frameworks are an important subclass of metal–organic frameworks (MOFs). These porous materials exhibit a large number of applications for sustainable development and related environmental considerations. Their attractive features include (1) as a free base or metalated with zinc(II) or iron(II or III), they are environmentally benign, and (2) they absorb visible light and are emissive and semi-conducting, making them convenient tools for sensing agrochemicals. But the key feature that makes these nano-sized pristine materials or their composites in many ways superior to most MOFs is their ability to photo-generate reactive oxygen species with visible light, including singlet oxygen. This review describes important issues related to agriculture, including controlled delivery of pesticides and agrochemicals, detection of pesticides and pathogenic metals, elimination of pesticides and toxic metals, and photodynamic antimicrobial activity, and has an important implication for food safety. This comprehensive review presents the progress of the rather rapid developments of these functional and increasingly nano-sized materials and composites in the area of sustainable agriculture.

S-Heptazine N-ligand based luminescent coordination materials: synthesis, structural and luminescent studies of lanthanide–cyamelurate networks. Mohamed Essalhi, Midhun Mohan, Gabriel Marineau-Plante, Adrien Schlachter, Thierry Maris, Pierre D. Harvey, and Adam Duong. Dalton Transactions, 2022, 51, 15005-15006. https://doi.org/10.1039/D2DT01924H

Abstract: Various series of lanthanide metal–organic networks denoted Ln–Cy (Ln = La, Ce, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb), were synthesized under solvothermal conditions using potassium cyamelurate (K₃Cy) and lanthanide nitrate salts. All obtained materials were fully characterized, and their crystal structures were solved by single-crystal X-ray diffraction. Four types of coordination modes were elucidated for the Ln–Cy series with different Ln³⁺ coordination geometries. Structural studies were performed to compare the various coordination compounds of the Ln–Cy series. Moreover, the cyamelurate linkers of rich π-conjugated and uncoordinated Lewis basic sites were used as an absorbing chromophore to enhance the luminescence quantum efficiency, the band emission and the luminescence lifetime of the coordinated Ln metal centers. Solid-state UV-visible measurements combined with density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations were performed to further explore luminescent features of the Ln–Cy series and their origins.

Structural Influence on Exciton Migration and Singlet Oxygen Photosensitization in Porphyrinic Metal–Organic Coordination Networks. Paul Asselin, Adrien Schlachter, Daniel J. Fortin, Paul-Ludovic Karsenti, and Pierre D. Harvey. Chemistry of Materials, 2022, 34(16), 7242-7255. https://doi.org/10.1021/acs.chemmater.2c01105

Abstract: A hexagonal three-dimensional (3D) metal–organic coordination network (MOCN) [(ZnTPyP)·0.75 DMSO]_n (3D Helix) and a one-dimensional (1D) coordination polymer [(ZnTPyP)·DMF]_n (1D Ladder) (ZnTPyP = 5,10,15,20-tetrakis(4-pyridyl)porphyrinatozinc(II)) are prepared and their photophysical properties are investigated to assess their ability to promote efficient exciton energy migration through singlet–singlet annihilation processes and to photosensitize singlet oxygen (¹O_2(g)). The presence and absence of annihilation in 3D Helix and 1D Ladder, respectively, are indicative of their ability to efficiently promote exciton migration. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were used to demonstrate the presence of interporphyrin couplings in the 3D Helix structure. Using Forster’s theory of energy transfer, the relative efficiencies of exciton migration across the bulk were correlated with the structural parameter κ²/r⁶, indicative of the relative orientations and distance between the donor and acceptor. Concurrently, based on the magnitude of ¹O_2(g) phosphorescence (1280 nm), it was noted that 3D Helix photosensitizes ¹O_2(g) more efficiently than 1D Ladder (by roughly 1 order of magnitude). During this study, a new two-dimensional (2D)-MOCN was prepared, 2D Grid [(ZnTPyP)·4CHCl₃]_n, but weak Zn···N interactions and evaporation of CHCl₃ transformed 2D Grid into a multiphasic mixture (ZnTPyP Morph) containing both 3D Helix and other 1D ladder-like species.

Chain Length Effect on the Structural and Emission Properties of the CuI/Bis((4-methoxyphenyl)thio)alkane Coordination Polymers. Adrien Schlachter, Rebecca Scheel, Daniel J. Fortin, Carste Strohmann, Michael Knorr, and Pierre D. Harvey. Inorganic Chemistry, 2022, 61(29), 11306-11318. https://doi.org/10.1021/acs.inorgchem.2c01427

Abstract: A systematic chain length variation of the ligand para-MeOC₆H₄S(CH₂)_mSC₆H₄OMe (1 ≤ m ≤ 8) was performed to study its effect on the structures and photophysical properties of the coordination polymers (CP) when reacted with CuI. Indeed, direct correlations are noted between these features and m. When m is an odd number, the secondary building unit is systematically the common closed-cubane Cu₄I₄ cluster, rendering the material strongly luminescent (i.e., emission quantum yield, Φ_e > 20%), and the CP is one-dimensional (1D). However, when m is 2, 4, and 6, the SBUs exhibit rare polymeric motifs of (Cu₂I₂)_n: staircase ribbon, fused poly(rhombic pseudo-dodecahedron), and accordion ribbon, respectively, and the emission intensities are either very weak (Φ_e < 0.001%) or of medium intensity (Φ_e ∼ 10% when m = 6). When m = 8 (i.e. the most flexible chain), the SBU is a closed-cubane Cu₄I₄ and the emission intensity is medium (Φ_e ∼ 10%). A special case was observed for m = 3, where a co-crystallization of the molecular cluster Cu₄I₄(NCCH₃)₄ is observed in the lattice, which turns out to be quite important for the stability of the network.

Visible-Light-Driven Production of Solar Fuels Catalyzed by Nanosized Porphyrin-Based Metal–Organic Frameworks and Covalent–Organic Frameworks: A Review. Paul Asselin, and Pierre D. Harvey. ACS Applied Nano Materials, 2022, 5(5) 6055-6082. https://doi.org/10.1021/acsanm.2c00831

Abstract: Porphyrin-based materials are excellent chromophores because they strongly absorb visible light and their relatively low-energy lowest unoccupied molecular orbitals thermodynamically favor photoinduced electron transfer. They can generate charge-transfer excited states with and without cocatalyst(s) and ease energy transfer and ultrafast excitation energy migration. Combined with synthetic accessibility, these qualities make them ideal building blocks for porous metal–organic framework (MOF)- and covalent–organic framework (COF)-based photocatalysts to produce solar fuels. This review first describes the structures of the most common porphyrinic MOFs and COFs and their excited-state properties and semiconducting behavior as well as that of derived composites. The generally accepted mechanisms of formation of H₂, CH₄ and derivatives, and N₂ are then reviewed, followed by the detailed examples of nano-MOFs and nano-COFs used for the said purpose: characteristic parameters such as rates of production, turnover numbers (TONs), turnover frequencies (TOFs), and apparent quantum efficiencies are described and compared. This shows that porphyrin-based MOFs and COFs are efficient solar-fuel-producing photocatalysts, with characteristics comparable to those of nonporphyrinic MOF and COF photocatalysts, although, on some occasions, the rates of production fall short of record values. Conversely, porphyrinic MOFs and COFs exhibit the greatest TONs and TOFs of any solar-fuel-producing MOFs or COFs but still face shortcomings concerning selectivity in CH₄ production because of the many possible side products. Importantly, while the best rate of photoproduction of solar fuels has been observed from nanoscale photocatalysts, there seem to be no drastic differences in the rate (within μmol^–1 h^–1 and mmol g^–1 h^–1) between nanoscale and microscale heterogeneous photocatalysts. This observation suggests that the more active sites are mostly located at or near the surface of the particles. Overall, nanosized porphyrin-based MOFs and COFs show rich and promising photocatalytic properties for generating solar fuels but still have room for improvement.

Efficient ternary bulk heterojunction organic solar cells using a low-cost nonfullerene acceptor. Adrien Schlachter, Gabriel Marineau-Plante, Pierre D. Harvey, Anupam Agrawal, and Ganesh D. Sharma. Journal of Materials Chemistry C, 2022, 10, 4372-4382. https://doi.org/10.1039/D1TC05653K

Abstract: In order to improve the power conversion efficiency of single junction polymer solar cells (PSCs), we have used a ternary blend consisting of a low bandgap D–A conjugated polymer P and two acceptors, i.e., one nonfullerene, Cz-IC, and one fullerene, PC₇₁BM. The concept of a ternary bulk heterojunction (BHJ) using these two acceptors takes advantage of the high electron mobility of the fullerene, which is beneficial for charge transport. The absorption spectra of PC₇₁BM, Cz-IC and P are complementary to each other, resulting in an increase in the light harvesting ability of the ternary BHJ active layer. The PSC based on an optimized ternary BHJ active layer achieved a PCE of 15.27%, which is higher than those of both binary PSCs based on P:PC₇₁BM and P:Cz-IC. The increase in J_SC and FF values for the ternary PSC with respect to the P:Cz-IC binary counterpart may be attributed to the better and balanced charge transport properties owing to the high electron mobility of PC₇₁BM. The incorporation of PC₇₁BM into the P:Cz-IC blend also increases the hole transfer efficiency from both acceptors to P, thus reducing the charge recombination, resulting in a boost of the fill factor and the overall PCE of the ternary OSC.

Photoreductive Electron Transfers in Nanoarchitectonics Organization Between a Diketopyrrolopyroleplatinum(II)-Containing Organometallic Polymer and Various Electron Acceptors. Gabriel Marineau-Plante, Malak Qassab, Adrien Schlachter, Mélodie Nos, Muriel Durandetti, Julie Hardouin, Cyprien Lemouchi, Loïc Le Pluart, and Pierre D. Harvey. Journal of Inorganic and Organometallic Polymers and Materials, 2022, 32, 1266-1276. https://doi.org/10.1007/s10904-021-02170-3

Abstract: A platinum(II) polyyne/diketopyrrolopyrole-containing polymer of two different chain lengths, P (short) and P’ (long chain), were prepared in order to elucidate the reasons for the poor photoconversion efficiencies (PCEs) in bulk heterojunction solar cells recently reported in the Journal of Organometallic Chemistry (2019), 894, 1–9, whereas other solar cells using similar platinum(II) polyyne/diketopyrrolopyrole-containing polymers provided significantly better PCEs. Using thermodynamic arguments using electrochemical and spectroscopy data, quenching experiments of the fluorescence band of P using fullerene (PC₆₁BM and PC₇₁BM) nonfullerene (MCzM) acceptors, and testing photochemical stability of P and P’, three possible reasons were found. These reasons are the undetected photochemical instability of similar polymers used by Wong, and the likely inappropriate choice of electron acceptor (PC₆₁BM) in this past investigation.

Significant differences between solid state and solution photochemistry and photophysics of mesogenic organometallic gold complexes. Kevin Tanner, Gabriel Marineau-Plante, Adrien Schlachter, Paul-Ludovic Karsenti, Armand Soldera, and Pierre D. Harvey. Canadian Journal of Chemistry, 2022, 100(2), 150-161. https://doi.org/10.1139/cjc-2021-0120

Abstract: Five new gold complexes 4-ROC₆H₄C≡CAuN≡CC₆H₄-4-OR′ (R/R′ = CH₃/C₉H₁₉ (C₁N₉), C₁₅H₃₁/C₉H₁₉ (C₁₅N₉), C₆H₁₃/C₁₅H₃₁ (C₆N₁₅), C₉H₁₉/C₁₅H₃₁ (C₉N₁₅), C₁₂H₂₅/C₁₅H₃₁ (C₁₂N₁₅)) were synthesized and characterized (¹H and ¹³C NMR, IR, Raman spectroscopy, and high resolution mass spectrometry). Their organized smectic phases were investigated by TGA, DSC, powder XRD, and polarized light optical microscopy, and the solids are found to have crystalline and amorphous domains. No evidence for Au•••Au interactions was observed. The steady state and time-resolved absorption and emission properties at 298 and 77 K were examined, and surprisingly, the excited lifetime of the triplet excited state in the solid state is extremely short-lived (<100 ps) in comparison with the microsecond time scale recorded for the solution and at 77 K. The photosensitization of ¹O₂ was observed in solution but not in the solid state. The nature of the singlet (ligand-to-ligand charge transfer) and triplet (ethynyl/intraligand ππ*) excited states were assessed using DFT and TD-DFT computations. The thermal and UV-photochemical formation of gold nanoparticles were performed in solution (slow) and in the solid state (faster). The thermally generated nanoparticles are found to be larger (2–20 nm; TEM) and exhibit well-defined shapes, whereas the photochemically generated ones are smaller (1–10 nm) and show ill-defined shapes.

Porphyrin-based metal- and covalent-organic frameworks as heterogeneous nanosized photocatalysts in organic synthesis. Pierre D. Harvey. Journal of Materials Chemistry C, 2021, 9, 16885-16910. https://doi.org/10.1039/D1TC04147A

Abstract: The porphyrin-containing metal- and covalent-organic frameworks, respectively MOFs and COFs, are quite versatile porous nanomaterials for hetero-photocatalysis. Indeed, they are capable of catalysing the photoinduced reduction of CO₂ and metal, contaminant degradation, H₂ and O₂ evolutions, photodynamic therapy, and thermotherapy, and biomimicry. Concurrently, they are also efficient photocatalysts for a large variety of organic reactions. This mini-review presents a comprehensive account of the current state of the art in this area and includes several examples of CO₂ transformation for the preparation of plus value chemicals such as methane and cyclic carbonates, formation of peroxides including Juglone, ascaridole and Artemisinin, ketones from benzyl alcohols and N-methylquinolinium salts, and imines from the photooxidative coupling of benzylamines and 2-aminobenzamides, selective oxidation of sulfides into sulfoxides, hydroxylation of aromatic boronic acids, various cases of C–C formations from diazo compounds and stable C–H bonds and oxidative Mannich reactions, C–P bond formations from aerobic cross dehydrogenative-coupling reactions with amines, and C–X bond activations (X = H, F, Br), reduction of nitroaromatics, dehydrogenation of tetrahydroquinolines, deprotection of aromatic ketones from their corresponding aryloxathiolanes, and asymmetric Strecker reactions. It also includes pertinent details regarding the generation of reactive oxygen species (ROS) of types I and II occurring during photoinduced electron and energy transfer processes within the porous heterogeneous nanocatalysts, which play a major role in the transformation of organic molecules.

Copper halide-chalcogenoether and -chalcogenone networks: Chain and cluster motifs, polymer dimensionality and photophysical properties. Adrien Schlachter, Kevin Tanner, and Pierre D. Harvey. Coordination Chemistry Reviews, 2021, 448, 214176. https://doi.org/10.1016/j.ccr.2021.214176

Abstract: Copper(I) halides react with mono- and polychalcogenoethers and -chalcogenones to form 0-3D coordination materials containing neutral polynuclear Cu_xX_xE_y species (E = S, Se, Te; X  = Cl, Br, I; x  = 2–8) called secondary building units (SBU). These species exhibit two general types of motifs namely globular and quasi-planar. Depending on the shape of these polynuclear species and the dimensionality of the network, their properties and applications are profoundly different. In a structural point of view for instance, when X = I, and E = S, the globular family includes cubane, open cubane, fused dicubane, fused open dicubane, hexagonal prism, and 1D-polycubane. Concurrently, the quasi-planar family includes rhomboid, trinuclear cluster, step staircase, 1D-zig zag ribbon, 1D-acordeon ribbon and 1D-staircase ribbon. Both the cubane and rhomboid motifs are overwhelmingly represented (>80%). Generally, the globular species are generally strongly luminescent. In contrast, the quasi-planar family exhibits only modest intensity luminescence or no emission at all. This review provides a thorough statistical analysis of these SBUs, in a structural point of view, along with their photophysical properties.

A Fused Poly(truncated rhombic dodecahedron)-Containing 3D Coordination Polymer: A Multifunctional Material with Exceptional Properties. Adrien Schlachter, Kevin Tanner, Rebecca Scheel, Paul-Ludovic Karsenti, Carsten Strohmann, Michael Korr, and Pierre D. Harvey. Inorganic Chemistry, 2021, 60(17), 13528-13538. https://doi.org/10.1021/acs.inorgchem.1c01856

Abstract: The design of new and inexpensive metal-containing functional materials is of great interest. Herein is reported a unique thermochromic near-IR emitting coordination polymer, 3D-[Cu₈I₈(L1)₂]_n, CP2, which is formed when ArS(CH₂)₄SAr (L1, Ar = 4-C₆H₄OMe) reacts with 2 equiv of CuI in EtCN. In MeCN, CP1 ([Cu₄I₄(L1)(MeCN)₂]_n, consisting of an alternating [-Cu₄I₄-L1-Cu₄I₄-L1-]_n chain where the Cu₄I₄ cubane units bear two metal-bound MeCN molecules, is formed. Heat-driven elimination of these MeCN’s in solid CP1 also leads to CP2 through a predisposed organization of the Cu₄I₄ units prone to fusion after MeCN eliminations (i.e., a rare case of template effect). The CP2 structure exhibits parallel 1D-(Cu₈I₈)_n chains, (z-axis; designated 1D-[CuI]_n) as secondary building units (SBU) held together by parallel thioether ligands (x,y-axes), forming a nonporous 3D network. The structure of this 1D-[CuI]_n SBU is unprecedented and consists of a series of fused and twisted open Cu₄I₄ cubanes forming a fused poly(truncated rhombic dodecahedron). Unexpectedly, the compact 3D CP2 exhibits a solid-to-solid phase transition at 100 °C and a hysteresis of ∼20 °C. CP1 emits intensively (298 K: λ_emi = 564 nm; Φ_e = 0.35), whereas CP2 presents a strongly red-shifted weaker emission (298 K: λ_emi ∼ 740 nm, Φ_e < 0.0001). Moreover, CP2, which is stable over long periods of time, exhibits thermochromism where the emission intensity of the near-IR band decreases significantly at the benefit of a ligand-centered phosphorescence at 415 nm. Altogether, these properties listed above make CP2 exceptional. The low-energy singlet and triplet excited states have been assigned to ligand/metal-to-ligand charge transfer based on DFT and TD-DFT computations.

New phosphorescent iridium(iii) dipyrrinato complexes: synthesis, emission properties and their deep red to near-infrared OLEDs. Hongyang Zhang, Haitao Wang, Kevin Tanner, Adrien Schlachter, Zhao Che, Pierre D. Harvey, Shuming Chen, and Wai-Yeung Wong. Datlon Transactions, 2021, 50, 10629-10639. https://doi.org/10.1039/D1DT01557E

Abstract: A series of heteroleptic Ir(III) complexes composed of two cyclometalated C^N ligands and one dipyrrinato ligand used as an ancillary ligand are synthesized and characterized. With the introduction of a fluorine atom, phenyl ring or diphenylamino group into both C^N ligands and by keeping the ancillary ligand unchanged, these Ir(III) dipyrrinato phosphors do not show an obvious shift in their emission bands. They exhibit emissions extending well into the near-infrared region with an intense band located at around 685 nm in both photo- and electroluminescence spectra, and the deep red to near-infrared organic light emitting diodes (OLEDs) based on them afforded a maximum external quantum efficiency of 2.8%. Density functional theory (DFT) calculations show that both the electronic contributions on the lowest unoccupied molecular orbitals (LUMOs) and the highest energy semi-occupied molecular orbitals (HSOMOs) are mainly localized on the dipyrrinato ligand, indicating that the ancillary ligand, which remains unchanged in this series, exhibits a lower triplet state energy in the iridium phosphors than those involving the C^N ligands. Therefore a switch from “(C^N)₂Ir” to dipyrrinato ligand-based emission is observed in these iridium(III) complexes.

Porphyrin-Containing MOFs and COFs as Heterogeneous Photosensitizers for Singlet Oxygen-Based Antimicrobial Nanodevices. Adrien Schlachter, Paul Asselin, and Pierre D. Harvey. ACS Applied Materials and Interfaces, 2021, 13(23), 26651-26672. https://doi.org/10.1021/acsami.1c05234

Abstract: Visible-light irradiation of porphyrin and metalloporphyrin dyes in the presence of molecular oxygen can result in the photocatalytic generation of singlet oxygen (¹O₂). This type II reactive oxygen species (ROS) finds many applications where the dye, also called the photosensitizer, is dissolved (i.e., homogeneous phase) along with the substrate to be oxidized. In contrast, metal–organic frameworks (MOFs) are insoluble (or will disassemble) when placed in a solvent. When stable as a suspension, MOFs adsorb a large amount of O₂ and photocatalytically generate ¹O₂ in a heterogeneous process efficiently. Considering the immense surface area and great capacity for gas adsorption of MOFs, they seem ideal candidates for this application. Very recently, covalent–organic frameworks (COFs), variants where reticulation relies on covalent rather than coordination bonds, have emerged as efficient photosensitizers. This comprehensive mini review describes recent developments in the use of porphyrin-based or porphyrin-containing MOFs and COFs, including nanosized versions, as heterogeneous photosensitizers of singlet oxygen toward antimicrobial applications.

Properties and applications of copper halide-chalcogenoether and -chalcogenone networks and functional materials. Adrien Schlachter and Pierre D. Harvey. Journal of Materials Chemistry C, 2021, 9, 6648-6685. https://doi.org/10.1039/D1TC00585E

Abstract: When copper(I) halide salts react with various mono- and poly-chalcogenoether and -chalcogenone ligands, two general shapes of neutral polynuclear Cu_xX_xE_y species (E = S, Se, Te; X = Cl, Br, I; x = 2–8) are formed within the resulting 0–3D coordination materials. These polymetallic forms exhibit either globular or quasi-planar motifs, mainly closed cubane Cu₄I₄S₄ and rhomboid Cu₂X₂S₄, respectively, but not exclusively. Depending on the shape of these polynuclear species and the dimensionality of the network, their properties and applications are profoundly different. These materials include luminescent and electroactive materials, sensors for small molecules, thermo-, electro- and photocatalysts, therapeutic and antibacterial species, electrically conducting solids, active components in solar cells and light emitting diodes, and functional and stimuli-responsive materials (such as self-healing). Specific properties such as occurrence of solid-to-solid phase transition and thermo- and mechano-chromism have also been observed. This work summarizes these properties and applications and presents their current research directions.

Porphyrin-based MOFs as heterogeneous photocatalysts for the eradication of organic pollutants and toxins. Pierre D. Harvey. Journal of Porphyrins and Phthalocyanines, 2021, 25(07-08), 583-604. https://doi.org/10.1142/S1088424621300020

Abstract: Water and air pollution are among the major environmental challenges of this era. Waste management, economic sustainable development and renewable energy are unavoidable concomitant considerations. Over the past five years, nanosized metal-organic frameworks (nano-MOFs) have been developed for the elimination of pollutants in wet media and air-born toxins using the highly efficient reactive oxygen species (ROS) of type I (H₂O₂, •OH, O∙−2) and of type II (¹O2). The ROS are catalytically and efficiently generated through photosensitization, and porphyrins and metalloporphyrins are pigments of choice for this purpose. This short review summarizes the fundamentals of ROS generation by porphyrin-based nano-MOFs (mainly through the formation of ROS type II) and their composites (leading to ROS type I), which includes energy and electron transfer processes, and their applications in these environmental issues.

Recent Advances in Nanoscale Metal–Organic Frameworks Towards Cancer Cell Cytotoxicity: An Overview. Pierre D. Harvey and Jessica Plé. Journal of Inorganic and Organometallic Polymers and Materials, 2021, 31, 2715-2756. https://doi.org/10.1007/s10904-021-02011-3

Abstract: The fight against cancer has always been a prevalent research topic. Nanomaterials have the ability to directly penetrate cancer cells and potentially achieve minimally invasive, precise and efficient tumor annihilation. As such, nanoscale metal organic frameworks (nMOFs) are becoming increasingly attractive as potential therapeutic agents in the medical field due to their high structural variability, good biocompatibility, ease of surface functionalization as well as their porous morphologies with tunable cavity sizes. This overview addresses five different common strategies used to find cancer therapies, while summarizing the recent progress in using nMOFs as cytotoxic cancer cell agents largely through in vitro studies, although some in vivo investigations have also been reported. Chemo and targeted therapies rely on drug encapsulation and delivery inside the cell, whereas photothermal and photodynamic therapies depend on photosensitizers. Concurrently, immunotherapy actively induces the body to destroy the tumor by activating an immune response. By choosing the appropriate metal center, ligands and surface functionalization, nMOFs can be utilized in all five types of therapies. In the last section, the future prospects and challenges of nMOFs with respect to the various therapies will be presented and discussed.

Indolo- and Diindolocarbazoles in Organic Photovoltaic Cells. Pierre D. Harvey, Ganesh D. Sharma, and Bernhard Witulski. Chemistry Letters, 2021, 50(7), 1345-1355. https://doi.org/10.1246/cl.210050

Abstract: Over the past decades, indolo- and diindolocarbazoles have been incorporated in bulk heterojunction solar cells (BHJSCs) as electron donors - either as small molecules or within the backbone of conjugated push-pull polymers. Recently, these units were used as nonfullerene electron acceptors, resulting in superior photoconversion efficiencies (PCEs). Their motif consists of D-A or A-D-A units (D = electron-donor; A = electron-acceptor). This review focuses on the reasons why that is so.

The TDDFT Excitation Energies of the BODIPYs; The DFT and TDDFT Challenge Continues. Adrien Schlachter, Alexandre Fleury, Kevin Tanner, Armand Soldera, Benoit Habermeyer, Roger Guilard, and Pierre D. Harvey. Molecules, 2021, 26(6), 1780. https://doi.org/10.3390/molecules26061780

Abstract: The derivatives of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) are pivotal ingredients for a large number of functional, stimuli-responsive materials and therapeutic molecules based on their photophysical properties, and there is a urgent need to understand and predict their optical traits prior to investing a large amount of resources in preparing them. Density functional theory (DFT) and time-dependent DFT (TDDFT) computations were performed to calculate the excitation energies of the lowest-energy singlet excited state of a large series of common BODIPY derivatives employing various functional aiming at the best possible combination providing the least deviations from the experimental values. Using the common “fudge” correction, a series of combinations was investigated, and a methodology is proposed offering equal or better performances than what is reported in the literature.

2-Azabutadiene complexes of rhenium(i): S,N-chelated species with photophysical properties heavily governed by the ligand hidden traits. Adrien Schlachter, Frank Juvenal, Rodolphe Kinghat Tangou, Abderrahim Khatyr, Fabrice Guyon, Paul-Ludovic Karsenti, Carsten Strohmann, Marek M. Kubicki, Yoann Rousselin, Pierre D. Harvey, and Michael Knorr. Dalton Transactions, 2021, 50, 2945-2963. https://doi.org/10.1039/D0DT04183A

Abstract: The reaction of [Re(CO)₃(THF)(μ-Br)]₂ or [Re(CO)₅X] (X = Cl, Br, I) with the diaryl-2-azabutadienes [(RS)₂CC(H)–NCAr₂] containing two thioether arms at the 4,4-position forms the luminescent S,N-chelate complexes fac-[(OC)₃ReX{(RS)₂CC(H)–NCAr₂}] (1a–h). The halide abstraction by silver triflate converts [(OC)₃ReCl{(PhS)₂CC(H)–NCPh₂}] (1c) to [(OC)₃Re(OS(O)₂CF₃){(PhS)₂CC(H)–NCPh₂}] (1j) bearing a covalently bound triflate ligand. The cyclic voltammograms reveal reversible S^N ligand-centred reduction and irreversible oxidation waves for all complexes. The crystal structures of nine octahedral complexes have been determined along with that of (NaphtylS)₂CC(H)–NCPh₂ (L6). A rich system of weak non-covalent intermolecular secondary interactions through CH⋯X(Cl, Br)Re, CH⋯O, CO⋯π(Ph), CH⋯πCO, CH⋯O and CH⋯S contacts has been evidenced. The photophysical properties have been investigated by steady-state and time-resolved absorption (fs transient absorption, fs-TAS) and emission (ns-TCSPC and ps-Streak camera) spectroscopy in 2-MeTHF solution at 298 and 77 K. The emission bands are composed of either singlet (450 < λ_max < 535 nm) and/or triplet emissions (at 77 K only, λ_max < 640 nm, or appearing as a tail at λ > 600 nm), which decay in a multiexponential manner for the fluorescence (short ps (i.e. <IRF) < τ_F < 1.9 ns at 298 and 77 K) and monoexponentially for the phosphorescence (4.0 < τ_P < 7.0 ns at 77 K). The fs-TAS data reveal the presence of 2 to 4 transient species decaying in four narrow time windows (generally 125–165 fs, 370–685 fs, 3–6 ps, 30–45 ps). The complexity of these kinetics was explained by studying the photophysical behaviour of ligand L6. Its behaviour is the same as the complexes thus indicating that the ligand dictates the kinetic traits of the Re-species, except for the triplet emission as L6 is not phosphorescent. The triplet lifetime (4.0 < τ_P < 7.0 ns) is considered very short but not unprecedented. Furthermore, the nature of the lowest energy excited states of these chelate compounds and L6 has been addressed using DFT and TDDFT calculations and been assigned to metal-to-ligand (MLCT) and/or intraligand charge-transfer (ILCT).

Effect of Mesogenic Side Groups on the Redox, Photophysical, and Solar Cell Properties of Diketopyrrolopyrrole-trans-bis(diphosphine)diethynylplatinum(II) Polymers. Gabrie Marineau-Plante, Mélodie Nos, Di Gao, Muriel Durandetti, Julie Hardouin, Paul-Ludovic Karsenti, Cyprien Lemouchi, Loïc Le Pluart, Ganesh D. Sharma, and Pierre D. Harvey. ACS Applied Polymer Materials, 2021, 3(2), 1087-1096. https://doi.org/10.1021/acsapm.0c01325

Abstract: Three ([Pt]-DPP)_n polymers PA, PB, and PC bearing cyanobiphenyl, alkyloxyphenyl, and triphenylene self-assembling groups were synthesized. The optical, electrochemical, photophysical, and solar cell properties were investigated and compared to analogue polymer P1 deprived of any organizing group. Significant differences lie in the more stabilized lowest unoccupied molecular orbital (LUMO) level for PA and the highest occupied molecular orbital (HOMO) level for PC. X-ray diffraction analyses on thin films evidenced π-aggregation of molecules for PA and PB. Nanosecond timescale fluorescent lifetimes were measured for PA, PB, and PC. An ultrafast photoinduced electron transfer between these polymers and phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) was brought out from femtosecond transient absorption spectroscopy (fs-TAS). It is faster for PC than for PA and PB. The recombination leads to singlet- and triplet-state formation (([Pt]-DPP)_n)^•+ + PC₆₁BM^•– → ³([Pt]-DPP)_n* + ([Pt]-DPP)_n + PC₆₁BM. Solar cells were fabricated using polymers blended with an acceptor (PC₇₁BM or IT-4F) as an active layer in conventional device structure indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/active layer/poly[(9,9-dioctyl-2,7-fluorene)-alt-(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)] (PFN)/Al. Unlike PA, polymers PB and PC exhibit better photovoltaic performances than P1. Higher power conversion efficiencies (PCEs) were reached with IT-4F, PB:IT-4F (PCE = 10.83%, J_sc = 17.83 mA cm^–2, V_oc = 0.98 V), and PC:IT-4F (PCE = 13.26%, J_sc = 18.95 mA cm^–2, V_oc = 1.06 V). This work highlights the beneficial impact of triphenylene self-assembling groups on photovoltaic properties. PC exhibits a record-high PCE (13.26%) for [Pt]-containing polyyne oligomers and small molecules.

Ultrafast Energy Transfer from Local Exciton to Intermolecular CT States in a Supramolecular Model of the Donor–Acceptor Interfaces. Loïc Tanguy, Alexandre Fleury, Paul-Ludovic Karsenti, Gessie Brisard, Armand Soldera, and Pierre D. Harvey. The Journal of Physical Chemistry C, 2020, 124(30), 16248-16260. https://doi.org/10.1021/acs.jpcc.0c02381

Abstract: The donor–acceptor contacts in bulk heterojunctions (BHJ) is the birthplace of primary energy leaks in organic solar cells (OSCs): V_oc (voltage at open circuit) losses. These interfaces are the least understood and the least accessible experimentally. A bottom up approach is being used to mimic this interface via supramolecular interactions of two graphene-based materials: reduced graphene oxide, RGO, and, graphene nanoribbon, GNR, with six different pyrene-linked dyes used as probes to assess the photophysical changes observed upon interface formation in a donor–acceptor bulk heterojunction device. These assemblies are secured through strong π–π interactions between pyrene anchors and GNR, and the formation of these probe–GNR assemblies were studied by absorption spectroscopy. A total of 11 static charge transfer (CT) complexes were identified in 6 different donor–acceptor interfaces, and their properties and dynamics were studied by steady state, time-resolved fluorescence and transient absorption spectroscopy. Three distinct cases were identified: (1) nonharvesting CT assemblies, (2) harvesting and emissive CT assemblies, and (3) harvesting but nonemissive CT complexes. The excitons of the GNR chains are rapidly and fully channeled to the CT complex (<1 ps). Depending on the driving force, the formation of long-lived CT states (302–483 ps) is observed. A three-state model with a coupling between a CT state and a local exciton (LE) is used to describe the behavior of this interface. A HOMO_GNR–HOMO_2PyrPBI energy gap of 0.16 eV is found to be large enough to efficiently promote a pure charge transfer state at the interface.

Design of P-Chirogenic Aminophosphine–Phosphinite Ligands at Both Phosphorus Centers: Origin of Enantioselectivities in Pd-Catalyzed Allylic Reactions. Antonin Jaillet, Christophe Darcel, Jérôme Bayardon, Adrien Schlachter, Christine Salomon, Yoann Rousselin, Pierre D. Harvey, and Sylvain Jugé. The Journal of Organic Chemistry, 2020, 85(22), 14391-14410. https://doi.org/10.1021/acs.joc.0c00536

Abstract: We have recently patented an unprecedented stereospecific N → O phosphinyl migration process which transforms P-chirogenic aminophosphines into phosphinites. A fine design of aminophosphine phosphinite ligands (AMPP*) derived from ephedrine and bearing a P-chirogenic center either at the aminophosphine or phosphinite moiety was performed. The synthesis of AMPP* ligands with a P-chirogenic aminophosphine moiety was based on the well-established stereospecific reaction of oxazaphospholidine borane with organolithium reagents, followed by trapping with a chlorophosphine and borane decomplexation. Concurrently, the preparation of AMPP* ligands with a P-chirogenic phosphinite moiety was performed by N → O phosphinyl migration of aminophosphines borane by heating at 50 °C with DABCO and then reaction with chlorophosphines. AMPP* ligands were studied in palladium-catalyzed asymmetric allylic alkylations, leading to enantioselectivities from 91% (R) to 95% ee (S). X-ray crystallographic data for relevant Pd–AMPP* complexes and computer modeling explained the origin of the enantioselectivities based on MO interactions of most stable conformers with nucleophiles.

A Platinum(II) Organometallic Building Block for the Design of Emissive Copper(I) and Silver(I) Coordination Polymers. Frank Juvenal, Daniel J. Fortin, and Pierre D. Harvey. Inorganic Chemistry, 2020, 59(10), 7117-7134. https://doi.org/10.1021/acs.inorgchem.0c00584

Abstract: The tritopic organometallic ligand trans-MeSC₆H₄C≡CPt(PMe₃)₂(C≡N) (L1) was prepared from cis-PtCl₂(PMe₃)₂ and p-ethynyl(methyl thioether)benzene. Its versatility was shown with the formation of [CuX(L1)]_n coordination polymers (CPs) with CuX salts in MeCN (X = I (CP1), CN (CP2), SCN (CP3)). These CPs were characterized by X-ray crystallography, thermal gravimetric analysis (TGA), and IR and Raman spectroscopy. CP1 consists of a 1D head-to-tail chain formed by tricoordinated −C≡N–CuI(η²-C≡C)– linkages, whereas CP2 is built upon a central (CuCN)_n zigzag chain bearing dangling L1s held by −C≡N–Cu bonds. Finally, CP3 exhibits 2D sheets secured by Cu–N≡C–/–(Me)S–Cu bondings and transversal Cu–S–C≡N–Cu bridges. Concurrently, the CPs formed with AgX (X = NO₃^– (CP4 and CP5), CF₃CO₂^– (CP6) PF₆^– (CP7)) exhibits 2D sheets with guest molecules (anion, solvents) inside the tight pores or between layers. These new materials are emissive: L1 (λ_0–0 ∼465 nm), CP1–CP7 (500 < λ_max < 620 nm). Their photophysical properties (absorption and emission spectra, emission lifetimes (∼0.2 < τ_e < 120 μs), and quantum yields in the solid state at 77 and 298 K) were analyzed. The various natures of the emissive excited states were addressed by density functional theory (DFT) and time-dependent DFT (TDDFT) computations. For CP1, this state is a triplet halide or pseudohalide to ligand charge transfer ³XLCT (CT = charge transfer; X = I; L = L1) and for CP2, it is ³XLCT (X = CN; L = L1). However, for CP3, it is ³XLCT (X = SCN; L = L1). For CP4, the T₁ state is described as a [MeSC₆H₄(η²-C≡C)-Ag(NO₃)]₂ → [Pt]/C≡CC₆H₄SMe CT.

From Short-Bite Ligand Assembled Ribbons to Nanosized Networks in Cu(I) Coordination Polymers Built Upon Bis(benzylthio)alkanes (BzS(CH₂)_nSBz; n = 1–9). Adrien Schlachter, Antony Lapprand, Daniel J. Fortin, Carsten Strohmann, Pierre D. Harvey, and Michael Knorr. Inorganic Chemistry, 2020, 59(6), 3686-3708. https://doi.org/10.1021/acs.inorgchem.9b03275

Abstract: With the objective to establish a correlation between the spacer distance and halide dependence on the structural features of coordination polymers (CPs) assembled by the reaction between CuX salts (X = Cl, Br, I) and dithioether ligands BzS(CH₂)_nSBz (n = 1–9; Bz = benzyl), a series of 26 compounds have been prepared and structurally investigated. A particular attention has been devoted to the design of networks with extremely long and flexible methylene spacer units between the SBz donor sites. Under identical conditions, CuI and CuBr react with BzSCH₂Bz (L1) affording respectively the one-dimensional (1D) CPs {Cu(μ₂-I)₂Cu}(μ-L1)₂]_n (CP1) and {Cu(μ₂-Br)₂Cu}(μ-L1)₂] (CP2), which incorporate Cu(μ₂-X)₂Cu rhomboids as secondary building units (SBUs). The hitherto unknown architecture of two-dimensional (2D) layers obtained with CuCl (CP3) differs from that of CP1 and CP2, which bear inorganic −Cl–Cu–Cl–Cu–Cl– chains interconnected through bridging L1 ligands, thus forming a 2D architecture. The crystallographic characterization of a 1D CP obtained by reacting CuI with 1,3-bis(benzylthio)propane (L2) reveals that [{Cu(μ₂-I)₂Cu}(μ-L2)₂]_n (CP4) contains conventional Cu₂I₂ rhomboids as SBUs. In contrast, unusual isostructural CPs [{Cu(μ₂-X)}(μ₂-L2)]_n (CP5) and (CP6) are obtained with CuX when X = Br and Cl, respectively, in which the isolated Cu atoms are bridged by a single μ₂-Br or μ₂-Cl ion giving rise to infinite [Cu(μ₂-X)Cu]_n ribbons. The crystal structure of the strongly luminescent three-dimensional (3D) polymer [{Cu₄(μ₃-I)₃(μ₄-I)(μ-L3)_1.5]_n (CP7) issued from reacting 2 equiv of CuI with BzS(CH₂)₄SBz (L3) has been redetermined. CP7 features unusual [(Cu₄I₃)(μ₄-I)]_n arrays securing the 3D connectivity. In contrast, mixing CuI with an excess of L3 provides the nonemissive material [{Cu(μ₂-I)₂Cu}(μ-L3)₂]_n (CP8). Treatment of CuBr and CuCl with L3 leads to [{Cu(μ₂-Br)₂Cu}(μ-L3)₂]_n (CP9) and the 0D complex [{Cu(μ₂-Cl)₂Cu}(μ-L3)₂] (D1), respectively. The crystallographic particularity for CP9 is the coexistence of two topological isomers within the unit cell. The first one, CP9-1D, consists of simple 1D ribbons running along the a axis of the unit cell. The second topological isomer, CP9-2D, also consists of [Cu(μ₂-Br)₂Cu] SBUs, but these are interconnected in a 2D manner forming 2D sheets placed perpendicular to the 1D ribbons. Four 2D CPs, namely, [{Cu₄(μ₃-I)₄}(μ-L4)₂]_n (CP10), [{Cu(μ₂-I)₂Cu}(μ-L4)₂]_n (CP11), [{Cu(μ₂-Br)₂Cu}(μ-L4)₂]_n (CP12), and [{Cu(μ₂-Cl)₂Cu}(μ-L4)₂]_n (CP13), stem from the self-assembly process of CuX with BzS(CH₂)₆SBz (L4). A similar series of 2D materials comprising [{Cu₄(μ₃-I)₄}(μ-L5)₂]_n (CP14), [{Cu(μ₂-I)₂Cu}(μ-L5)₂]_n (CP15), [{Cu(μ₂-Br)₂Cu}(μ-L5)₂]_n (CP16), and [{Cu(μ₂-Cl)₂Cu}(μ-L5)₂]_n (CP17) result from the coordination of BzS(CH₂)₇SBz (L5) on CuX. Ligation of CuX with the long-chain ligand BzS(CH₂)₈SBz (L6) allows for the X-ray characterization of the luminescent 2D [{Cu₄(μ₃-I)₄}(μ-L6)₂]_n (CP18) and the isostructural 1D series [{Cu(μ₂-X)₂Cu}(μ-L6)₂]_nCP19 (X = I), CP20 (X = Br) and CP21(X = Cl). Noteworthy, BzS(CH₂)₉SBz (L7) bearing a very flexible nine-atom chain generated the crystalline materials 2D [{Cu₄(μ₃-I)₄}(μ-L7)₂]_n (CP22) and the isostructural 1D series [{Cu(μ₂-X)₂Cu}(μ-L6)₂]_nCP23 (X = I), CP24 (X = Br), and CP25 (X = Cl), featuring nanometric separations between the cubane- or rhomboid-SBUs. This comparative study reveals that the outcome of the reaction of CuX with the shorter ligands BzS(CH₂)_nSBz (n = 1–4) is not predictable. However, with more flexible spacer chains BzS(CH₂)_nSBz (n = 6–9), a clear structural pattern can be established. Using a 1:1 CuX-to-ligand ratio, [{Cu(μ₂-X)₂Cu}(μ-L4–7)₂] CPs are always formed, irrespectively of L4–L7. Employing a 2:1 CuX-to-ligand ratio, only CuI is able to form networks incorporating Cu₄(μ₃-I)₄ clusters as SBUs. All attempts to construct polynuclear cluster using CuBr and CuCl failed. The materials have been furthermore analyzed by powder X-ray diffraction, Raman spectroscopy, and thermogravimetric analysis, and the photophysical properties of the emissive materials have been studied.

A bis(diketopyrrolopyrrole) dimer-containing ligand in platinum(ii) polyyne oligomers exhibiting ultrafast photoinduced electron transfer with PCBM and solar cell properties. Mélodie Nos, Gabriel Marineau-Plante, Di Gao, Muriel Durandetti, Julie Hardouin, Paul-Ludovic Karsenti, Gaurav Gupta, Ganesh D. Sharma, Pierre D. Harvey, Cyprin Lemouchi, and Loïc Le Pluart. Journal of Materials Chemistry C, 2020, 8, 2363-2380. https://doi.org/10.1039/C9TC03487K

Abstract: Two polyyne oligomers using the thiophene–(diketopyrrolopyrrole)–thiophene unit, T–DPP–T, and the organometallic synthon trans-Pt(PBu₃)₂(CC)₂, [Pt], ([L1]–[Pt])_m (P1), here used for comparison purposes, and ([L4]–[Pt])_m (P4), where L1 and L4 are T–DPP–T and (T–DPP–T)₂, respectively, were synthesized by CuI-catalyzed dehydrohalogenation and fully characterized. The optical and electrochemical properties were investigated by UV-visible absorption and cyclic voltammetry, and P4 was found to exhibit a very low band gap. DFT (density functional theory) and TD-DFT (time-dependent DFT) computations were undertaken to address the polymers’ geometry, their electronic structures and calculated HOMO and LUMO energies. The S₁ level is best described as a ππ* excited state. P1 and P4 exhibit fluorescence lifetime in ps timescale and the fs-TAS data indicate an ultrafast electron transfer to PC₆₁BM ((¹Px* + PC₆₁BM → Px⁺˙ + (PC₆₁BM)⁻˙; time scale < 113–128 fs) evidenced by an increased formation of the triplet state upon back electron transfer (Px⁺˙ + (PC₆₁BM)⁻˙) → ^1,3Px* + PC₆₁BM; x = 1, 4). The timescale of recombination for P4 (P4⁺˙ + (PC₆₁BM)⁻˙ → ³P4* + PCBM) is found to be ∼3 ps. The photovoltaic performance of Px was investigated by fabricating the photovoltaic solar cells (PSCs) with conventional device structure ITO/PEDOT:PSS/(P1 or P4):PC₇₁BM/PFN/Al. After solvent vapour annealing with THF, the power conversion efficiencies, PCEs, are 7.36% (P1; J_sc = 12.94 mA cm⁻², V_oc = 0.92 V, FF = 0.62) and 9.54% (P4; J_sc = 16.24 mA cm⁻², V_oc = 0.89 V, FF = 0.66). The higher PCE of P4 may be related to the faster extraction and longer charge carrier lifetime for P4 based PSCs as compared to P1.

Reactivity of the (trans-Pt(PMe₃)₂(C≡CC₆H₄SMe)₂) Ligand with Copper Cyanide: Formation of the [Cu₂(μ₂-C≡CC₆H₄SMe)₂]_n Polymer. Frank Juvenal, and Pierre D. Harvey. Journal of Inorganic and Organometallic Polymers and Materials, 2020, 30, 159-168. https://doi.org/10.1007/s10904-019-01298-7

Abstract: The organometallic ligand trans-Pt(PMe₃)₂(C≡CC₆H₄SMe)₂, L1, reacts with C≡N⁻ ions (as sodium salt) in various stoichiometric ratios to form L3, [trans-Pt(PMe₃)₂(C≡N)₂], and MeSC₆H₄C≡C⁻ anions, which were identified using various spectroscopic techniques (¹H and ³¹P NMR, and ESI-TOF). Concurrently, the capture of the released MeSC₆H₄C≡C⁻ units by Cu(I) metals was observed when L1 was reacted with CuCN in excess. In this case, two new coordination polymers (CPs), [Cu(μ₂-C≡CC₆H₄SMe)]_n (CP1) and [CuCN(L2)]_n (CP2) where L2 is the new ligand [trans-Pt(PMe₃)₂(C≡CC₆H₄SMe)(C≡N)] formed along with the [trans-Pt(PMe₃)₂(C≡N)₂] complex in small amount. CP1 was also synthesized independently to secure its identification. CP1 was found to be emissive at both 298 and 77 K. The nature of its emissive excited state was found to be an intraligand MeSC₆H₄C≡C⁻³ππ* mixed with some atomic contributions of the copper(I) d-orbitals based on DFT computations.

A 9.16% Power Conversion Efficiency Organic Solar Cell with a Porphyrin Conjugated Polymer Using a Nonfullerene Acceptor. Loïc Tanguy, Prateek Malhotra, Surya Prakash Sing, Gessie Brisard, Ganesh D. Sharma, and Pierre D. Harvey. ACS Applied Materials & Interfaces, 2019, 11(13), 28078-28087. https://doi.org/10.1021/acsami.9b05463

Abstract: A new low-molecular-weight porphyrin-based polymer, PPPyDPP, with pyridine-capped diketopyrrolopyrrole (DPP) has been synthesized, and its optical and electrochemical properties were investigated. The polymer is prepared with a low content of homocoupling units and gives a widely spread absorption from 400 to 900 nm with a narrow optical band gap of 1.46 eV. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels are respectively located at −5.27 and −3.78 eV, respectively. PPPyDPP was used as the electron donor, whereas [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM) and bis(rhodanine)indolo-[3,2-b]-carbazole (ICzRd₂), a nonfullerene small molecule, were used as acceptors for the fabrication of solution-processed bulk heterojunction polymer solar cells. Overall power conversion efficiencies (PCEs) of 7.31 and 9.16% (record high for porphyrin-containing polymers) were obtained for PC₇₁BM and ICzRd₂, respectively. A high V_oc of 1.01 V and a low E_loss of 0.45 eV may explain this new record.

Unusual triplet–triplet annihilation in a 3D copper(i) chloride coordination polymer. Adrien Schlachter, Antoine Bonnot, Daniel J. Fortin, Paul-Ludovic Karsenti, Michael Knorr, and Pierre D. Harvey. Physical Chemistry Chemical Physics, 2019, 21, 16538-16548. https://doi.org/10.1039/C9CP02891A

Abstract: A new coordination polymer (CP) defined as [Cu₂Cl₂(EtS(CH₂)₄SEt)₄]_n (CP2) was prepared by reacting EtS(CH₂)₄SEt with CuCl in acetonitrile in a 1 : 2 stoichiometric ratio. The X-ray structure reveals formation of non-porous 3D material composed of parallel 2D-[Cu₂Cl₂S₂]_n layers of Cl-bridged Cu₂(μ-Cl)₂ rhomboids assembled by EtS(CH₂)₄SEt ligands. A weak triplet emission (Φ_e < 0.0001) is observed in the 400–500 nm range with τ_e of 0.93 (298 K) and 3.5 ns (77 K) as major components. CP2 is the only 2nd example of emissive thioether/CuCl-containing material and combined DFT/TDDFT computations suggest the presence of lowest energy M/XLCT excited states. Upon increasing the photon flux (i.e. laser power), a triplet–triplet annihilation (TTA) is induced with quenching time constants of 72 ps (k_Q = 1.3 × 10¹⁰ s⁻¹) and 1.0 ns (k_Q = 7.1 × 10⁸ s⁻¹) at 298 and 77 K, respectively, proceeding through an excitation energy migration operating via a Dexter process. Two distinct (I_o)^1/2 (I_o = laser power) dependences of the emission intensity are depicted, indicating saturation as the observed emission increases with the excitation flux. These findings differ from that previously reported isomorphous CP [Cu₂Br₂(μ-EtS(CH₂)₄SEt)₄]_n (CP1), which exhibits no TTA behaviour at 77 K, and only one (laser power)² dependence at 298 K. The ∼18-fold increase in k_Q upon warming CP2 from 77 to 298 K indicates a temperature-aided TTA process. The significant difference between the presence (slower, CP2) and absence (CP1) of TTA at 77 K is explained by the larger unit cell contraction of the former upon cooling. This is noticeable by the larger change in inter-rhomboid Cu⋯Cu separation for CP2.

Drastic effect of the substituent on the anthraquinone diimine moiety on the properties of the push-pull trans-bisphosphinebisphenylacetynylplatinum(II)-containing polymers. Frank Juvenal, Hu Lei, Paul-Ludovic Karsenti, and Pierre D. Harvey. Journal of Organometallic Chemistry, 2019, 896, 24-31. https://doi.org/10.1016/j.jorganchem.2019.05.024

Abstract: A new emissive polymer ([Pt]-(AQI(OR)₂))_n, P2, where AQI is anthraquinone diimine, [Pt] is trans-bis(ethynylbenzene)bis(tributylphosphine)platinum(II) and R is n-butyl, has been prepared in order to compare with the related polymer ([Pt]-(AQI(NO₂)₂))_nP1 (Macromolecular Chemistry and Physics (2018), 219(22), 1800354). In addition to the difference in substituent effect (electron donor, O-n-Bu; electron acceptor, NO₂), the first notable difference is the polymer dimension where the addition of soluble chains expectedly leads to longer polymer chains for P2 (P1: M̅_n = 88200, M̅_w = 188700, Đ = 2.14, DP = 111; P2: M̅_n = 147000, M̅_w = 327000, Đ = 2.23, DP = 133). However, unexpected differences in photophysical properties exist despite their structural similarities. First, P2 exhibits a higher fluorescence intensity and lifetime (τ_F ∼ 1 ns) with respect to that for P1 (τ_F ∼ 11 ps), despite the fact that alkyl chains are known to deactivate excited states (“loose bolt effect”). Second, P2 exhibits concurrently a rare case of higher energy fluorescence associated with an upper S_n excited state, which is not observed in P1. The two photon absorption properties of P1 and P2 have been acquired and both exhibit modest or similar cross sections (53 < σ₂ < 89 GM, P1; 45 < σ₂ < 70 GM, P2; for laser power ranging from 252 to 327 GW/cm²) in comparison with other [Pt]-containing polymers.

Ultrafast Photoinduced Electron Transfers in Platinum(II)-Anthraquinone Diimine Polymer/PCBM Films. Frank Juvenal, Hu Lei, Adrien Schlachter, Paul-Ludovic Karsenti, and Pierre D. Harvey. The Journal of Physical Chemistry C, 2019, 123(9), 5289-5302. https://doi.org/10.1021/acs.jpcc.9b00334

Abstract: Two fluorescent polymers ([Pt]-(AQI(BMPA)_x))_n ([Pt] = trans-bis(ethynylbenzene)-bis(tributylphosphine)platinum(II); AQI = anthraquinone diimine; BMPA = bis(para-methoxyphenyl)amine), P1 (x = 1; τ_F ≤ 8 ps) and P2 (x = 2; τ_F = 10 ps, 298 K), were prepared and investigated as thin films in the presence of phenyl-C₆₁-butyric acid methyl ester (PCBM) to probe the photoinduced electron transfer processes using steady-state and time-resolved fluorescence and femtosecond-transient absorption spectroscopy (fs-TAS). P1 and P2 undergo an efficient oxidative photoinduced electron transfer (Px* + PCBM → Px^+• + PCBM^–•; x = 1, 2) in solution and as films. Based on fs-TAS, the time scale for the photogenerated charge separated state forms within the excitation pulse (i.e., ≤150 fs). During the course of this study, the nature of the lowest energy emissive excited state was identified as a charge transfer state defined as [Pt] → AQI (major component) and BMPA → AQI (minor component) with the aid of density functional theory (DFT) and time-dependent DFT computations.

Characterization and Minimization of Glaser Competitive Homocoupling in Sonogashira Porphyrin-Based Polycondensation. Loïc Tanguy, Ophélie Hétru, Adam Langlois, and Pierre D. Harvey. The Journal of Organic Chemistry, 2019, 84(6), 3590-3594. https://doi.org/10.1021/acs.joc.8b02596

Abstract: A porphyrin-containing polymer exhibiting various degrees of Glaser-Hay coupling is reported. Sonogashira polycondensation of zinc(II) (5,15-bis[3,4,5-tri(2-butyloctyl)phenyl]-10,20-bis(ethynyl)porphyrinate) with N,N′-bis(p-iodobenzene)-2,3,5,6-tetrafluorobenzoquinone-1,4-diimine (fQI) is found to be prone to homocoupling, a problem underestimated in the literature. ¹H NMR and photophysical analysis are used to assess the ratio of Glaser versus Sonogashira couplings. Optimized conditions to perform Glaser-free Sonogashira polycondensations are provided, and the optimization increases M_n from 9700 to 18 900. Applied to a conjugated polymer, it shows both decreasing homocoupling and 180% enhancement in M_n.

The photochemical and photophysical properties of the [[M₃(dppm)₃(CO)]]²⁺ clusters (M = Pd, Pt). Pierre D. Harvey. Journal of Organometallic Chemistry, 2019, 880, 175-186. https://doi.org/10.1016/j.jorganchem.2018.11.009

Abstract: This title clusters were first reported by Puddephatt and his group over 30 years ago, and their reactivity was thoroughly investigated, namely including the oxidative additions of inorganic and organic substrates and host-guest associations. Then, Mugnier and Harvey, scrutinized in large detail the rich electrochemical behaviour of the [[Pd₃(dppm)₃(CO)]]²⁺ cluster, [Pd₃²⁺], namely of the reduced paramagnetic species [Pd₃^•+] during the 1997–2010 period. Concurrently, Harvey and his group conducted an in depth study, starting about 2008 until now, of the rather equally rich photophysical properties of both [M₃²⁺] (M = Pd, Pt) clusters. This mini-review of 39 references focusses on these properties, which have never been reviewed before. Their excited state properties such as the presence of higher and lower energy triplet excited states, triplet-triplet energy transfers in assemblies and upconversion, as well as the strong electron acceptor behaviour of [Pd₃²⁺] are discussed. Impressive ultrafast rates of electron transfer (<85 fs) between electron donors such as porphyrin and tetrabenzoporphyrin derivatives and this cluster have been reported.

Control of Structures and Emission Properties of (CuI)_n 2-Methyldithiane Coordination Polymers. Adrien Schlachter, Lydie Viau, Daniel J. Fortin, Lena Knauer, Carsten Strohmann, Michael Knorr, and Pierre D. Harvey. Inorganic Chemistry, 2018, 57(21), 13564-13576. https://doi.org/10.1021/acs.inorgchem.8b02168

Abstract: A structurally unique and strongly luminescent nonporous 3D coordination polymer (CP) [Cu₈I₈(methyldithiane)₄]_n, CP3, has been prepared in a quasi-anticipated manner from 2-methyl-1,3-dithiane, L1, and CuI. This CP incorporates an unprecedented Cu₈I₈ cluster built upon two side-fused open cubanes. The crystal structure of CP3 has been determined at 100, 150, 200, 250, 300, 350, and 400 K to study the temperature dependence of the Cu···Cu distances. Two other topological 1D and 2D CPs isomers of formula [{Cu₂I₂}(L1)₂]_n featuring dinuclear {Cu₂(μ₂-I)₂} rhomboids were also obtained independently by control of the reaction conditions. These two CPs convert into CP3 in hot PrCN, thus indicating that this latter material is the thermodynamic product. While CP1 and CP2 are not emissive, CP3 exhibits an intense luminescence due to the incorporation of the octanuclear Cu₈I₈ clusters as secondary building units within the network. The photophysical properties of CP3 have been investigated and rationalized by means of DFT and TDDFT computing. Furthermore, the thermal stability of these materials has been studied by ATG and DSC analyses. The Raman spectra of CP1-3 have been recorded in the solid state in the 50–500 cm^–1 region.

Cross Conjugated Organometallic Polymers Exhibiting Ultrafast Excitation Energy Channeling: Drastic Effect of the Connectivity. Hu Lei, Frank Juvenal, Paul-Ludovic Karsenti, Daniel J. Fortin, and Pierre D. Harvey. Macromolecular Chemistry and Physics, 2018, 219, 22, 1800354. https://doi.org/10.1002/macp.201800354

Abstract: A polymer composed of 2,6-diethynylanthraquinone diimine (AQI) and trans-bis(tributylphosphine)platinum(II), [Pt], flanked by one tetraphenylpalladium(II)porphyrin (TPPPd) and one para-nitrobenzene (C₆H₄NO₂) is prepared (P1: M_n = 57000, M_w = 124500, Đ = 2.18, DP = 52.5) and is studied by time-resolved emission spectroscopy and fs transient absorption spectroscopy (fs-TAS). A model polymer (AQI(C₆H₄NO₂)₂-[Pt])_nis used for comparison (P2: M_n = 88200, M_w = 188700, Đ = 2.14, DP = 111). Taking advantage of the dynamics of the excited states of [Pt] and TPPPd and those obtained for P1 and P2, it is shown that the excitation energy absorbed by the central polymer chain, (AQI-[Pt])_n, channels this energy very efficiently, to the pendent TPPPd with a rate of energy transfer, k_ET(S₁), larger than 2.3 × 10¹⁰ s⁻¹ for an energy transfer ¹(AQI-[Pt])* → TPPPd for P1 at 298 K based on the decrease of the fluorescence lifetime of the (AQI-[Pt])_nchain in P1 compared to P2. This rate is more accurately estimated by fs-TAS and is found to be 1.8 × 10¹¹ s⁻¹. This rate is ultrafast and is due to a large contribution of the Dexter mechanism across the imine bridge (CN).

Solid–Solid Phase Transitions in [trans-Pt(PMe₃)₂(C≡CC₆H₄R)₂]-Containing Materials (R = O(CH₂)_nH; n = 6, 9, 12, and 15). Gabriel Marineau-Plante, Daniel J. Fortin, Armand Soldera, and Pierre D. Harvey. Organometallics, 2018, 37(15), 2544-2552. https://doi.org/10.1021/acs.organomet.8b00304

Abstract: The title complexes were prepared in Hagihara conditions and were investigated by single crystal X-ray crystallography (n = 6, [Pt]C₆; n = 12, [Pt]C₁₂), X-ray powder diffraction (powder XRD), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA, [Pt]C₁₂), and steady-state and time-resolved solid state UV–vis and emission spectroscopy at 298 and 77 K. [Pt]C₆ complex exhibits no phase change with the temperature. Concurrently, [Pt]C₉ (n = 9) and [Pt]C₁₂ complexes exhibit an irreversible T_endo values of 104 and 119 °C, respectively, associated with a thermal annealing. Finally, [Pt]C₁₅ (n = 15) complex exhibit a reversible thermal processes with a large hysteresis (T_endo = 126 °C, T_exo = 140 °C) followed by a glass transition (T_endo = 146 °C, T_exo = 69 °C) as depicted by DSC. These phase changes are accompanied by a decrease in triplet excited state lifetimes upon cycling the sample temperature over and under the transition temperatures. These various thermal processes induce a significant decrease in emission lifetimes, strongly suggesting the presence of a reorganization of the complexes in the solid state favoring more chain-chromophore contacts, thus promoting nonradiative “knocking” processes.

Nonfullerene Polymer Solar Cells Reaching a 9.29% Efficiency Using a BODIPY-Thiophene Backboned Donor Material. Léo Bucher, Nicolas Desbois, Pierre D. Harvey, Claude P. Gros, Rajneesh Misra, and Ganesh D. Sharma. ACS Applied Energy Materials, 2018, 1(7), 3359-3368. https://doi.org/10.1021/acsaem.8b00535

Abstract: A conjugated polymer donor containing BODIPY-thiophene dyads in the backbone, P(BdP-EHT), combined with a low bandgap nonfullerene acceptor (SMDPP) consisting of carbazole and diketopyrrolopyrrole units linked with a tetracyanobutadiene acceptor π-linker, was used to design bulk heterojunction polymer solar cells. After the optimization of the donor to acceptor weight ratio and solvent vapor annealing of the P(BdP-EHT):SMDPP active layer, the resulting polymer solar cell showed an overall power conversion efficiency of 9.29%, which is significantly higher than that for the polymer solar cell based on PC₇₁BM (7.41%) processed under identical conditions. This improved power conversion efficiency is attributed to enhanced values of short circuit photocurrent and open circuit voltage, the better light harvesting efficiency of the P(BdP-EHT):SMDPP active layer in the near-infrared region, and the higher Lowest Unoccupied Molecular Orbital (LUMO) energy level of the SMDPP as compared to PC₇₁BM, combined. Moreover, energy loss in the device based on P(BdP-EHT):SMDPP active layer is significantly low (0.48 eV) as compared to P(BdP-EHT):PC₇₁BM counterpart (0.78 eV). Since the P(BdP-EHT) consists of triple bond, a linker may be beneficial for the stability of the polymer solar cells.

Completely Unexpected Coordination Selectivity of Copper Iodide for Thioether Over Ethynyl. Antoine Bonnot, Frank Juvenal, Adrien Schlachter, Daniel J. Fortin, and Pierre D. Harvey. Chemistry Africa, 2018, 1, 67-77. https://doi.org/10.1007/s42250-018-0004-x

Abstract: The reactivity of the tetradentate ligand bis(p-thiomethylphenylacetylene) (MeSC₆H₄C≡C–C≡CC₆H₄SMe; L2) towards the CuI salt is compared to that for the known organometallic analogue trans-bis(p-thiomethylethynylbenzene)bis(trimethyl-phosphine)platinum(II) (trans-Pt(PMe₃)₂(C≡CC₆H₄SMe)₂; L1). While L1 with CuI form a highly luminescent porous 2D coordination polymer (CP) of general formula ([Cu₄I₄]L1 · EtCN)_n (CP1; Juvenal et al. in Inorg Chem 55:11096–11109, 2016) exhibiting both Cu(η²–C≡C) and Cu–S bonds, L2 reacts with CuI to produce a luminescent non-porous 2D CP exhibiting the general formula ([Cu₄I₄]{L2}₃)_n, CP2, which does not use the highly expected Cu(η²–C≡C) linkage, relying strictly upon Cu–S coordination. An examination of the X-ray structures for both L2 and CP2 indicates that CP2 network is built upon an expansion of the L2 lattice (plane sliding and slight L2–L2 distance separation) resembling to a sort of template effect. CP2 has been characterized by TGA, UV–Vis, emission spectroscopy, and photophysics, which are accompanied by DFT and TDDFT computations.

A “Flexible” Rigid Rod, trans-Pt(PMe₃)₂(C≡CC₆H₄CN)₂ (L1), to Form 2D [{Cu₂(μ₂-X)₂}₂(μ₄-L1)]_n Polymers (X = Br, I) Exhibiting the Largest Bathochromic Emissions. Frank Juvenal, Daniel J. Fortin, and Pierre D. Harvey. Inorganic Chemistry, 2018, 57(12), 7208-7221. https://doi.org/10.1021/acs.inorgchem.8b00899

Abstract: The trans-Pt(PMe₃)₂(C≡CC₆H₄CN)₂ organometallic ligand L1, which is prepared from 4-ethynylbenzonitrile and cis-Pt(PMe₃)₂Cl₂, binds CuX salts to form two strongly luminescent two-dimensional coordination polymers (CPs) [{Cu₂(μ₂-X)₂}₂(μ₄-L1)]_n (X = I, CP1; X = Br, CP2). The emission quantum yields, Φ_e ≈ 30% at 298 K, are the largest ones for all CPs built upon the trans-Pt(PMe₃)₂(C≡CC₆H₄X)₂ motifs (X = SMe, CN). X-ray crystallography reveals that, to accommodate these layered CPs, L1 must undergo major distortions of the C≡C–C angles (∼159°) and significant rotations about the Pt-CC bonds, so that the dihedral angles made by the two aromatic planes is 90° in a quasi-identical manner for both CPs. Together, these two features represent the largest distortion for trans-Pt(PMe₃)₂(C≡CC₆H₄X)₂ complexes among all of the CPs built upon this type of ligand (2 of 16 entries). Concurrently, CP1 and CP2 also exhibit the most red-shifted emissions (λ_max = 650 and 640 nm, respectively) known for this type of chromophore at room temperature. The {Cu₂(μ₂-X)₂} rhomboids adopt the trans- (X = I, common) and cis-geometries (X = Br, extremely rare) making them “isomers” if excluding the fact that the halides are different. Density functional theory (DFT) and time-dependent DFT suggest that the triplet emissive excited state is metal/halide-to-ligand charge transfer in both cases despite this difference in rhomboid geometry.

What does it take to induce equilibrium in bidirectional energy transfers? Di Gao, Shawkat M. Aly, Paul-Ludovic Karsenti, and Pierre D. Harvey. Physical Chemistry Chemical Physics, 2018, 20, 13682-13692. https://doi.org/10.1039/C7CP07879J

Abstract: Two dyads built with a co-facial slipped bis(zinc(II)porphyrin), a free base and a bridge, [Zn₂]–bridge–[Fb] (bridge = C₆H₄C≡C, 1 and C₆H₄C≡CC₆H₄, 2), exhibit S₁ energy equilibrium [Zn₂]* ↔ [Fb]* at 298 K, an extremely rare situation, which depends on the degree of MO coupling between the units. At 77 K, 2 becomes bi-directional due to the two large C₆H₄–[Zn₂] and C₆H₄–[Fb] dihedral angles.

Is π-Stacking Prone To Accelerate Singlet–Singlet Energy Transfers? Di Gao, Shawkat M. Aly, Paul-Ludovic Karsenti, and Pierre D. Harvey. Inorganic Chemistry, 2018, 57(8), 4291-4300. https://doi.org/10.1021/acs.inorgchem.7b03050

Abstract: π-Stacking is the most common structural feature that dictates the optical and electronic properties of chromophores in the solid state. Herein, a unidirectional singlet–singlet energy-transfer dyad has been designed to test the effect of π-stacking of zinc(II) porphyrin, [Zn₂], as a slipped dimer acceptor using a BODIPY unit, [bod], as the donor, bridged by the linker C₆H₄C≡CC₆H₄. The rate of singlet energy transfer, k_ET(S₁), at 298 K (k_ET(S₁) = 4.5 × 10¹⁰ s^–1) extracted through the change in fluorescence lifetime, τ_F, of [bod] in the presence (27.1 ps) and the absence of [Zn₂] (4.61 ns) from Streak camera measurements, and the rise time of the acceptor signal in femtosecond transient absorption spectra (22.0 ps), is faster than most literature cases where no π-stacking effect exists (i.e., monoporphyrin units). At 77 K, the τ_F of [bod] increases to 45.3 ps, indicating that k_ET(S₁) decreases by 2-fold (2.2 × 10¹⁰ s^–1), a value similar to most values reported in the literature, thus suggesting that the higher value at 298 K is thermally promoted at a higher temperature.

Multiply “trapped” ³[trans-Pt(PR₃)₂(CCC₆H₄X)₂]* conformers in rigid media. Gabriel Marineau-Plante, Frank Juvenal, Adam Langlois, Daniel J. Fortin, Armand Soldera, and Pierre D. Harvey. Chemical Communications, 2018, 54, 976-979. https://doi.org/10.1039/C7CC09503A

Abstract: The complexes (R = Me, Et, Bu; X = H, SMe) exhibit well-defined multi-exponential emissions (2–4 components) in the solid state at 77 and 298 K and in 2MeTHF glasses at 77 K due to multiple frozen conformers exhibiting variable dihedral angles formed by the PtP₂C₂ and C₆H₄ planes. The demonstration was made using X-ray crystallography at various temperatures where different sites are present in the samples, and using geometry optimization (DFT computations) where various stable conformers are noted.

Triplet energy vs. electron transfers in porphyrin- andt etrabenzoporphyrin-carboxylates/Pd₃(dppm)₃(CO)²⁺ cluster assemblies; a question of negative charge. Peng Luo, Paul-Ludovic Karsenti, Benoit Marsan, and Pierre D. Harvey. New Journal of Chemistry, 2018, 42, 8160-8168. https://doi.org/10.1039/C7NJ03943C

Abstract: Two tetracarboxylatetetrabenzoporphyrinzinc(II), TCPBP (9,18,27,36-tetrakis-meso-(4-carboxyphenyl)tetrabenzoporphyrinatozinc(II)) and TCPEBP (9,18,27,36-tetra-(4-carboxyphenylethynyl)tetrabenzoporphyrinatozinc(II)), and their two corresponding porphyrins, TCPP (tetrakis-meso-(4-carboxyphenyl)porphyrinatozinc(II)) and TCPEP (5,10,15,20-tetra-(4-carboxyphenylethynyl)porphyrinatozinc(II)) as sodium salts in a 1 : 1 mixture of 2MeTHF/MeOH at 77 K exhibit phosphorescence in the near-IR region with maxima ranging from 785 to 1005 nm. The position of these triplet state emissions has been corroborated from DFT (B3LYP) by calculating the total energy difference between the ground, S₀, and lowest energy triplet excited state T₁ (the calculated position ranges from 797 to 1041 nm). At both temperatures, 77 and 298 K, these dyes make ionic driven host–guest assemblies with the unsaturated redox-active cluster Pd₃(dppm)₃(CO)²⁺ ([Pd₃²⁺], dppm = Ph₂PCH₂PPh₂ as a PF₆⁻ salt). The formation of these assemblies is accompanied by a quenching of the phosphorescence band, without changing the emission lifetime. This phenomenon is consistent with the formation of the non-emissive assemblies dye⋯[Pd₃²⁺]_x according to dye + [Pd₃²⁺] → dye⋯[Pd₃²⁺]_x (x = 1–4), where only the porphyrin and tetrabenzoporphyrin dyes are phosphorescent. Quenching analysis confirmed that a static quenching mechanism operates. In one case, the quenching rate (k_Q) has been evaluated from transient absorption spectroscopy (TAS) where the signal associated with the dye's triplet state exhibits a very short lifetime τ(T₁), thus corroborating the efficient quenching. The quenching rate (1/τ(T₁)) is much faster (3.0 × 10⁸ s⁻¹) than that expected for the other dye⋯[Pd₃²⁺]_x assemblies in the literature (∼10⁴ s⁻¹) known for their triplet–triplet energy transfer. Based on the excited state driving force argumentation for oxidative quenching, this fast process is assigned to a predominant photo-induced electron transfer (³dye* + [Pd₃²⁺] → dye⁺˙ + [Pd₃⁺˙]).

Azophenine as Central Core for Efficient Light Harvesting Devices. Hu Lei, Paul-Ludovic Karsenti, and Pierre D. Harvey. ChemPhysChem, 2018, 19(5), 596-611. https://doi.org/10.1002/cphc.201701183

Abstract: The notoriously non-luminescent uncycled azophenine (Q) was harnessed with Bodipy and zinc(II)porphyrin antennas to probe its fluorescence properties, its ability to act as a singlet excited state energy acceptor and to mediate the transfer. Two near-IR emissions are depicted from time-resolved fluorescence spectroscopy, which are most likely due to the presence of tautomers of very similar calculated total energies (350 cm⁻¹; DFT; B3LYP). The rates for energy transfer, k_ET(S₁), for ¹Bodipy*→Q are in the order of 10¹⁰–10¹¹ s⁻¹ and are surprisingly fast when considering the low absorptivity properties of the lowest energy charge transfer excited state of azophenine. The rational is provided by the calculated frontier molecular orbitals (MOs) which show atomic contributions in the C₆H₄C≡CC₆H₄ arms, thus favoring the double electron exchange mechanism. In the mixed-antenna Bodipy–porphyrin star molecule, the rate for ¹Bodipy*→porphyrin has also been evaluated (≈16×10¹⁰ s⁻¹) and is among the fastest rates reported for Bodipy–zinc(II)porphyrin pairs. This astonishing result is again explained from the atomic contributions of the C₆H₄C≡CC₆H₄ and C≡CC₆H₄ arms thus favouring the Dexter process. Here, for the first time, this process is found to be sensitively temperature-dependent. The azophenine turns out to be excellent for electronic communication.

Porphyrin Antenna-Enriched BODIPY–Thiophene Copolymer for Efficient Solar Cells. Léo Bucher, Nicolas Desbois, Pierre D. Harvey, Claude P. Gros, and Ganesh D. Sharma. ACS Applied Materials and Interfaces, 2018, 10(1), 992-1004. https://doi.org/10.1021/acsami.7b16112

Abstract: Low bandgap A−π–D copolymer, P(BdP-DEHT), consisting of alternating BOronDIPYrromethene (BODIPY) and thiophene units bridged by ethynyl linkers, and its porphyrin-enriched analogue, P(BdP/Por-DEHT), were prepared, and their optical and electrochemical properties were studied. P(BdP-DEHT) exhibits strong absorption in the 500–800 nm range with an optical bandgap of 1.74 eV. On the basis of cyclic voltammetry, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels are evaluated to be −5.40 and −3.66 eV, respectively. After the anchoring of zinc(II) porphyrin on the BODIPY unit, P(BdP/Por-DEHT) displays broadened absorption, thanks to porphyrins, and the optical bandgap decreases to 1.59 eV because of extension of BODIPY conjugation. The resulting estimated HOMO and LUMO energy levels, respectively, move to −5.32 and −3.73 eV. After optimization of the P(BdP-DEHT) or P(BdP/Por-DEHT) to PC₇₁BM weight ratio to 1:2 in dichlorobenzene solution, the bulk heterojunction polymer solar cells show overall power conversion efficiencies (PCEs) of 3.03 and 3.86%, respectively. After solvent vapor annealing (SVA) treatment in CH₂Cl₂ for 40 s, the PCEs increased to 7.40% [V_oc of 0.95 V, J_sc of 12.77 mA/cm², and fill factor (FF) of 0.61 with energy loss of 0.79 eV] and 8.79% (V_oc of 0.92 V, J_sc of 14.48 mA/cm², and FF of 0.66 with energy loss of 0.67 eV). The increase in the PCE for P(BdP/Por-DEHT)-based devices is mainly attributed to the enhancement in J_sc and FF, which may be related to the broader absorption spectra, lower band gap, and better charge transport of P(BdP/Por-DEHT) compared to P(BdP-DEHT). This could also be related to the optimized nanoscale morphology of the active layer for both efficient exciton dissociation and charge transport toward the electrodes and a balanced charge transport in the device, induced by the SVA treatment of the active layer.

Photovoltaic Properties of a Porphyrin-Containing Polymer as Donor in Bulk Heterojunction Solar Cells With Low Energy Loss. Léo Bucher, Loïc Tanguy, Nicolas Desbois, Paul-Ludovic Karsenti, Pierre D. Harvey, Claude P. Gros, and Ganesh D. Sharma. Solar RRL, 2018, 2(1), 1700168. https://doi.org/10.1002/solr.201700168

Abstract: A low bandgap D-π-A polymer (PPDPP; D = Zn-porphyrin, A = diketopyrrolopyrrole, π = ethynyle linker) has been synthesized and used as an electron donor for the fabrication of solution processed bulk heterojunction polymer solar cells (PSCs). PC₇₁BM is used as the electron acceptor. After the optimization of the PPDPP: PC₇₁BM weight ratio in 2-methyltetrahydrofuran (2-MeTHF), the PSC based on PPDPP: PC₇₁BM (1:2) showed an overall power conversion efficiency (PCE) of 4.18% with J_sc = 9.75 mA cm⁻², V_oc = 0.78 V, and FF = 0.54. After the thermal annealing (TA) and subsequent solvent vapor annealing (SVA) of the active layer, the resulting device showed an overall PCE of 6.44% (J_sc = 13.18 mA cm⁻², V_oc = 0.74 V, and FF = 0.66) with a small voltage loss of 0.51 eV. The improvement in PCE after the TA and SVA treatment of the active layer is attributed to an enhancement of J_sc and FF related to a more favorable nanoscale morphology for the exciton dissociation and charge transport as evidenced by the increased hole mobility.

The trans-Bis(p-thioetherphenylacetynyl)bis(phosphine)platinum(II) Ligands: A Step towards Predictability and Crystal Design. Frank Juvenal, Antoine Bonnot, Daniel J. Fortin, and Pierre D. Harvey. ACS Omega, 2017, 2(10), 7433-7443. https://doi.org/10.1021/acsomega.7b01352

Abstract: Two organometallic ligands L1 (trans-[p-MeSC₆H₄C≡C-Pt(PR₃)₂-C≡CC₆H₄SMe; R = Me]) and L2 (R = Et) react with CuX salts (X = Cl, Br, I) in MeCN to form one-dimensional (1D) or two-dimensional (2D) coordination polymers (CPs). The clusters formed with copper halide can either be step cubane Cu₄I₄, rhomboids Cu₂X₂, or simply CuI. The formed CPs with L1, which is less sterically demanding than L2, exhibit a crystallization solvent molecule (MeCN), whereas those formed with L2 do not incorporate MeCN molecules in the lattice. These CPs were characterized by X-ray crystallography, thermogravimetric analysis, IR, Raman, absorption, and emission spectra as well as photophysical measurements in the presence and absence of crystallization MeCN molecules for those CPs with the solvent in the lattice (i.e., [(Cu₄I₄)L1·MeCN]_n (CP1), [(Cu₂Br₂)L1·2MeCN]_n (CP3), and [(Cu₂Cl₂)L1·MeCN]_n (CP5)). The crystallization molecules were removed under vacuum to evaluate the porosity of the materials by Brunauer–Emmett–Teller (N₂ at 77 K). The 2D CP shows a reversible type 1 adsorption isotherm for both CO₂ and N₂, indicative of microporosity, whereas the 1D CPs do not capture more solvent molecules or CO₂.

Platinum Complexes of N,N′,N″,N‴-Diboronazophenines. Hu Lei, Shawkat M. Aly, Paul-Ludovic Karsenti, Daniel J. Fortin, and Pierre D. Harvey. Inorganic Chemistry, 2017, 56(21), 13140-1351. https://doi.org/10.1021/acs.inorgchem.7b01942

Abstract: Azophenine, (α-C₆H₅NH)₂(C₆H₅–N═C₆H₂═N–C₆H₅), well known to be non-emissive, was rigidified by replacing two amine protons by two difluoroboranes (BF₂⁺) and further functionalized at the para-positions of the phenyl groups by luminescent trans-ArC≡C–Pt(PR₃)₂-C≡C ([Pt]) arms [Ar = C₆H₄ (R = Et), hexa(n-hexyl)truxene) (Tru; R = Bu)]. Two effects are reported. First, the linking of these [Pt] arms with the central azophenine (C₆H₄–N═C₆H₂(NH)₂═N–C₆H₄; Q) generates very low energy charge-transfer (CT) singlet and triplet excited states (^3,1([Pt]-to-Q)*) with absorption bands extending all the way to 800 nm. Second, the rigidification of azophenine by the incorporation of BF₂⁺ units renders the low-lying CT singlet state clearly emissive at 298 and 77 K in the near-IR region. DFT computations place the triplet emission in the 1200–1400 nm range, but no phosphorescence was detected. The photophysical properties are investigated, and circumstantial evidence for slow triplet energy transfers, ³Tru* → Q, is provided.

Porphyrins and BODIPY as Building Blocks for Efficient Donor Materials in Bulk Heterojunction Solar Cells. Léo Bucher, Nicolas Desbois, Pierre D. Harvey, Ganesh D. Sharma, and Claude P. Gros. Solar RRL, 2017, 1(12), 1700127. https://doi.org/10.1002/solr.201700127

Abstract: Advances in the synthesis and application of highly efficient polymers and small molecules over the last two decades have enabled the rapid advancement in the development of organic solar cells and photovoltaic technology as a promising alternative to conventional solar cells, based on silicon and other inorganic semiconducting materials. Among the different types of organic semiconducting materials, porphyrins and BODIPY-based small molecules and conjugated polymers attract high interest as efficient semiconducting organic materials for dye sensitized solar cells and bulk heterojunction organic solar cells. The highest power conversion efficiency exceeding 9% has been reported so far for porphyrin small molecules and 8.60% for conjugated polymers based on porphyrins. On the other hand, small molecules and conjugated polymers based on BODIPY moiety have been successfully used as donor materials for solution processed bulk heterojunction organic solar cells, and the resultant devices showed power conversion efficiencies exceeding 5.5%. In this article, the development of molecular design of porphyrins and BODIPY small molecules and polymers for bulk heterojunction organic solar cells are reviewed, and a guideline for the structure-performance relationship is provided.

Organometallic and Coordination Polymers, and Linear and Star Oligomers Using the trans-Pt(PR₃)₂(C≡C)₂ Linker. Pierre D. Harvey. Journal of Inorganic and Organometallic Polymers and Materials, 2017, 27, 3-38. https://doi.org/10.1007/s10904-017-0673-y

Abstract: This review article presents the advances made by the Harvey group over the past 10 years on the development of new functional materials using the trans-Pt(PR₃)₂(C≡C)₂ fragment, [Pt], mainly targeting photonic properties. The presented topics include the synthesis, electronic communication across the chain, polymers bearing chiral P-centers, electroactive polymers, photo-induced electron transfers, triplet excited state energy transfers, formation of charge transfer excited states for push–pull polymers, trans-Pt(PR₃)₂(C≡C)₂-containing polyaniline, star molecules and coordination polymers. This research aims at designing photonic devices, such as solar cells and light emitting diodes, and evaluating their performances, as well as sensors for gases, namely CO₂, and small molecules. The photophysical properties of the related trans-(C≡C)Pt(dppm)₂Pt(C≡C) fragment ([Pt₂]) is presented for comparison purposes. It turns out that the Pt(I)–Pt(I) bond is excellent for electronic communication but is also particularly sensitive to oxidative additions, hence limiting its applications.

Increasing the lifetimes of charge separated states in porphyrin–fullerene polyads. Di Gao, Shawkat M. Aly, Paul-Ludovic Karsenti, Gessie Brisard, and Pierre D. Harvey. Physical Chemistry Chemical Physics, 2017, 19, 24018-24028. https://doi.org/10.1039/C7CP04193D

Abstract: Two linear polyads were designed using zinc(II)porphyrin, [ZnP], and N-methyl-2-phenyl-3,4-fullero-pyrrolidine (C₆₀) where C₆₀ is dangling either at the terminal position of [ZnP]–C₆H₄––C₆H₄–[ZnP]–C₆₀ (1) or at the central position of [ZnP]–C₆H₄––C₆H₄–[ZnP(C₆₀)]–C₆H₄––C₆H₄–[ZnP] (2) in order to test whether the fact of having one or two side electron donors influences the rate of electron transfer, k_et. These polyads were studied using cyclic voltammograms, DFT computations, steady state and time-resolved fluorescence spectroscopy, and femtosecond transient absorption spectroscopy (fs-TAS). Photo-induced electron transfer confirmed by the detection of the charge separated state [ZnP˙⁺]/C₆₀˙⁻ from fs-TAS occurs with rates (k_et) of 3–4 × 10¹⁰ s⁻¹ whereas the charge recombinations (CRs) are found to produce the [ZnP] ground state via two pathways (central [ZnP˙⁺]/C₆₀˙⁻ (ps) and terminal central [ZnP˙⁺]/C₆₀˙⁻ (ns) producing [¹ZnP] (ground state) and [³ZnP*]). The formation of the T₁ species is more predominant for 2.

Synthesis and photovoltaic properties of new ruthenium(II)-bis(aryleneethynylene) complexes. Qian Lui, Cheuk-Lam Ho, Nianyong Zhu, Yingying Fu, Zhiyuan Xie, Lixiang Wang, Pierre D. Harvey, Wai-Yeung Wong. Journal of Organometallic Chemistry, 2017, 846, 277-286. https://doi.org/10.1016/j.jorganchem.2017.06.026

Abstract: A new series of small-molecular ruthenium(II)-diynes trans-Ru(dppe)₂(C≡CAr)₂ (D1−D4) (dppe = Ph₂CH₂CH₂Ph₂; Ar = aromatic moiety) have been successfully designed, synthesized and characterized by photophysical, electrochemical and computational methods, and complexes D1 and D3 were crystallographically characterized. The optical and time-dependent density functional theory studies showed that the absorption ability of these complexes was significantly enhanced by incorporating the stronger electron-donor groups. The effect of different electron-donor groups in these metallo-organic complexes on the optoelectronic and photovoltaic properties was also examined. In this work, benzothiadiazole as the electron acceptor and triphenylamine and/or thiophene as the electron donor were introduced in these complexes, which were found to have optimal energy bandgaps spanning from 1.70 to 1.83 eV and broad absorption bands within 300–700 nm, rendering them good electron donor materials to blend with [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₀BM) in the fabrication of the solution-processed bulk heterojunction (BHJ) solar cells. The best power conversion efficiency (PCE) of 0.66% was achieved, which is the highest PCE in ruthenium(II)-containing BHJ solar cells to date.

Rendering cross-conjugated azophenine derivatives emissive to probe the silent photophysical properties of emeraldine. Hu Lei, Adam Langlois, Daniel J. Fortin, Paul-Ludovic Karsenti, Sawkat M. Aly, and Pierre D. Harvey. Physical Chemistry Chemical Physics, 2017, 19, 21532-21539. https://doi.org/10.1039/C7CP04102K

Abstract: An azophenine derivative was synthesized by coupling truxene and azophenine via the copper-free Sonagashira reaction using Pd₂(dba)₃ and As(PPh)₃ as catalysts. The crystal structure of this heavy azophenine model (∼4000) was made and the identity of the structure was confirmed. By introducing truxene groups into this cross-conjugated structure, the deactivating rotations around the NH–C₆H₄ bonds were slowed down, which rendered this derivative near-IR emissive at 298 K. This species provided then the appropriate spectral and kinetic signatures for knowing where and what to look for in emeraldine, which was called non-emissive. Besides, two other compounds were also synthesized as models for this azophenine derivative for comparison and interpretation purposes.

Ferrocene–BODIPYmerocyanine dyads: new NIR absorbing platforms with optical properties susceptible to protonation. Yuriy V. Zatsikha, Natalia O.Didukh, Adrien C. Schlachter, Paul-Ludovic Karsenti, Yuriy P. Kovtun, Pierre D. Harvey, and Victor N. Nemykin. Chemical Communications, 2017, 53, 7612-7615. https://doi.org/10.1039/C7CC03332J

Abstract: Ferrocene–BODIPYmerocyanine dyads 5 and 6 were prepared and characterized by a variety of spectroscopic, electrochemical, and theoretical methods. Experimental and theoretical data on these NIR absorbing compounds are suggestive of unusual susceptibility (for BODIPY chromophores) of the delocalized π-system in 5 and 6 to protonation and low-potential oxidation of their π-systems.

Application of the boron center for the design of a covalently bonded closely spaced triad of porphyrin-fullerene mediated by dipyrromethane. Di Gao, Shawkat M. Aly, Paul-Ludovic Karsenti, Gessie Brisard, and Pierre D. Harvey. Dalton Transactions, 2017, 46, 6278-6290. https://doi.org/10.1039/C7DT00472A

Abstract: Two novel triads had been designed through covalent bond connection of the boron dipyrromethane (BODIPY), free base porphyrin (H2P) or zinc(II) porphyrin (ZnP) and N-methyl-2-phenyl-3,4-fulleropyrrolidine (C₆₀) mediated by BODIPY. This closely spaced triad arrangement where porphyrin and fullerene are placed apart is anticipated to stabilize charge separation by separating the two radicals from each other. Two model polyads were synthesized with BODIPY and H2P or ZnP to investigate interaction between the two chromophores. Photo-excitation of the BODIPY triggered an efficient singlet energy transfer where the rates are found to be ∼10¹⁰–10¹¹ s⁻¹. For triads with C₆₀ fast electron transfer was confirmed by the detection of the C₆₀˙⁻ signature from femtosecond transient absorption (fs-TA) in ∼0.4–3 ps. The charge recombination is estimated to be in the nanosecond window. This indicates the convenience of this arrangement for stabilizing the charge-separated state.

Random Structural Modification of a Low-Band-Gap BODIPY-Based Polymer. Léo Bucher, Shawkat M. Aly, Nicolas Desbois, Paul-Ludovic Karsenti, Claude P. Gros, and Pierre D. Harvey. The Journal of Physical Chemistry C, 2017, 121, 12, 6478-6491. https://doi.org/10.1021/acs.jpcc.7b00117

Abstract: A BODIPY–thiophene polymer modified by extending conjugation of the BODIPY chromophore is reported. This modification induces tunability of energy levels and therefore absorption wavelengths in order to target lower energies.

A Very Low Band Gap Diketopyrrolopyrrole–Porphyrin Conjugated Polymer. Léo Bucher, Loïc Tanguy, Daniel J. Fortin, Nicolas Desbois, Pierre D. Harvey, Ganesh D. Sharma, and Claude P. Gros. ChemPlusChem, 2017, 82(4), 625-630. https://doi.org/10.1002/cplu.201700035Digital

Abstract: A porphyrin–diketopyrrolopyrrole-containing polymer (poly(porphyrin–diketopyrrolopyrrole) (PPDPP)) shows impressive molar absorption coefficients from λ=300 to 1000 nm. The photophysical and structural properties of PPDPP have been studied. With PPDPP as the electron donor and [6,6]-phenyl C₇₁ butyric acid methyl ester (PC₇₁BM) as the electron acceptor, the bulk heterojunction polymer solar cell showed overall power conversion efficiencies of 4.18 and 6.44 % for as-cast and two-step annealing processed PPDPP:PC₇₁BM (1:2) active layers, respectively. These results are quite impressive for porphyrin-containing polymers, especially when directly included in the π-conjugated backbone, and offer interesting perspectives for the design of new materials based on this chromophore.

Metal Dependence on the Bidirectionality and Reversibility of the Singlet Energy Transfer in Artificial Special Pair-Containing Dyads. Adam Langlois, Jean-Michel Camus, Paul-Ludovic Karsenti, Roger Guilard, and Pierre D. Harvey. Inorganic Chemistry, 2017, 56(5), 2506-2517. https://doi.org/10.1021/acs.inorgchem.6b02684

Abstract: The demetalation of a precursor dyad, 3, built upon a zinc(II)-containing artificial special pair and free-base antenna, leads to a new dyad, 4, for singlet energy transfer composed of cofacial free-base porphyrins (acceptor), [Fb]₂ bridged by a 1,4-C₆H₄ group to a free-base antenna (donor), [Fb]. This dyad exhibits the general structure [M]₂-C₆H₄-[Fb], where [M]₂ = [Fb]₂, and completes a series reported earlier, where [M]₂ = [Mg]₂ (2) and [Zn]₂ (3). The latter dyads exhibit a bidirectional energy-transfer process at 298 K for 2 and at 77 K for 3. Interestingly, a very scarce case of cycling process is observed for the zinc-containing dyad at 298 K. The newly reported compound 4 exhibits a quasi unidirectional process [Fb]*→[Fb]₂ (major, k_ET = 2 × 10¹¹ s^–1 at 298 K), where the remaining is [Fb]₂*→[Fb] (minor, k_ET = 8 × 10⁹ s^–1 at 298 K), thus completing all possibilities. The results are analyzed in terms of molecular orbital couplings (density functional theory computations), Förster resonance energy transfer parameters, and temperature dependence of the decay traces. This study brings major insights about artificial special pair-containing dyads and clearly contributes to a better understanding of the communication between the two main components of our models and those already described in the literature.

Excited State N−H Tautomer Selectivity in the Singlet Energy Transfer of a Zinc(II)-Porphyrin–Truxene–Corrole Assembly. Adam Langlois, Hai-Jun Xu, Paul-Ludovic Karsenti, Claude P. Gros, Pierre D. Harvey. Chemistry - a European Journal, 2017, 23(21), 5010-5022. https://doi.org/10.1002/chem.201605909

Abstract: An original corrole-containing polyad for S₁ energy transfer, in which one zinc(II)-porphyrin donor is linked to two free-base corrole acceptors by a truxene linker, is reported. This polyad exhibits a rapid zinc(II)-porphyrin*→free-base corrole transfer (4.83×10¹⁰ s⁻¹; 298 K), even faster than the tautomerization in the excited state processes taking advantage of the good electronic communication provided by the truxene bridge. Importantly, the energy transfer process shows approximately 3-fold selectivity for one corrole N−H tautomer over the other even at low temperature (77 K). This selectivity is due to the difference in the J-integral being effective in both the Förster and Dexter mechanisms. The data are rationalized by DFT computations.

Luminescent Organometallic Complexes Built upon the Nonemissive Azophenine. Hu Lei, Shawkat M. Aly, Paul-Ludovic Karsenti, Daniel J. Fortin, and Pierre D. Harvey. Organometallics, 2017, 36(3), 572-581. https://doi.org/10.1021/acs.organomet.6b00789

Abstract: Azophenine, C₆H₂(═NPh)₂(NHPh)₂, is renowned to be nonemissive in solution or in the solid state at 298 and 77 K. It was rendered luminescent in solution at room temperature without using any cyclization strategy of the N^∧N end by anchoring two or four trans-RC≡CPt(PBu₃)₂(C≡C) units (R = hexa-n-hexyltruxene (Tru)) on the azophenine. Complexes of the general formulas C₆H₂(═NC₆H₄C≡CSiMe₃)₂(NHPtTru)₂ (DiPtTruQ) and C₆H₂(═NPtTru)₂(NHPtTru)₂(TertPtTruQ), where Pt = trans-C₆H₄C≡CPt(PBu₃)₂C≡C, exhibit fluorescence (420 nm) and phosphorescence (512 nm) bands arising from upper localized ππ*/C₆H₄C≡C to TruC≡C charge transfer singlet and triplet excited states in 2MeTHF at 298 and 77 K. This latter assignment is based on DFT computations (B3LYP). Moreover, DiPtTru and TertPtTru exhibit low-energy absorption bands with maxima in the 470–485 nm range extending all the way to 600–650 nm. These spectral features are associated with charge transfer (CT) excited states: namely, TruPt → Q (Q = C₆H₂N₂(NH)₂). No emission band (fluorescence or phosphorescence) associated with these CT states has been detected at 298 K, but weak fluorescence bands (λ_max ∼750 nm) decaying on the picosecond time scale have been observed in both cases. Biexponential decays were also often noted and likely reflect the presence of the possible conformers associated with the two possible dihedral angles made by the C₆H₄ plane and the central C₆H₂N₂(NH)₂ core. No evidence for electron transfer between the TruPt arms and Q was observed.

Ultrafast energy and electron transfers in structurally well addressable BODIPY-porphyrin-fullerene polyads. Di Gao, Shawkat M. Aly, Paul-Ludovic Karsenti, Gessie Brisard, and Pierre D. Harvey. Physical Chemistry Chemical Physics, 2017, 19, 2926-2939. https://doi.org/10.1039/C6CP08000F

Abstract: Two electron transfer polyads built upon [C₆₀]–[ZnP]–[BODIPY] (1) and [ZnP]–[ZnP](–[BODIPY])(–[C₆₀]) (2), where [C₆₀] = N-methyl-2-phenyl-3,4-fulleropyrrolidine, [BODIPY] = boron dipyrromethane, and [ZnP] = zinc(II) porphyrin, were synthesized along with their corresponding energy transfer polyads [ZnP]–[BODIPY] (1a) and [ZnP]–[ZnP]–[BODIPY] (2a) as well as relevant models. These polyads were studied using cyclic voltammetry, DFT computations, steady state and time-resolved fluorescence spectroscopy, and fs transient absorption spectroscopy. The rates for energy transfer, k_ET, [BODIPY]* → [ZnP] are ∼2.8 × 10¹⁰ s⁻¹ for both 1a and 2a, with an efficiency of 99%. Concurrently, the fast appearance of the [C₆₀]⁻˙ anion for 1 and 2 indicates that the charge separation occurs on the 20–30 ps timescale with the rates of electron transfer, k_et, [ZnP]*/[C₆₀] → [ZnP]⁺˙/[C₆₀]⁻˙ of ∼0.9 × 10¹⁰ to ∼3.8 × 10¹⁰ s⁻¹. The latter value is among the fastest for these types of polyads. Conversely, the charge recombination operates on the ns timescale. These rates are comparable to or faster than those reported for other more flexible [C₆₀]–[ZnP]–[BODIPY] polyads, which can be rationalized by the donor–acceptor separations.

Luminescent 1D- and 2D-Coordination Polymers Using CuX Salts (X = Cl, Br, I) and a Metal-Containing Dithioether Ligand. Frank Juvenal, Adam Langlois, Antoine Bonnot, Daniel Fortin, and Pierre D. Harvey. Inorganic Chemistry, 2016, 55(21), 11096-11109. https://doi.org/10.1021/acs.inorgchem.6b01703

Abstract: The organometallic synthon trans-[p-MeSC₆H₄C≡C-Pt(PMe₃)₂-C≡CC₆H₄SMe] (L1) reacts with CuX (X = Cl, Br, I) in PrCN and PhCN to form 1D- or 2D-coordination polymers (CP) with a very high degree of variability of features. The copper-halide unit can be either the rhomboids Cu₂X₂ fragments or the step cubane Cu₄I₄. The CP’s may also incorporate a crystallization solvent molecule or not, which may be coordinated to copper or not. Their characterizations were performed by X-ray crystallography, thermal gravimetric analysis (TGA), and IR, absorption, and emission spectra as well as photophysical measurements in the presence and absence of solvent crystallization molecules. The nature of the singlet and triplet excited state was addressed using DFT and TDDFT computations, which turn out to be mainly ππ* with some minor MLCT (Cu₄I₄ → L1) contributions. The porosity of the materials has been evaluated by BET (N₂ at 77 K). The solvent-free 1D CP’s are not prone to capture solvent molecules or CO₂, but the efficiency for CO₂ absorption is best for the 2D CP, which exhibits the presence of clear cavities in the grid structure, after the removal of the crystallization molecules.

Ultrafast Singlet Energy Transfer in Porphyrin Dyads. Hervé Dekkiche, Antoine Buisson, Adam Langlois, Paul-Ludovic Karsenti, Laurent Ruhlmann, Pierre D. Harvey, and Romain Ruppert. Inorganic Chemistry, 2016, 55(20), 10329-10336. https://doi.org/10.1021/acs.inorgchem.6b01594

Abstract: A weakly fluorescent Pt-bridged dyad composed of zinc(II) porphyrin (Zn; donor) and free base (Fb; acceptor) has been designed and exhibits an ultrafast singlet energy transfer between porphyrins. The use of larger atoms within the central linker significantly increases the MO coupling between the two chromophores and inherently the electronic communication.

Cyclotriveratrylene-Containing Porphyrins. Jude Deschamps, Adam Langlois, Gaël Martin, Léo Bucher, Nicolas Desbois, Claude P. Gros, and Pierre D. Harvey. Inorganic Chemistry, 2016, 55(18), 9230-9239. https://doi.org/10.1021/acs.inorgchem.6b01261

Abstract: The C₃-symmetric cyclotriveratrylene (CTV) was covalently bonded via click chemistry to 1, 2, 3, and 6 zinc(II) porphyrin units to various host for C₆₀. The binding constants, K_a, were measured from the quenching of the porphyrin fluorescence by C₆₀. These constants vary between 400 and 4000 M^–1 and are considered weak. Computer modeling demonstrated that the zinc(II) porphyrin units, [Zn], exhibit a strong tendency to occupy the CTV cavity, hence blocking the access for C₆₀ to land on this site. Instead, the pincer of the type [Zn]----[Zn] and in one case [Zn]----CTV, were found to be the most probable geometry to promote host–guest associations in these systems.

The 3D [(Cu₂Br₂){μ-EtS(CH₂)₄SEt}]_n material: a rare example of a coordination polymer exhibiting triplet–triplet annihilation. Antoine Bonnot, Paul-Ludovic Karsenti, Frank Juvenal, Christopher Golz, Carsten Strohmann, Daniel J. Fortin, Michael Knorr, and Pierre D. Harvey. Physical Chemistry Chemical Physics, 2016, 18, 24845-24849. https://doi.org/10.1039/C6CP04728A

Abstract: EtS(CH₂)₄SEt, L1, forms with CuI a luminescent 2D polymer [Cu₄I₄{μ-L1}₂]_n (CP1), which exhibits no triplet excitation energy migration, but with CuBr, it forms a 3D material (CP2), [(Cu₂Br₂){μ-L1}]_n consisting of parallel (Cu₂Br₂S₂)_n layers bridged by L1's. CP2 shows T₁–T₁ annihilation at 298 K but not at 77 K.

Pentacene- and BODIPY-Containing trans-Bis(ethynyl)bis(phosphine)platinum(II) Organometallic Polymers: A DFT Point of View. Antoine Bonnot and Pierre D. Harvey. Journal of Inorganic and Organometallic Polymers and Materials, 2016, 26, 1328-1337. https://doi.org/10.1007/s10904-016-0405-8

Abstract: The effect of the polymer dimension and the nature of the end-group of oligomer models containing pentacence ([pen]) and BODIPY ([BOD]) alternating with the organometallic fragment trans-bis(trialkylphosphine)platinum(II) ([Pt]), i.e. ([Ar]_n–[Pt]_m)_x with [Ar] = C≡C–[pen]–C≡C, C≡C–[BOD]–C≡C, and 1 < x < 4, on their structures and optical properties were investigated by means of DFT and TDDFT (B3LYP) calculations. For sake of reduction of computation size for the oligomers, the trialkylphosphine was set to PMe₃ instead of the commonly encountered PBu₃ in the experimental articles. Two specific aspects were addressed. Firstly, a series of computations were performed in a systematic manner in order to find the best conditions for these calculations (namely the choice of basis sets and solvent fields), due to the large size of the oligomer models. Secondly, the effect of the oligomer size and nature of the terminal unit of ([Ar]_n–[Pt]_m)_x, namely C≡C–[pen]–C≡CH or C≡C–[BOD]–C≡CH and [Pt]–Cl, on the structure and electronic properties have also been examined. These calculations indicate that the nature of end-groups has a little impact on the properties mentioned above for the alternating ((C≡C–[BOD]–C≡C)_n–[Pt]_m)_x oligomers, but some minor effects are noted for the (C≡C–[pen]–C≡C)-containing species. Noteworthy, the evolution of the properties, notably the position of the lowest energy electronic transition, shows no significant evolution above 3 units. This computational result indicates the limitation of the electronic communication across the polymer chains. The lowest energy electronic states are all mainly ππ* located in the [Ar] fragment. Consequently, this work was limited to 4 units only.

Can a highly flexible copper(i) cluster-containing 1D and 2D coordination polymers exhibit MOF-like properties? Antoine Bonnot, Frank Juvenal, Anthony Lapprand, Daniel J. Fortin, Michael Knorr, and Pierre D. Harvey. Dalton Transactions, 2016, 45, 11413-11421. https://doi.org/10.1039/C6DT01375A

Abstract: The reaction of CuI with the highly flexible dithioether ligand p-TolS(CH₂)₈STol-p affords both in MeCN or in EtCN the 2D coordination polymers [Cu₈I₈{p-TolS(CH₂)₈STol-p}₃(solvent)₂]_n (1·MeCN and 1·EtCN) containing octanuclear Cu₈I₈ clusters as connection nodes. In contrast, treatment of CuI with p-tBuC₆H₄S(CH₂)₈SC₆H₄But-p in EtCN solution leads to the formation of the luminescent 1D CP [Cu₄I₄{tBuC₆H₄S(CH₂)₈SC₆H₄-tBu}₂(EtCN)₂]_n (2·EtCN) incorporating Cu₄(μ₃-I)₄ clusters of the closed cubane type as secondary building units (SBUs). The 2D coordination polymers 1·MeCN and 1·EtCN demonstrate the ability to lose their solvent crystallisation molecules under vacuum and readsorb the same or a new one using vapor as monitored by powder X-ray diffraction, thermogravimetric, IR, chromaticity, emission spectra and emission lifetime measurements. Conversely, the 1D material 2·EtCN does not readsorb EtCN, likely due to the collapse of the macrocycles formed by the metal cluster nodes and flexible long-chained ArSC8SAr ligands but absorbs a smaller substrate such as CO₂.

Platinum(ii) cyclometallates featuring broad emission bands and their applications in color-tunable OLEDs and high color-rendering WOLEDs. Guiping Tan, Shuming Chen, Chi-Ho Siu, Adam Langlois, Yongfy Qiu, Hongbo Fan, Cheuk-Lam Ho, Pierre D. Harvey, Yih Hsing Lo, Li Liu, and Wai-Yeung Wong. Journal of Materials Chemistry C, 2016, 4, 6016-6026. https://doi.org/10.1039/C6TC01594H

Abstract: Two phosphorescent platinum(II) cyclometallated complexes with phenoxy groups (1 and 2) have been developed. The modified organic ligands derived by combining the phenoxy moiety and 2-phenylpyridine conferred them with a more flexible structure, leading to superior intermolecular interaction properties of the resulting Pt(II) metallophosphors. Because of the excimer formation induced by Pt(II) complexes 1 and 2, the emission color can be tuned over a wide range from cyan to orange by simply increasing the concentration of the Pt(II) metallophosphors. Inspired by their broad emission band, color tunability and outstanding electroluminescence (EL) performance, these two Pt(II) phosphors complemented with blue fluorescent emitter 4,4′-bis(9-ethyl-3-carbazovinylene)-1,1′-biphenyl (BCzVBi) were employed in manufacturing high color-rendering white organic light-emitting devices (WOLEDs). In such simple two-emitter systems, 1-based WOLEDs exhibited reasonable EL performance with an external quantum efficiency (η_ext) of 11.7%, luminance efficiency (η_L) of 29.1 cd A⁻¹, power efficiency (η_p) of 16.9 lm W⁻¹ and color rendering index (CRI) of 77, whereas 2-based WOLEDs demonstrated an η_ext of 10%, η_L of 21.7 cd A⁻¹, η_p of 10.7 lm W⁻¹ and CRI of 88.

Designs of 3-Dimensional Networks and MOFs Using Mono- and Polymetallic Copper(I) Secondary Building Units and Mono- and Polythioethers: Materials Based on the Cu–S Coordination Bond. Pierre D. Harvey and Michael Knorr. Journal of Inorganic and Organometallic Polmers and Materials, 2016, 26, 1174-1197. https://doi.org/10.1007/s10904-016-0378-7

Abstract: This mini-review surveys 23 structures of 3D coordination polymers built upon mono-, di- as well as cyclic and acylic polythioethers. An emphasis is put on the Secondary Building Units (SBU) and the physical properties. Importantly, the key feature is that the dominant SBU is not the rhomboid (Cu₂X₂S₄), but an inorganic polymer containing at least the chain of the type (CuX)_n. In the latter type of SBU, these chain formations are observed for X = I, but predominantly for X = CN. In addition, a large portion of the surveyed materials exhibit rich photophysical properties, but on several occasions, these materials exhibit properties often attributed to MOFs, mainly solvent exchange.

Metal Linkage Effects on Ultrafast Energy Transfer. Hervé Dekkiche, Antoine Buisson, Adam Langlois, Paul-Ludovic Karsenti, Laurent Ruhlmann, Romain Ruppert, and Pierre D. Harvey. Chemistry - a European Journal, 2016, 22(30), 10484-10493. https://doi.org/10.1002/chem.201601322

Abstract: We report the preparation of several new porphyrin homodimers bridged by a platinum(II) ion in which very intense electronic communication through the coordination link occurs. Moreover, the synthesis of a new porphyrin dyad and its photophysical properties are reported. This dyad exhibits the fastest singlet energy transfer ever reported for synthetic systems between a zinc(II) porphyrin and a porphyrin free base. This extremely fast transfer (∼100 femtoseconds) is in the same range as the fastest one measured in natural systems. This feature is due to the platinum(II) linker, which allows for strong MO couplings between the two porphyrin units as experimentally supported by electrochemistry and corroborated by DFT computations.

Triplet Energy Transfers in Well-Defined Host–Guest Porphyrin–Carboxylate/Cluster Assemblies. Peng Luo, Paul-Ludovic Karsenti, Benoit Marsan, and Pierre D. Harvey. Inorganic Chemistry, 2016, 55(9), 4410-4420. https://doi.org/10.1021/acs.inorgchem.6b00185

Abstract: The dyes (5-(4-carboxylphenyl)-10,15,20-tritolylporphyrinato)zinc(II) (MCP) and (5,15-bis(4-carboxylphenyl)-15,20-ditolylporphyrinato)zinc(II) (DCP), as their sodium salts, were used to form assemblies with the unsaturated cluster Pd₃(dppm)₃(CO)²⁺ ([Pd₃²⁺], dppm = (Ph₂P)₂CH₂) via ionic CO₂^–···Pd₃²⁺ interactions. The photophysical properties in their triplet states were studied. The position of the T₁ state of [Pd₃²⁺] (∼8190 cm^–1) has been proposed using DFT computations and was corroborated by the presence of a T_n → S₀ delayed emission at 680–700 nm arising from a T₁–T₁ annihilation process at 77 K. The static quenching of the near-IR phosphorescence of the dyes at 785 nm (T₁ → S₀) was observed. Thermodynamically poor reductive and oxidative driving forces render the photoinduced electron transfer quenching process either inoperative or very slow in the T₁ states. Instead, slow to medium T₁–T₁ energy transfer (³dye*···[Pd₃²⁺] → dye···³[Pd₃²⁺]*) operates through a Förster mechanism exclusively with k_ET values of ∼1 × 10⁵ s^–1 on the basis of transient absorption measurements at 298 K.

The first example of cofacial bis(dipyrrins). Jude Deschamps, Yi Chang, Adam Langlois, Nicolas Desbois, Claude P. Gros, and Pierre D. Harvey. New Journal of Chemistry, 2016, 40, 5835-5845. https://doi.org/10.1039/C5NJ03347K

Abstract: Two series of cofacial bis(dipyrrins) were prepared and their photophysical properties as well as their bimolecular fluorescence quenching with C₆₀ were investigated. DFT and TDDFT computations were also performed as a modeling tool to address the nature of the fluorescence state and the possible inter-chromophore interactions. Clearly, there is no evidence for such interactions and the bimolecular quenching of fluorescence, in comparison with mono-dipyrrins, indicates that C₆₀-bis(dipyrrin) contacts occur from the outside of the “mouth” of the cofacial structure.

Ultrafast Electron Transfers in Organometallic Supramolecular Assemblies Built with a NIR-Fluorescent Tetrabenzoporphyrine Dye and the Unsaturated Cluster Pd₃(dppm)₃(CO)²⁺. Peng Luo, Paul-Ludovic Karsenti, Gessie Brisard, Benoit Marsan, and Pierre D. Harvey. Organometallics, 2016, 35(5), 816-826. https://doi.org/10.1021/acs.organomet.6b00050

Abstract: The sodium 9,18,27,36-tetra-(4-carboxyphenylethynyl)tetrabenzoporphyrinatozinc(II) (TCPEBP) and sodium 5,10,15,20-tetra-(4-carboxyphenylethynyl)porphyrinatozinc(II) (TCPEP, for comparison purposes) salts were prepared to investigate the ionic driven host–guest assemblies made with the unsaturated redox-active cluster Pd₃(dppm)₃(CO)²⁺ ([Pd₃²⁺], dppm = Ph₂PCH₂PPh₂ as a PF₆^– salt). Nonemissive dye···[Pd₃²⁺]_x assemblies (x = 1–4) are formed in methanol with K_1x (binding constants) values of 83 200 (TCPEBP) and 70 400 M^–1 (TCPEP; average values extracted from graphical methods (Benesi–Hildebrand, Scott, and Scatchard), matching those obtained from fluorescence quenching experiments (static model)). These values are consistent with the more electron rich TCPEBP dye. This conclusion is corroborated by electrochemical data, which indicate a lower oxidation potential of the TCPEBP dye (+0.46 V) vs TCPEP (+0.70 V vs SCE) and by shorter calculated average Pd···O distances (DFT (B3LYP): 3.259 vs 3.438 Å, respectively). Using the position of the 0–0 component of the Q-bands and the electrochemical data, the excited-state driving forces for dye*···[Pd₃²⁺]_x → dye^+•···[Pd₃^+•][Pd₃²⁺]_x–1 are estimated for TCPEBP (+1.22 V vs SCE) and TCPEP (1.08 V vs SCE). The time scale for this process occurs within the laser pulse (fwhm <75–110 fs) during the measurements of the femtosecond transient absorption spectra. Conversely, the back electron transfers (dye^+•···[Pd₃^+•][Pd₃²⁺]_x–1 → dye···[Pd₃²⁺]_x) occur well within 1 ps (respectively 650 and 170 fs for TCPEBP and TCPEP). Arguments are provided that the reorganization energy governs this difference.

Synthesis, Characterization, and Electronic Properties of Porphyrins Conjugated with N-Heterocyclic Carbene (NHC)–Gold(I) Complexes. Jean-François Longevial, Adam Langlois, Antoine Buisson, Charles H. Devillers, Sébastien Clément, Arie van der Lee, Pierre D. Harvey, and Sébastien Richeter. Organometallics, 2016, 35(5), 663-672. https://doi.org/10.1021/acs.organomet.5b00966

Abstract: Porphyrins fused to peripheral N-heterocyclic carbenes (NHC) across two neighboring β,β-pyrrolic positions were used for the synthesis of different mono- and bis-carbenic gold(I) complexes. These studies also revealed how it is possible to modulate the reactivity of the peripheral NHC by deprotonating the inner NH groups of the fused free base porphyrin core. All complexes were fully characterized and displayed high stability, allowing the formation of mono-carbenic and also stable homoleptic and heteroleptic bis-carbenic Au(I) complexes. Optical and electrochemical properties of bis-carbenic Au(I) revealed no or weak electronic communication between the porphyrins, which behave as two independent groups.

Electron-Transfer Kinetics within Supramolecular Assemblies of Donor Tetrapyrrolytic Dyes and an Acceptor Palladium Cluster. Peng Luo, Paul-Ludovic Karsenti, Gessie Brisard, Benoit Marsan, and Pierre D. Harvey. Inorganic Chemistry, 2016, 55(4), 1894-1904. https://doi.org/10.1021/acs.inorgchem.5b02788

Abstract: 9,18,27,36-Tetrakis[meso-(4-carboxyphenyl)]tetrabenzoporphyrinatozinc(II) (TCPBP, as a sodium salt) was prepared in order to compare its photoinduced electron-transfer behavior toward unsaturated cluster Pd₃(dppm)₃(CO)²⁺ ([Pd₃²⁺]; dppm = Ph₂PCH₂PPh₂ as a PF₆^– salt) with that of 5,10,15,20-tetrakis[meso-(4-carboxyphenyl)]porphyrinatozinc(II) (TCPP) in nonluminescent assemblies of the type dye···[Pd₃²⁺]_x (x = 0–4; dye = TCPP and TCPBP) using femtosecond transient absorption spectroscopy. Binding constants extracted from UV–vis titration methods are the same as those extracted from fluorescence quenching measurements (static model), and both indicate that the TCPBP···[Pd₃²⁺]_x assemblies (K₁₄ = 36000 M^–1) are slightly more stable than those for TCPP···[Pd₃²⁺]_x (K₁₄ = 27000 M^–1). Density functional theory computations (B3LYP) corroborate this finding because the average ionic Pd···O distance is shorter in the TCPBP···[Pd₃²⁺] assembly compared to that for TCPP···[Pd₃²⁺]. Despite the difference in the binding constants and excited-state driving forces for the photoinduced electron transfer in dye*···[Pd₃²⁺] → dye^•+···[Pd₃^•+], the time scale for this process is ultrafast in both cases (<85 fs). The time scales for the back electron transfers (dye^•+···[Pd₃^•+] → dye···[Pd₃²⁺]) occurring in the various observed species (dye···[Pd₃²⁺]_x; x = 0–4) are the same for both series of assemblies. It is concluded that the structural modification on going from porphyrin to tetrabenzoporphyrin does not greatly affect the kinetic behavior in these processes.

1,4-Bis(arylthio)but-2-enes as Assembling Ligands for (Cu₂X₂)_n (X = I, Br; n = 1, 2) Coordination Polymers: Aryl Substitution, Olefin Configuration, and Halide Effects on the Dimensionality, Cluster Size, and Luminescence Properties. Antoine Bonnot, Michael Knorr, Fabrice Guyon, Marek M. Kubicki, Yoann Rousselin, Carsten Strohmann, Daniel J. Fortin, and Pierre D. Harvey. Crystal Growth and Design, 2016, 16(2), 774-788. https://doi.org/10.1021/acs.cgd.5b01360

Abstract: CuI reacts with E-PhS(CH₂CH═CHCH₂)SPh, L1, to afford the coordination polymer (CP) [Cu₂I₂{μ-E-PhS(CH₂CH═CHCH₂)SPh}₂]_n (1a). The unprecedented square-grid network of 1 is built upon alternating two-dimensional (2D) layers with an ABAB sequence and contains rhomboid Cu₂(μ₂-I)₂ clusters as secondary building units (SBUs). Notably, layer A, interconnected by bridging L1 ligands, contains exclusively dinuclear units with short Cu···Cu separations [2.6485(7) Å; 115 K]. In contrast, layer B exhibits Cu···Cu distances of 2.8133(8) Å. The same network is observed when CuBr reacts with L1. In the 2D network of [Cu₂Br₂{μ-E-PhS(CH₂CH═CHCH₂)SPh}₂]_n (1b), isotype to 1a, one square-grid-type layer contains Cu₂(μ₂-Br)₂ SBUs with short Cu···Cu contacts [2.7422(6) Å at 115K], whereas the next layer incorporates exclusively Cu₂(μ₂-Br)₂ SBUs with a significantly longer Cu···Cu separation [2.9008(10) Å]. The evolution of the crystallographic parameters of 1a and 1b was monitored between 115 and 275 K. Conversely, the isomeric Z-PhS(CH₂CH═CHCH₂)SPh ligand L2 reacts with CuI to form the 2D CP [Cu₄(μ₃-I)₄(μ-Z-PhS(CH₂CH═CHCH₂)SPh}₂]_n (2a) with closed-cubane SBUs. A dinuclear zero-dimensional complex [Cu₂Br₂{μ-Z-PhS(CH₂CH═CHCH₂)SPh}₂] (2b) is formed when CuBr is reacted with L2. Upon reaction of E-TolS(CH₂CH═CHCH₂)STol, L3, with CuI, the 2D CP [{Cu(μ₃-I)}₂(μ-L3)]_n containing parallel-arranged infinite inorganic staircase ribbons, is generated. When CuX reacts with Z-TolS(CH₂CH═CHCH₂)STol, L4, the isostructural 2D CPs [Cu₂X₂{μ-Z-TolS(CH₂CH═CHCH₂)STol}₂] (4a X = I; 4b X = Br) are formed. In contrast to the CPs 1a,b, the layers based on rhombic grids of 4a,b incorporate Cu₂(μ₂-X)₂ SBUs featuring uniformly identical Cu···Cu distances within each layer. The TGA traces showed that all these materials are stable up to ∼200 °C. Moreover, the photophysical properties have been studied, including absorption, emission, excitation spectra, and emission lifetimes at 298 and 77 K. The spectra were interpreted using density functional theory (DFT) and time-dependent DFT calculations.

Are the orientation and bond strength of the RCO₂⁻⋯M link key factors for ultrafast electron transfers? Peng Luo, Paul-Ludovic Karsenti, Gessie Brisard, Benoit Marsan, and Pierre D. Harvey. Chemical Communications, 2015, 51, 17305-17308. https://doi.org/10.1039/C5CC06779K

Abstract: The photo-induced electron transfers in the “straight up” ionic assemblies [Pd₃²⁺]⋯MCP and [Pd₃²⁺]⋯DCP⋯[Pd₃²⁺] ([Pd₃²⁺]* → MCP or DCP) are ultrafast (<85 fs) indicating that it is not necessary to have a strong coordination bond or a bent geometry to obtain fast electron injection in porphyrin-containing DSSCs.

Push–Pull Porphyrin-Containing Polymers: Materials Exhibiting Ultrafast Near-IR Photophysics. Xiaorong Wang, Gessie Brisard, Daniel J. Fortin, Paul-Ludovic Karsenti, and Pierre D. Harvey. Macromolecules, 2015, 48(19), 7024-7038. https://doi.org/10.1021/acs.macromol.5b01607

Abstract: Four push–pull polymers of structure (C≡C–[Zn]–C≡C–A)_n (A = isoindigo (P1), bis(α-methylamino-1,4-benzene)quinone (P2), 2-(N-methylamino-1,4-benzene)-N-1,4-benzene-maleimide (P3), and 2,2′-anthraquinone (P4); [Zn] = [bis(meso-aryl)porphyrin]zinc(II) = donor) and models M1 and M2 (A′–C≡C–[Zn]–C≡C–A′; A′ = respectively naphtoquinone and 2-anthraquinone) were prepared and characterized (¹H and ¹³C NMR, elemental analysis, GPC, TGA, cyclic voltammetry, steady state and ultrafast time-resolved UV–vis and emission spectroscopy) and studied by density functional theory (DFT) and time-dependent DFT (TDDFT) in order to address the nature of the low-lying singlet and triplet excited states. P1 (fully conjugated polymer), P2 (formally nonconjugated but exhibit strong electronic communication accross the chain) and P4 (formally nonconjugated but local conjugation between the donor and acceptor) are near-IR emitters (λ_max > 750 nm). M1 and M2 are mono-C≡C–[Zn]–C≡C species, and P3 exhibits a very modest CT contribution (as maleimide is a weak acceptor) and are not near-IR emitters. The nature of the S₁ and T₁ excited states are CT processes donor* → acceptor. In P1–P4, a dual fluorescence (7.7 < τ_F < 770 ps; except one value at 2.5 ns; P3) is depicted, which are assigned to fluorescences arising from the terminal and central units of the polymers identified from the comparison with M1 and M2. The high and low energy fluorescences are respectively short (77 < τ_F < 166 ps) and long-lived (688 < τ_F < 765 ps) suggesting S₁ energy transfers with rates, k_ET, of 7.1 (P1), 12 (P2) and 4.5 (ns)⁻¹ (P4). The fs transient absorption spectra exhibit particularly very short triplet lifetimes (2.3 < τ_T1 < 87 ns) explaining the absence of phosphorescence. Also ultrafast lifetimes (85 < τ < 1290 fs) for species excited in the 0–0 peak of the Q-band (650 nm; i.e., ππ* porphyrin level) indicating its rather efficient nonradiative deactivation (S_n ∼ > S₁ and S_n ∼ > T_m). When cooling takes place or the solution concentration is increased, new red-shifted fluorescence bands appear, evidencing aggregate formation. Both fluorescence and transient absorption lifetimes of P1–P4 become shorter and their band intensity lower. Finally, the position of the optically silent phosphorescence has been predicted to be in the 1300 (P1, P2) and 1000 nm (P3, P4) zones (DFT).

Modular P-Chirogenic Phosphine-Sulfide Ligands: Clear Evidence for Both Electronic Effect and P-Chirality Driving Enantioselectivity in Palladium-Catalyzed Allylations. Jérôme Bayardon, Milène Maronnat, Adam Langlois, Yoann Rousselin, Pierre D. Harvey, Sylvain Jugé. Organometallics, 2015, 34(17), 4340-4358. https://doi.org/10.1021/acs.organomet.5b00585

Abstract: Using the ephedrine methodology, modular stereoselective syntheses of a new class of P-chirogenic phosphines bearing a sulfur-chelating arm (P*,S-hybrid ligand) are described. A first series of syntheses based on a Fries-like rearrangement of P-chirogenic phosphinite-boranes, which are prepared from 2-bromobenzyl or 2-bromophenethyl alcohol and are mediated by metal–halide exchange, have been performed. This rearrangement affords phosphine-boranes stereospecifically with an o-hydroxyalkylphenyl substituent. The latter residue is subsequently converted into a sulfur-containing group. In a second series, the stereoselective syntheses were achieved according to a new strategy involving a reaction of a thiophenyllithium reagent with a P-chirogenic phosphinite. The X-ray structures of the P*,S ligands and their palladium complexes allow us to address the absolute configuration at both the phosphorus and sulfur centers. The P*,S ligands were used in palladium-catalyzed allylic alkylations, as tests, affording asymmetric inductions up to 96% ee. Computer modeling corroborates the regio- and enantioselectivity of the Pd-catalyzed allylations and the low influence of the substituent carried by the sulfur moiety, particularly when the chelate forms a six-membered ring with the metal.

Profound Substituent Effect on the Structural, Optical, Photophysical, and Electrochemical Properties of N,N′-Anthraquinone Diimine-Containing Platinum–Organometallic Polymers. Xiaorong Wang, Tommy Kenny, Daniel J. Fortin, Sawkat M. Aly, Gessie Brisard, and Pierre D. Harvey. Organometallics, 2015, 34(8), 1567-1581. https://doi.org/10.1021/acs.organomet.5b00154

Abstract: A series of conjugated organometallic-substituted derivatives of anthraquinone diimine-(trans-diethynylbis(tri-n-butylphosphine)platinum(II)-containing polymers along with the corresponding mixed-valence analogues bis(4-phenylamino)anthracene and anthraquinone diimine and model compounds (substituent = H, Br, 2Br, NH₂, 2NH₂) were investigated by electrochemistry, UV–visible and emission spectroscopy, photophysics, and DFT and TDDFT computations, as a means to shine light on the electronic communication across the chain of the seemingly unconjugated polyaniline in its emeraldine form and to examine the substituent effect.

Reactivity of CuI and CuBr toward Dialkyl Sulfides RSR: From Discrete Molecular Cu₄I₄S₄ and Cu₈I₈S₆ Clusters to Luminescent Copper(I) Coordination Polymers. Michael Knorr, Antoine Bonnot, Antony Lapprand, Abderrahim Khatyr, Carsten Strohmann, Marek M. Kubicki, Yoann Rousselin, and Pierre D. Harvey. Inorganic Chemistry, 2015, 54(8), 4076-4093. https://doi.org/10.1021/acs.inorgchem.5b00327

Abstract: The 1D coordination polymer (CP) [(Me₂S)₃{Cu₂(μ-I)₂}]_n (1) is formed when CuI reacts with SMe₂ in n-heptane, whereas in acetonitrile (MeCN), the reaction forms exclusively the 2D CP [(Me₂S)₃{Cu₄(μ-I)₄}]_n (2) containing “flower-basket” Cu₄I₄ units. The reaction product of CuI with MeSEt is also solvent-dependent, where the 1D polymer [(MeSEt)₂{Cu₄(μ₃-I)₂(μ₂-I)₂}(MeCN)₂]_n (3) containing “stepped-cubane” Cu₄I₄ units is isolated in MeCN. In contrast, the reaction in n-heptane affords the 1D CP [(MeSEt)₃{Cu₄(μ₃-I)₄}]_n (4) containing “closed-cubane” Cu₄I₄ clusters. The reaction of MeSPr with CuI provides the structurally related 1D CP [(MeSPr)₃{Cu₄(μ₃-I)₄}]_n (5), for which the X-ray structure has been determined at 115, 155, 195, 235, and 275 K, addressing the evolution of the metric parameters. Similarly to 4 and the previously reported CP [(Et₂S)₃{Cu₄(μ₃-I)₄}]_n (Inorg. Chem.2010, 49, 5834), the 1D chain is built upon closed cubanes Cu₄(μ₃-I)₄ as secondary building units (SBUs) interconnected via μ-MeSPr ligands. The 0D tetranuclear clusters [(L)₄{Cu₄(μ₃-I)₄}] [L = EtSPr (6), Pr₂S (7)] respectively result from the reaction of CuI with EtSPr and n-Pr₂S. With i-Pr₂S, the octanuclear cluster [(i-Pr₂S)₆{Cu₈(μ₃-I)₃}(μ₄-I)₂}] (8) is formed. An X-ray study has also been performed at five different temperatures for the 2D polymer [(Cu₃Br₃)(MeSEt)₃]_n (9) formed from the reaction between CuBr and MeSEt in heptane. The unprecedented framework of 9 consists of layers with alternating Cu(μ₂-Br)₂Cu rhomboids, which are connected through two μ-MeSEt ligands to tetranuclear open-cubane Cu₄Br₄ SBUs. MeSPr forms with CuBr in heptane the 1D CP [(Cu₃Br₃)(MeSPr)₃]_n (10), which is converted to a 2D metal–organic framework [(Cu₅Br₅)(μ₂-MeSPr)₃]_n (11) incorporating pentanuclear [(Cu₅(μ₄-Br)(μ₂-Br)] SBUs when recrystallized in MeCN. The thermal stability and photophysical properties of these materials are also reported.

Ruthenium and Osmium Complexes of Phosphine-Porphyrin Derivatives as Potential Bimetallic Theranostics: Photophysical Studies. Pierre D. Harvey, Semra Tasan, Claude P. Gros, Charles H. Devillers, Philippe Richard, Pierre Le Gendre, and Ewen Bodio. Organometallics, 2015, 34(7), 1218-1227. https://doi.org/10.1021/om5011808

Abstract: A series of (η⁶-p-cymene)ruthenium(II)- and osmium(II) complexes of porphyrin-phosphane derivatives have been synthesized as potential bimetallic theranostic candidates. The photophysical and electrochemical properties were investigated, and these species desirably exhibit no or almost no photoinduced intramolecular atom, energy, and electron transfer between the dye and the metallic fragment. These favorable features are mostly associated with the presence of their long chain (i.e., ∼ 1 nm) separating the two functional units. Interestingly, a decrease in emission intensity and lifetimes (up to 35-fold) has been observed, which was ascribed to a small heavy atom effect. This effect is possible as a chain folding driven by an intramolecular H-bond (N–H···Cl–M).

CuX (X = Cl, Br, I) Containing Coordination Polymers Built Upon Isomeric RSCH₂C≡CCH₂SR (R = p-Tolyl, Benzyl) Dithioether Ligands: First Example of a Luminescent (CuCl)_n/Dithioether Network. Antoine Bonnot, Michael Knorr, Carsten Strohomann, Christopher Golz, Daniel J. Fortin, Pierre D. Harvey. Journal of Inorganic and Organometallic Polymers and Materials, 2015, 25, 480-494. https://doi.org/10.1007/s10904-015-0204-7

Abstract: The CuBr salt reacts with the acetylenic dithioether 1,4-bis(p-tolylthio)but-2-yne (L1) to generate the 1D [{Cu(μ₂-Br)₂Cu}(μ-p-MeC₆H₄SCH₂C≡CCH₂SC₆H₄Me-p)₂]_ncoordination polymer (1), contrasting with the previously reported reaction with CuI, which provided a 2D network [{Cu₄(μ₃-I)₄}(μ-p-MeC₆H₄SCH₂C≡CCH₂SC₆H₄Me-p)₂]_n. (JIOPM, 2014, 24, 190-200). The ribbons of 1 incorporate two different types of alternating centrosymmetric Cu(μ₂-Br)₂Cu rhomboids displaying loose Cu···Cu contacts of 2.9306(14) and 2.9662(14) Å. The reaction of CuI and CuBr with the isomeric dithioether ligand 1,4-bis(benzylthio)but-2-yne (L2) yields the isomorphous dinuclear 0D complexes [{Cu(μ₂-X)₂Cu}(μ-PhCH₂SCH₂C≡CCH₂SCH₂Ph)₂] (2a: X = I; 2b: X = Br). These species represent the first examples of dinuclear [S₂{Cu(μ₂-X)₂Cu}S₂] complexes spanned by a dithioether ligand. In contrast, treatment of CuCl with L2 gives rise to the formation of an unusual 2D coordination polymer [{Cu₂(μ₂-Cl)(μ₃-Cl)}(μ-PhCH₂SCH₂C≡CCH₂SCH₂Ph)]_n(3), in which the layers are assembled both by dative Cu–S thioether bonds and organometallic Cu-π-acetylenic interactions via the triple bond of the L2 ligand. Furthermore, the Cu(I) centers are interconnected through μ₂- and μ₃-bound chloro ligands. Finally, thermal stability and photophysical proprieties were studied. This investigation demonstrated the interesting luminescent behavior of CuCl-containing coordination polymer (3).

Very fast singlet and triplet energy transfers in a tri-chromophoric porphyrin dyad aided by the truxene platform. Adam Langlois, Hai-Jun Xu, Paul-Ludovic Karsenti, Claude P. Gros, and Pierre D. Harvey. Journal of Porphyrins and Phthalocyanines, 2015, 19(01-03), 427-441. https://doi.org/10.1142/S1088424615500327

Abstract: A trichromophoric dyad composed of an octa-β-alkyl-palladium(II)porphyrin (donor) and two tri-meso-aryl-zinc(II)porphyrins (acceptors) held by a truxene spacer exhibits very fast rates for triplet energy transfers at 77 (k_ET(T₁) = 1.63 × 10⁸ s^-1) and 298 K (k_ET(T₁) = 3.44 × 10⁸ s^-1), whereas the corresponding singlet energy transfer rates, k_ET(S₁) = 3.9 × 10¹⁰ s^-1 (77 K) and k_ET(S₁) = 6.0 × 10¹⁰ s^-1 (298 K), are also considered fast. The interpretation for these results is that the energy transfer processes proceed via a through bond Dexter mechanism (i.e. double electron exchange) supported by comparison with literature data and evidence for a moderate MO coupling between the donor and acceptor chromophores in the frontier MOs.

Stabilization of (CuX)_nClusters (X = Cl, Br, I; n = 2, 4, 5, 6, 8) in Mono- and Dithioether-Containing Layered Coordination Polymers. Pierre D. Harvey and Michael Knorr. Journal of Cluster Science, 2015, 26, 411-459. https://doi.org/10.1007/s10876-014-0831-0

Abstract: More than 50 of layered (i.e., 2D) coordination polymers containing (CuX)_nclusters (X = Cl, Br, I; n = 2, 4, 5, 6, and 8) as secondary building units (SBUs) and mono- and dithioether as assembling ligands are described. This mini-review is separated into two categories; mono- (10) and dithioether (45 polymers), devoted on 2D networks. Within these 55 2D structures visited, the occurrence of the SBU motifs (CuX)_nwhere n = 2, 4, 5, 6, and 8 are dominated by the rhomboids (Cu₂X₂S_x; 30) and the closed and open cubanes (Cu₄I₄S₄; 16). Only 10 different other SBU motifs are found in these 2D materials (note that one polymer shares two different motifs). Some emission properties are also provided. Generally, closed cubane cluster-containing coordination polymers exhibit more intense emissions than the rhomboid dimers, which are very weakly or non-emissive.

Coordination RC₆H₄S(CH₂)₈SC₆H₄R/(CuI)_n Polymers (R (n) = H (4); Me (8)): An Innocent Methyl Group that Makes the Difference. Pierre D. Harvey, Antoine Bonnot, Antony Lapprand, Carsten Strohmann, and Michael Knorr. Macromolecular Rapid Communications, 2015, 36(7), 654-659. https://doi.org/10.1002/marc.201400659

Abstract: Under identical conditions, CuI reacts with PhS(CH₂)₈SPh and p-TolS(CH₂)₈STol-p affording, respectively, a luminescent 1D coordination polymer [Cu₄I₄{μ₂-PhS(CH₂)₈SPh}₂]_n (1) and an unprecedented 2D network [Cu₈I₈{μ₂-p-TolS(CH₂)₈STol-p}₃(MeCN)₂]_n (2), which incorporate closed-cubane Cu₄I₄ and octanuclear Cu₈I₈ clusters of as connecting nodes. Their thermal and photophysical properties exhibit notable differences.

Gold–phosphine–porphyrin as potential metal-based theranostics. Semra Tasan, Cynthia Licona, Pierre-Emmanuel Doulain, Clément Michelin, Claude P. Gros, Pierre Le Gendre, Pierre D. Harvey, Catherine Paul, Christian Gaiddon, and Ewen Bodio. Journal of Biological Inorganic Chemistry, 2015, 20, 143-154. https://doi.org/10.1007/s00775-014-1220-8

Abstract: Two new gold-phosphine-porphyrin derivatives were synthesized and fully characterized, and their photophysical properties investigated along a water-soluble analog. The cytotoxicity of the compounds was tested on cancer cells (HCT116 and SW480), and their cell uptake was followed by fluorescence microscopy in vitro (on SW480). The proof that the water-soluble gold-phosphine-porphyrin is a biologically active compound that can be tracked in vitro was clearly established, especially concerning the water-soluble analog. Some preliminary photodynamic therapy (PDT) experiments were also performed. They highlight a dramatic increase of the cytotoxicity when the cells were illuminated for 30 min with white light.

Phosphorescent Cu(i) complexes based on bis(pyrazol-1-yl-methyl)-pyridine derivatives for organic light-emitting diodes. Fengshou Wu, Jie Li, Hongbo Tong, Zaoying Li, Chihaya Adachi, Adam Langlois, Pierre D. Harvey, Li Liu, Wai-Yeung Wong, Wai-Kwok Wong, and Xunjin Zhu. Journal of Materials Chemistry C, 2015, 3, 138-146. https://doi.org/10.1039/C4TC01885K

Abstract: Mononuclear Cu(I) complexes based on bis(pyrazol-1-yl-methyl)-pyridine derivatives and ancillary triphenylphosphine have been prepared and characterized by ¹H NMR, mass spectroscopy and single-crystal X-ray analysis. The thermogravimetric analysis shows that the complexes exhibit high thermal stability. The electronic absorption spectra display two features in the regions of 230–260 and 290–350 nm attributable to mixed ligand-to-ligand (LLCT) and metal-to-ligand-charge-transfer (MLCT) excited states, which is supported by the results of density functional theory (DFT) and time-dependent DFT (TDDFT) calculations on these Cu(I) complexes. These complexes are strongly emissive in the solid state at ambient temperature. Intense blue or green emission in the poly(methyl methacrylate) film is observed in the region of 475–518 nm for these complexes with the emission lifetimes in the microsecond time scale (12–20 μs), indicating that the emission may be phosphorescence emission. Increasing the steric hindrance of the substituents on the pyrazole unit results in a blue-shift of the emission bands and enhanced emission quantum efficiency in PMMA films. The two most emissive complexes have been used for the fabrication of phosphorescent organic light-emitting diodes (POLEDs).

Strategic Modulation of the Photonic Properties of Conjugated Organometallic Pt–Ir Polymers Exhibiting Hybrid CT-Excited States. Ahmen M. Soliman, Eli Zysman-Colman, and Pierre D. Harvey. Macromolecular Rapid Communications, 2015, 36(7), 627-632. https://doi.org/10.1002/marc.201400542 

Abstract: Polymer 6, ([trans-Pt(PBu₃)₂(CC)₂]-[Ir(dFMeppy)₂(N^N)](PF₆))_n, (([Pt]-[Ir](PF₆))_n; N^N = 5,5′-disubstituted-2,2′-bipyridyl; dFMeppy = 2-(2,4-difluoro-phenyl)-5-methylpyridine) is prepared along with model compounds. These complexes are investigated by absorption and emission spectroscopy and their photophysical and electrochemical properties are measured and compared with their corresponding non fluorinated complexes. Density functional theory (DFT) and time-dependent DFT computations corroborate the nature of the excited state as being a hybrid between the metal-to-ligand charge transfer (^1,3MLCT) for the trans-Pt(PBu₃)₂(CCAr)₂ unit, [Pt] and the metal-to-ligand/ligand-to-ligand′ charge transfer (^1,3ML′CT/LL′CT) for [Ir] with L = dFMeppy. Overall, the fluorination of the phenylpyridine group expectedly does not change the nature of the excited state but desirably induces a small blue shift of the absorption and emission bands along a slight decrease in emission quantum yields and lifetimes.

Very Complex Emission Properties of the Pt-Organometallic Versions of PANI. Shawkat M. Aly, Tommy Kenny, Simon Lamarre, and Pierre D. Harvey. Journal of Inorganic and Organometallic Polymers and Materials, 2015, 25, 118-125. https://doi.org/10.1007/s10904-014-0109-x

Abstract: The rather complex emission pattern of polymers of the types ([Pt]-[Q])_n and ([Pt]-[DAB])_n ([Pt] = trans-bis(tributylphosphine)bis(phenylacetynyl)platinum(II); [Q] = substituted quinone diimine; [DAB] = substituted diaminobenzene; X = H, F, Cl) as organometallic versions of polyaniline, PANI, have been addressed using various models. Both the fluorescence and phosphorescence spectra at 77 K originate from [Q] or/and [DAB] residues as the main component or “impurities”, regardless of the polymer or model studied. However at 298 K, this chromophore is completely silent and only a weak fluorescence arising from the [DAB] fragment is observed, either as a part in the chain but also as an unavoidable impurity due to the nature of the redox aspects of the two units.

Ultrafast energy transfer in a Pd(ii)-bridged bisporphyrin dyad. Mohammed Abdelhameed, Adam Langlois, Paul-Ludovic Karsenti, Sébastien Richeter, Romain Ruppert, and Pierre D. Harvey. Chemical Communications, 2014, 50, 14609-14612. https://doi.org/10.1039/C4CC05898D

Abstract: A free base porphyrin/zinc(II)porphyrin dyad bridged by a Pd(II) unit exhibits an ultrafast S₁ energy transfer (1.5 × 10¹² s⁻¹) due to significant MO couplings between the acceptor and the donor and a non-nil atomic contribution of the Pd-atom in the frontier MOs, hence ensuring π-conjugation.

Copper(I) Halides (X = Br, I) Coordinated to Bis(arylthio)methane Ligands: Aryl Substitution and Halide Effects on the Dimensionality, Cluster Size, and Luminescence Properties of the Coordination Polymers. Michael Knorr, Abdeharrim Khatyr, Ahmed Dini Aleo, Anass El Yaagoubi, Carsten Strohmann, Marek M. Kubicki, Yoann Rousselin, Shawkat M. Aly, Daniel J. Fortin, Anthony Lapprand, and Pierre D. Harvey. Crystal Growth and Design, 2014, 14(11), 5373-5387. https://doi.org/10.1021/cg500905z

Abstract: Bis(phenylthio)methane (L1) reacts with CuI to yield the 1D-coordination polymer [{Cu₄(μ₃-I)₄}(μ-L1)₂]_n (1) bearing cubane Cu₄I₄ clusters as connecting nodes. The crystal structures at 115, 155, 195, and 235 K provided evidence for a phase transition changing from the monoclinic space group C2/c to P2₁/c. The self-assembly process of CuI with bis(p-tolylthio)methane (L2), bis(4-methoxyphenylthio)methane (L3), and bis(4-bromo-phenylthio)methane (L4) affords the 1D-coordination polymers [{Cu₄(μ₃-I)₄}(μ-Lx)₂]_n (x = 2, 3, or 4). Compounds 2 and 4 are isostructural with C2/c low temperature polymorph of 1, whereas the inversion centers and 2-fold axes are lost in 3 (space group Cc). The use of bis(m-tolylthio)methane (L5) has no impact on the composition and overall topology of the resulting 1D ribbon of [{Cu₄(μ₃-I)₄}(μ-L5)₂]_n (5). Even the coordination of the sterically crowded dithioether bis(5-tert-butyl-2-methylphenylthio)methane (L8) does not alter the network topology generating the 1D polymer [{Cu₄(μ₃-I)₄}(μ-L8)₂]_n (8). The 1D polymer [{Cu(μ₂-Br)₂Cu}(L1)₂] (9) results from the coordination of L1 with CuBr in a 1:1 metal-to-ligand ratio. In contrast to the mean Cu···Cu distances, which are <2.8 Å noted for the Cu₄(μ₃-I)₄ clusters in the 1D polymers 1–8, the Cu···Cu contact within the Cu(μ₂-Br)₂Cu rhomboids of 9 [2.9194(8) Å] is above the sum of the van der Waals radii of two Cu atoms. The structural arrangement of 1D polymer [{Cu(μ₂-Br)₂Cu}(L3)₂]_n (11) is quite similar to that of 9. While the reaction of CuBr with L5 results in a similar 1D polymer [{Cu(μ₂-Br)₂Cu}(L5)₂]_n (12), the reaction of CuBr with L2 leads to the dinuclear complex [{Cu(μ₂-Br)₂Cu}(η¹-L2)₄] (10) ligated by four pendent bis(p-tolylthio)methane ligands. The ligation of bis(o-tolylthio)methane, L6, on CuBr also yields a discrete complex [{Cu(μ₂-Br)₂Cu}(MeCN)₂(η¹-L6)₂] (13) bearing MeCN and dangling dithioether ligands. A strong luminescence is detected for all CuI polymers, all exhibiting emission lifetimes in the microsecond time scale (i.e., phosphorescence). The polymers containing the Cu₄I₄ core (1–8) exhibit the typically observed low-energy band and sometimes a weaker high-energy band. The nature of the low-energy band was proposed based on literature DFT and TDDFT computations and is predicted to be a mixture of cluster-centered (CC*) and metal/halide-to-ligand charger transfer (M/XLCT). An approximate relationship between the Cu···Cu distance and the emission maxima corroborates the CC* contribution to the nature of the excited states. The emission of the rhomboid-containing materials is assigned to M/XLCT based on literature works on similar motifs.

A drastic substituent effect on the emission properties of quinone diimine models and valuable insight into the excited states of emeraldine. Mohammed Abdelhameed, Adam Langlois, Daniel J. Fortin, Paul-Ludovic Karsenti, and Pierre D. Harvey. Chemical Communications, 2014, 50, 11214-11217. https://doi.org/10.1039/C4CC05178E

Abstract: The (α-NR,α′-NR,N,N′-(C₆H₄CCSiMe₃)₄)[Q] models ([Q] = –NC₆H₄N–) exhibit upper excited state emissions S_n,T_n → S₀ (n >1, R = Boc), similar to emeraldine, vs. a fluorescence S₁ → S₀ (R = H), driven by a large change in dihedral angles made by the NR–C₆H₄ and [Q] planes and intramolecular H-bonds.

Maple™-assisted calculations of the J-integral: a key parameter for the understanding of excited state energy transfer in porphyrins and other chromophores. Adam Langlois and Pierre D. Harvey. Journal of Porphyrins and Phthalocyanines, 2014, 18(08-09), 666-674. https://doi.org/10.1142/S1088424614500400

Abstract: The spectral overlap between the emission of a donor molecule and the absorption of an acceptor molecule, quantifiable using the J-integral calculation, is a parameter of extreme importance when studying the excited state energy transfer by either the Főrster or Dexter mechanism. Despite its extreme importance in both mechanisms, it is often misinterpreted, approximated or incorrectly calculated. The calculation of the J-integral is not trivial especially when one wishes to carry out the calculation on measured spectroscopic data. A detailed description for the correct calculation of the J-integral is herein reported and presents a Maple™ assisted template that is capable of performing this calculation in the two different energy scales (nm and cm^-1) to yield the value of the J-integral in given units. Specific examples using porphyrin-containing compounds are provided. This Maple™ program is flexible and can be easily adapted to the needs of a researcher. A call for the standardization of the calculation of the J-integral for the facile comparison with other overlap integrals found in the literature is made.

DMAP-BODIPY Alkynes: A Convenient Tool for Labeling Biomolecules for Bimodal PET–Optical Imaging. Bertrand Brizet, Victor Gonclaves, Claire Bernhard, Pierre D. Harvey, Franck Denat, and Christine Goze. Chemistry, a European Journal, 2014, 20(40), 12933-12944. https://doi.org/10.1002/chem.201402379

Abstract: Several new boron dipyrromethene/N,N-dimethylaminopyridine (BODIPY-DMAP) assemblies were synthesized as precursors for bimodal imaging probes (optical imaging, OI/positron emission tomography, PET). The photophysical properties of the new compounds were also studied. The first proof-of-concept was obtained with the preparation of several new BODIPY-labeled bombesins and evaluation of the affinity for bombesin receptors by using a competition binding assay. Fluorination reactions were investigated on DMAP-BODIPY precursors as well as on DMAP-BODIPY-labeled bombesins. Chemical modifications on the BODIPY core were also performed to obtain luminescent dyes emitting in the therapeutic window (650–900 nm), suitable for in vivo imaging, making these compounds promising precursors for PET/optical dual-modality imaging agents.

Unexpected Drastic Decrease in the Excited-State Electronic Communication between Porphyrin Chromophores Covalently Linked by a Palladium(II) Bridge. Mohammed Abdelhameed, Paul-Ludovic Karsenti, Adam Langlois, Dean-François Lefebre, Sébastien Richeter, Roman Ruppert, and Pierre D. Harvey. Chemistry, a European Journal, 2014, 20(40), 12988-13001. https://doi.org/10.1002/chem.201403146

Abstract: A dyad built up of a zinc(II) porphyrin and the corresponding free base, [Zn-Fb], fused to N-heterocyclic carbene (NHCs) ligands, respectively acting as singlet energy donor and acceptor, and a bridging trans-PdI₂ unit, along with the corresponding [Zn-Zn] and [Fb-Fb] dimers were prepared and investigated by absorption and emission spectroscopy and density functional computations. Despite favorable structural and spectroscopic parameters, unexpectedly slow singlet energy transfer rates are measured in comparison with the predicted values by the Förster theory and those observed for other structurally related dyads. This observation is rationalized by the lack of large molecular orbital (MO) overlaps between the frontier MOs of the donor and acceptor, thus preventing a double electron exchange through the trans-PdI₂ bridge, and by an electronic shielding induced by the presence of this same linker preventing the two chromophores to fully interact via their transition dipoles.

Slow and Fast Singlet Energy Transfers in BODIPY-gallium(III)corrole Dyads Linked by Flexible Chains. Bertrand Brizet, Nicolas Desbois, Antoine Bonnot, Adrien Dubois, Jean-Michel Barbe, Christine Goze, Franck Denat, and Pierre D. Harvey. Inorganic Chemistry, 2014, 53(7), 3392-3403. https://doi.org/10.1021/ic402798f

Abstract: Red (no styryl), green (monostyryl), and blue (distyryl) BODIPY-gallium(III) (BODIPY = boron-dipyrromethene) corrole dyads have been prepared in high yields using click chemistry, and their photophysical properties are reported. An original and efficient control of the direction of the singlet energy transfers is reported, going either from BODIPY to the gallium-corrole units or from gallium-corroles to BODIPY, depending upon the nature of the substitution on BODIPY. In one case (green), both directions are possible. The mechanism for the energy transfers is interpreted by means of through-space Förster resonance energy transfer (FRET).

Antenna effects in truxene-bridged BODIPY triarylzinc(ii)porphyrin dyads: evidence for a dual Dexter–Förster mechanism. Hai-Jun Xu, Antoine Bonnot, Paul-Ludovic Karsenti, Adam Langlois, Mohammed Abdelhameed, Jean-Michel Barbe, Claude P. Gros, and Pierre D. Harvey,. Dalton Transactions, 2014, 43, 8219-8229. https://doi.org/10.1039/C3DT53630K

Abstract: The antenna process from an energy donor (BODIPY; 4′,4′-difluoro-1′,3′,5′,7′-tetramethyl-4′-bora-3a′,4a′-diaza-s-indacene) in its singlet state to two acceptors (two zinc(II) 5,15-p-tolyl-10-phenylporphyrin) bridged by a central truxene residue (5′,5′′,10′,10′′,15′,15′′-hexabutyltruxene), 5, has been analysed by means of comparison of the energy transfer rates with those of a structurally similar β-substituted BODIPY-(zinc(II) 5,10,15-p-tolyl-porphyrin), 6, where no conjugation is present between the donor and the two acceptors using the Förster resonance energy transfer (FRET) approximation. It is estimated that the energy transfer in 5 operates mostly via a Dexter mechanism (>99%), and the remaining proceeds via a Förster mechanism (<1%). This information is useful for the design of future molecular devices aimed at harvesting light.

Drastic Tuning of the Photonic Properties of «(Push–Pull)_n» trans-Bis(ethynyl)bis(Tributylphosphine)Platinum(II)-Containing Polymers. Xiaorong Wang, Daniel J. Fortin, Gessie Brisard, and Pierre D. Harvey. Macromolecular Rapid Communications, 2014, 35(10), 992-997. https://doi.org/10.1002/marc.201400018

Abstract: The trans-Pt(PBu₃)₂Cl₂ complex reacts with 1 equiv. of 2,6-diethynyl-AQ and 2 equiv. of 2-ethynyl-AQ (AQ = anthraquinone) to form the polymer (trans-Pt(2,6-diethynyl-AQ)₂(PBu₃)₂)_n, 1, and the model compounds, 2, trans-Pt(PBu₃)₂(2-ethynyl-AQ)₂ (in a 20:1 ratio as trans-(2a) and cis-(2b) rotational isomers), respectively. These redox-active and luminescent materials have been characterized by gel permeation chromatography, thermal gravimetric analysis, X-ray crystallography, electrochemistry, photophysics, and DFT computations (B3LYP). The typical π,π* T₂→S₀ phosphorescence centered on the trans-Pt(PBu₃)₂(aryl)₂ chromophore, [Pt], generally encountered for the analogous polymers (trans-Pt(PBu₃)₂(aryl)₂-acceptor)_n (acceptor = quinonediimine, QN₂; anthraquinone diimine, AQN₂), for which the CT T₁→S₀ emission is silent, has been completely annihilated and replaced by a red-shifted T₁→S₀ emission in 1 and 2a, which arise from a triplet charge transfer excited state [Pt]→AQ.

What can we learn from artificial special pairs? Pierre D. Harvey. Canadian Journal of Chemistry, 2014, 92(5), 355-368.https://doi.org/10.1139/cjc-2013-0570

Abstract: Plants and photosynthetic bacteria obtain their energy from sunlight or surrounding radiation. Their photosynthetic membranes are composed of a much elaborated series of antenna molecules based on chlorophylls or bacteriochlorophylls, carotenoids playing multiple roles, various electron transport accessories, and central special pairs. The latter components are the most difficult to mimic with exactitude because the structure−property relationship depends on many factors including interplanar distance, slip angle, substituents, metal, and axial ligand. To this list of factors to control with quasi-perfection, one should also add the thermal activation (i.e., temperature). Over the past 15 years or so (2001–2013), an intensive collaboration with Professor Roger Guilard (Université de Bourgogne, Dijon) dealt with elucidating the role of each parameter to provide the best design of artificial special pairs capable of responding or behaving like the natural special pairs, namely with regards with the antenna effect. The latest feature is one of the defence mechanisms slowing down the rate for the primary electron transfer from the special pair to the electron transport accessories. This review highlights the advances in this challenging area of mimicry of the photophysical events in biological systems, namely the artificial special pairs designed in our laboratory for the antenna processes.

Résumé: Les végétaux et les bactéries photosynthétiques puisent leur énergie dans la lumière du soleil ou les rayonnements environnants. Leurs membranes photosynthétiques sont composées d’une série complexe d’antennes, systèmes molécules formés de chlorophylles ou bactériochlorophylles, de caroténoïdes aux rôles multiples, de divers dispositifs de transport électronique et de paries centrales spéciales. Ces derniers composants sont les plus difficiles à reproduire avec précision car la relation entre structure et propriété dépend de nombreux facteurs parmi lesquels la distance interplanaire, l’angle de glissement, les substituants, le métal et le ligand axial. À cette liste de facteurs à contrôler avec quasi-perfection, il faut ajouter l’activation thermique (c.-à-d. la température). Au cours des 12 dernières années (plus exactement entre 2001 et 2013), une collaboration active avec le professeur Roger Guilard (de l’Université de Bourgogne, à Dijon) a eu pour objectif d’élucider le rôle de chacun des paramètres afin de concevoir, de façon optimale, des paires spéciales artificielles capables de réagir ou de se comporter comme les paires spéciales naturelles, notamment en ce qui concerne l’effet produit par les antennes. La dernière caractéristique est l’un des mécanismes de défense qui diminue le taux du transfert électronique primaire de la paire spéciale vers les dispositifs de transport électronique. La présente étude les avancées réalisées dans le domaine de la reproduction des phénomènes photophysiques présents dans les systèmes biologiques, en particulier la conception, dans notre laboratoire, de paires spéciales artificielles destinées à être utilisées dans les processus qui ont lieu au niveau des antennes. [Traduit par la Rédaction]

High Yield S_NAr on 8-Halogenophenyl-BODIPY with Cyclic and Acyclic Polyamines. Yulia Volkova, Bertrand Brizet, Pierre D. Harvey, Franck Denat, Christine Goze. European Journal of Organic Chemistry, 2014, 11, 2268-2274. https://doi.org/10.1002/ejoc.201301900

Abstract: Selective nucleophilic aromatic substitutions with several polyamines were performed in very good yields on halogeno-phenyl BODIPY derivatives containing an activating nitro group.

A ratiometric “two-in-one” fluorescent chemodosimeter for fluoride and hydrogen sulfide. Li Fu, Fang-Fang Tian, Lu Lai, Yi Liu, Pierre D. Harvey, and Feng-Lei Jiang. Sensors and Actuators B: Chemical, 2014, 193, 701-707. https://doi.org/10.1016/j.snb.2013.12.038

Abstract: Styryl-BODIPY containing 2,4-dinitrobenzenesulfonyl, DNBS, and trihexylsilylacetylene units, THS, shows fast and high differential responses for fluoride and hydrogen sulfide sensing. The chemodosimeter can sense F⁻ expressed by a large 60 nm blue-shift of the fluorescence band as well as an emission intensity enhancement with a lower detection limit of 14.5 nM, while it can also sense HS⁻ by fluorescence in a quasi-OFF-ON manner with a 10-nm red-shift of the luminescence band. The fluorescence of the probe is stable and pH-independent in the physiological pH range. To the best of our knowledge, this is the first report on the single fluorescent molecule sensing both F⁻ and HS⁻ each with distinct spectroscopic responses. Finally, the probe has been used successfully for bioimaging the hydrogen sulfide in living cells. This “two-in-one” design strategy will inspire more multimodal agents for various applications.

Origin of the temperature dependence of the rate of singlet energy transfer in a three-component truxene-bridged dyads. Adam Langlois, Hai-Jun Xu, Bertrand Brizet, Franck Denat, Jean-Michel Barbe, Claude P. Gros, and Pierre D. Harvey. Journal of Porphyrins and Phthalocyanines, 2014, 18(01-02), 94-106. https://doi.org/10.1142/S1088424613501150

Abstract: We report a truxene-based dyad built upon one donor (tri-meso-phenylzinc(II)porphyrin) and two acceptors (octa-β-alkylporphyrin free base) in which the donor exhibits free rotation around a C_truxene-C_meso single bond at 298 K in fluid solution but not at 77 K in a glass matrix, whereas the acceptors have very limited motion as they are blocked by β-methyl groups. This case is interesting because all the structural and spectroscopic parameters affecting the rate for singlet energy transfer according to a Förster Resonance Energy Transfer are only weakly temperature dependent, leaving only the Dexter mechanism explaining the larger variation in rate of energy transfers with the temperature hence providing a circumstantial evidence for a dual mechanism (Föster and Dexter) in truxene-based dyads (or polyads) in the S₁ excited states.

Electronic communication across N-linked unconjugated polymers: important insight into the charge transfer processes of polyaniline. Xiaorong Wang, Daniel J. Fortin, Gessie Brisard, and Pierre D. Harvey. Chemical Communications, 2014, 40, 350-352. https://doi.org/10.1039/C3CC47092J

Abstract: The [C₆H₄CCPtL₂CCC₆H₄] → quinone charge transfer bands in unconjugated ([Pt]–NMe–Q)_n's are similar to the conjugated systems showing that the NMe secures communication.

Metal-to-Ligand Ratio Effect on the Size of Copper Iodide and Copper Bromide Clusters in 1,4-Bis(cyclohexylthio)butane-Spanned Coordination Polymers. Antoine Bonnot, Carsten Sthromann, Michael Knorr, and Pierre D. Harvey. Journal of Cluster Science, 2014, 25, 261-275. https://doi.org/10.1007/s10876-013-0637-5

Abstract: The CuX salts (X = Br, I) react with 1,4-bis(cyclohexylthio)butane, L2, in a 1:1 ratio to form the corresponding isostructural and weakly luminescent 1D coordination polymers [(Cu₂X₂)(μ-L2)₂]_n(X = Br, 4; X = I, 3) as determined by X-ray crystallography. The previously reported reaction of CuI with 1,4-bis(phenylthio)butane, L1, in a 2:1 metal-to-ligand ratio provides a 2D polymer [(Cu₄I₄)(μ-L1)₂]_n, 1 (Knorr et al., Dalton Trans 38:948–955, 2009), where the Cu₄I₄ unit exhibits the common cubane structure and an intense luminescence centered at 555 and 565 nm respectively at 298 and 77 K. When CuI reacts with L2 in a 2:1 metal-to-ligand ratio, a new material 2 is formed but no X-ray structure was obtained. The intense and characteristic luminescence of polymer 2 is strongly indicative of the formation of the cubane Cu₄I₄ unit. The new materials have been characterized by solid-state UV–Vis rasing-angle transmittance spectroscopy, luminescence spectroscopy and emission lifetime measurements.

Cluster-Containing Coordination Polymers Built Upon (Cu₂I₂S₂)_m Units (m = 2, 3) and ArSCH₂C≡CCH₂SAr Ligands: Is the Cluster Size Dependent Upon Steric Hindrance or Ligand Rigidity? Shawkat M. Aly, Abdoulaye Pam, Abderrahim Khatyr, Michael Knorr, Yoann Rousselin, Marek M. Kubicki, Jonathan O. Bauer, Carsten Strohmann, and Pierre D. Harvey. Journal of Inorganic and Organometallic Polymers and Materials, 2014, 24, 190-200. https://doi.org/10.1007/s10904-013-9984-9

Abstract: Two equivalents of CuI react with p-MeC₆H₄SCH₂C≡CCH₂SC₆H₄-p-Me (L2) to form the 2D network [(Cu₄I₄)(p-MeC₆H₄SCH₂C≡CCH₂SC₆H₄-p-Me)₂]_n(polymer 2) contrasting with the previously reported reaction with C₆H₅SCH₂C≡CCH₂SC₆H₅ (L1) which makes a 3D network [(Cu₆I₆)(C₆H₅SCH₂C≡CCH₂SC₆H₅)₃]_n(polymer 1) (2009, Dalton Trans. 948). The crystal structure of the latter polymer has been re-determined at 115, 155, 195, 235 and 275 K to study the impact of the recording temperature on the metric parameters, notably the Cu···Cu distances within the hexagonal prism Cu₆I₆ cluster. Steric hindrance between a 2D/(Cu₄I₄) versus 3D/(Cu₆I₆) appears to drive the selectivity. Upon using the ligand o-MeC₆H₄SCH₂C≡CCH₂SC₆H₄-o-Me (L3) with CuI, a new material (polymer 3) is formed but no X-ray structure determination was possible. From obvious steric considerations and the presence of a high energy emission characteristic of the well-known Cu₄I₄ cluster (absent in the Cu₆I₆ one), and the similarity in emission lifetime for both high and low energy emission of polymers 2 and 3, the nature of this polymer was proposed to be [(Cu₄I₄)(o-MeC₆H₄SCH₂C≡CCH₂SC₆H₄-o-Me)₂]_n.

Boron functionalization of BODIPY by various alcohols and phenols. Bertrand Brizet, Claire Bernhard, Yulia Volkova, Yoann Rousselin, Pierre D. Harvey, Christine Goze, and Franck Denat. Organic & Biomolecular Chemistry, 2013, 11, 7729-7737. https://doi.org/10.1039/C3OB41370E

Abstract: The synthesis of new B–O BODIPY derivatives functionalized with different alkoxy or diarylalkoxy derivatives is described. These compounds were synthesized from the reaction of different B–F BODIPY precursors with various alcohols and phenols, in the presence of AlCl₃. Water-soluble dyes could be synthesized as well with this method, specifically by the introduction of polyethyleneglycol (PEG) groups. A photophysical study of the different compounds was performed, and showed that the B–O BODIPY derivatives exhibit rich fluorescence properties. Finally, the conjugation of the BODIPY core has been extended using two distyryl groups, hence providing NIR emitting BODIPY derivatives, in which one or two PEG groups have been anchored, making these systems very promising for future medical imaging applications.

Formation of an unprecedented (CuBr)₅ cluster and a zeolite-type 2D-coordination polymer: a surprising halide effect. Anthony Lapprand, Antoine Bonnot, Michael Knorr, Youann Rousselin, Marek M. Kubicki, Daniel Fortin, Pierre D. Harvey. Chemical Communications, 2013, 49, 8848-8850. https://doi.org/10.1039/C3CC45284K

Abstract: A unique pentanuclear cluster within a zeolite-type polymer ([Cu₅(μ₄-Br)(μ₃-Br)₂(μ₂-Br)₂](μ₂-MeSPr)₃)_n (1; void space >81%) and a luminescent 1D ([Cu(μ₃-I)]₄(MeSPr)₃)_n polymer, 2, are formed when MeSPr reacts with CuBr and CuI.

Design of Triads for Probing the Direct Through Space Energy Transfers in Closely Spaced Assemblies. Jean-Michel Camus, Shawkat M. Aly, Daniel J. Fortin, Roger Guilard, and Pierre D. Harvey. Inorganic Chemistry, 2013, 52(15), 8360-8368. https://doi.org/10.1021/ic3026655

Abstract: Using a selective stepwise Suzuki cross-coupling reaction, two trimers built on three different chromophores were prepared. These trimers exhibit a D^∧A₁-A₂ structure where the donor D (octa-β-alkyl zinc(II)porphyrin either as diethylhexamethyl, 10a, or tetraethyltetramethyl, 10b, derivatives) through space transfers the S₁ energy to two different acceptors, di(4-ethylbenzene) zinc(II)porphyrin (A₁; acceptor 1) placed cofacial with D, and the corresponding free base (A₂; acceptor 2), which is meso–meso-linked with A₁. This structure design allows for the possibility of comparing two series of assemblies, 9a,b (D^∧A₁) with 10a,b (D^∧Â₁-A₂), for the evaluation of the S₁ energy transfer for the global process D*→A₂ in the trimers. From the comparison of the decays of the fluorescence of D, the rates for through space energy transfer, k_ET for 10a,b (k_ET ≈ 6.4 × 10⁹ (10a), 5.9 × 10⁹ s^–1 (10b)), and those for the corresponding cofacial D^∧A₁ systems, 9a,b, (k_ET ≈ 5.0 × 10⁹ (9a), 4.7 × 10⁹ s^–1 (9b)), provide an estimate for k_ET for the direct through space D*→A₂ process (i.e., k_ET(D^∧A₁-A₂) – k_ET(D^∧A₁) = k_ET(D*→A₂) ∼ 1 × 10⁹ s^–1). This channel of relaxation represents ∼15% of k_ET for D*→A₁.

Luminescent P-Chirogenic Copper Clusters. Antony Lapprand, Mathieu Dutartre, Naïma Khiri, Etienne Levert, Daniel J. Fortin, Yoann Rousselin, Armand Soldera, Sylvain Jugé, and Pierre D. Harvey. Inorganic Chemistry, 2013, 52(14), 7958-7967. https://doi.org/10.1021/ic400498j

Abstract: P-chirogenic clusters of the cubanes [Cu₄I₄L₄] (L = chiral phosphine) were prepared from (+)- and (−)-ephedrine with L = (S)- or (R)-(R)(Ph)(i-Pr)P (with R = CH₃ (seven steps) or C₁₇H₃₅ (10 steps)) with e.e. up to 96%. The X-ray structure of [Cu₄I₄((R)-(CH₃)(Ph)(i-Pr)P)₄] confirmed the cubane structure with average Cu···Cu and Cu···I distances of 2.954 and 2.696 Å, respectively. The cubane structure of the corresponding [Cu₄I₄((S)-(CH₃)(Ph)(i-Pr)P)₄] was established by the comparison of the X-ray powder diffraction patterns, and the opposite optical activity of the (S)- and (R)-ligand-containing clusters was confirmed by circular dichroism spectroscopy. Small-angle X-ray scattering patterns of one cluster bearing a C₁₇H₃₅ chain exhibit a weak signal at 2θ ∼ 2.8° (d ∼ 31.6 Å), indicating some molecular ordering in the liquid state. The emission spectra exhibit two emission bands, both associated with triplet excited states. These two bands are assigned as follows: the high energy emission is due to a halide-to-ligand charge transfer, XLCT, state mixed with LXCT (ligand-to-halide-charge-transfer). The low energy band is assigned to a cluster-centered excited state. Both emissions are found to be thermochromic with the relative intensity changing between 77 and 298 K for the clusters in methylcyclohexane solution. Several differences are observed in the photophysical parameters, emission quantum yields and lifetimes for R = CH₃ and C₁₇H₃₅. The measurements of the polarization along the emission indicate that the emission is depolarized, consistent with an approximate tetrahedral geometry of the chromophores.

Monitoring the on–off switching of the electronic communication in diethynylplatinum(ii)-bridged dyads using triplet energy transfer. Ahmed M. Soliman, Mohammed Abdelhameed, Eli Zysman-Colman, and Pierre D. Harvey. Chemical Communications, 2013, 49, 5544-5546. https://doi.org/10.1039/C3CC42634C

Abstract: Despite conjugation and downhill manifolds in [Ir]–[Pt]–[ZnTPP] ([ZnTPP] = (tetraphenylporphyrin)zinc(II), [Ir] = bis(phenylpyridinato)(bipyridine)iridium(III), [Pt] = trans-CCPt(PBu₃)₂-CC), essentially no T₁[Ir] → S₁/T₁[ZnTTP] energy transfer occurs.

P-Chirogenic Phosphines Supported by Calix[4]arene: New Insight into Palladium-Catalyzed Asymmetric Allylic Substitution. Naïma Khiri-Meribout, Etienne Bertrand, Jérôme Bayardon, Marie-Joëlle Eymin, Yoann Rousselin, Hélène Cattey, Daniel J. Fortin, and Pierre D. Harvey. Organometallics, 2013, 32(9), 2827-2839. https://doi.org/10.1021/om400229p

Abstract: The first P-chirogenic mono- and diphosphine ligands supported on the upper rim of a calix[4]arene moiety were synthesized using the ephedrine methodology. The lithiated calix[4]arene mono- and dianions both react with the oxazaphospholidine–borane, prepared from ephedrine, to afford regio- and stereoselectively the corresponding calix[4]arenyl aminophosphine–boranes, by cleavage of the heterocyclic ring at the P–O bond position. Subsequent reactions with HCl and then organolithium reagent and finally decomplexation with DABCO lead to the corresponding calix[4]arenyl mono- or diphosphines. Both enantiomers of the calix[4]arenyl phosphines were obtained either by using (+)- or (−)-ephedrine or by changing the addition order of the organolithium reagents during the synthesis. The enantiomeric excesses of the phosphines were determined either by HPLC on a chiral column of their borane complexes or by ³¹P NMR in the presence of a chiral palladium complex. The absolute configurations of the mono- and diphosphinocalix[4]arenes were assigned by X-ray analysis of their crystalline borane complexes. The P-chirogenic calix[4]arenyl phosphines were tested for asymmetric palladium-catalyzed allylic substitution of (E)-1,3-diphenylprop-2-en-1-yl acetate, by dimethyl malonate or benzylamine. When the bis-methylphenylphosphino calix[4]arene was used, the allylic products were obtained with 82% and 79% ee, respectively. In both cases, the use of a diphosphine affords better results than using 2 equivalents of monophosphine. Despite the C₂ symmetry of the P-chirogenic diphosphine calix[4]arene ligand, computer modeling of the corresponding Pd(allyl) complex shows a clear dissymmetry of the LUMO, which is in good agreement with a complexed η¹-allyl moiety and with the regio- and enantioselectivity of the Pd-catalyzed allylations.

BODIPY Dyes Functionalized with Pendant Cyclic and Acyclic Polyamines. Yulia A. Volkova, Bertrand Brizet, Pierre D. Harvey, Alexey D. Averin, Christine Goze, and Franck Denat. European Journal of Organic Chemistry, 2013, 20, 4170-4279. https://doi.org/10.1002/ejoc.201300414

Astract: The synthesis and characterization of a series of BODIPY derivatives substituted with acyclic and cyclic polyamines, in particular, cyclen and homocyclen, are reported. The ¹⁹F NMR, UV/Vis, and fluorescence spectroscopic data of these compounds are discussed. One compound was found to be very selective for Cu^II ions, which makes it a very promising system for Cu^II detection.

Syntheses of Bioinspired Trisporphyrin Scaffoldings from Stepwise Suzuki Coupling Strategies. Jean-Michel Camus, Pierre D. Harvey, and Roger Guilard. Heteromacrocycles, 2013, 6, 13-22. Lien non-disponible.

Abstract: This review presents the synthetic approach for the design of tris (macrocycles) as bio-inspired models for light harvesting devices in plants and photosynthetic bacteria based on cofacial bisporphyrins and a porphyrin unit attached as a side arm. Two types of tris (porphyrins) are described herein depending on the nature of the chromophores of the cofacial bis (porphyrins). The synthetic methodology of a series of trimeric models relies on the versatility of the porphyrin ring acting as a building block, and on successive Suzuki coupling reactions. Various pathways to access such models are presented as the selective and stepwise substitution processes involving different borylated porphyrin synthons can provide either meso-meso-linked linear intermediates or cofacial homo-or hetero-bismacrocycle units. This efficient methodology also allows for the flexibility and fine tuning since different bridges and spacers can be used in the designed trimers.

Evidence for reverse pathways and equilibrium in singlet energy transfers between an artificial special pair and an antenna. Jean-Michel Camus, Adam Langlois, Shawkat M. Aly, Roger Guilard, and Pierre D. Harvey. Journal of Porphyrins and Phthalocyanines, 2013, 17(08-09), 722-732. https://doi.org/10.1142/S108842461350017X

Abstract: A dyad, 1, built on an artificial special pair (bis(meso-nonyl)zinc(II)porphyrin), [Zn₂], a spacer (biphenylene), a bridge (1,4-benzene), and an antenna (di-meso-(3,5-di(t-butyl)phenyl)porphyrin free base), FB, is prepared by Suzuki coupling and is analyzed by absorption and steady state, and time-resolved emission spectroscopy at 298 and 77 K. Using bases from the Förster theory, evidence for two pathways for S₁ energy transfer, FB* → [Zn₂], and [Zn₂]* → FB, along with their respective rates, k_ET(S₁)₁ and k_ET(S₁)_-1, are extracted from the comparison of the fluorescence decays monitored at the emission maximum. At 77 K, the unquenched (1.79 ([Zn₂]) and 10.6 ns (FB)) and quenched components (<100 ps; i.e.k_ET(S₁) > 10 (ns)^-1), are observed, hence, demonstrating the bidirectional paths with no back energy transfer. A 298 K, only two components are detected (0.44 ([Zn₂]) and 2.64 ns (FB)) and the resulting reduced τ_Fs indicates back energy transfer, therefore cycling and equilibrium. Their global rates are 0.31 and 1.8 (ns)^-1 for k_ET(S₁)₁ and k_ET(S₁)_-1 at 298 K. This large temperature dependence on k_ET(S₁) is fully consistent with the participation of thermal activation. Finally, DFT calculations (B3LYP) were used to illustrate a clear correlation between the relative k_ET(S₁)s and the amplitude of the MO couplings between the artificial special pair and the antenna.

Organometallic Oligomers Based on Bis(arylacetylide)bis(P-chirogenic phosphine)platinum(II) Complexes: Synthesis and Photonic Properties. Anthony Lapprand, Maïma Khiri, Daniel J. Fortin, Sylvain Jugé, and Pierre D. Harvey. Inorganic Chemistry, 2013, 52(5), 2361-2371. https://doi.org/10.1021/ic301829x

Abstract: A series of P-chirogenic oligomers of the type (—C≡C—aryl—C≡C—PtL₂—)_n [L = (R)- and (S)-P(Ph)(iPr)(C₁₇H₃₅); aryl = 1,4-benzene, 2,1,3-benzothiadiazole] along the corresponding achiral analogues (L = PBu₃) and model complexes PhC≡CPtL₂C≡CPh were prepared from the ephedrine strategy and were fully characterized [¹H, ³¹P NMR; IR; small-angle X-ray scattering (SAXS); gel permeation chromatography (GPC); thermal gravimetric analysis (TGA); circular dichroism, UV–vis, and luminescence spectroscopy; photophysics, and degree of anisotropy measurements]. From the CD measurements, the chiral environment of the phosphine ligands is modestly felt by the aryl moieties. Concurrently, the TGA shows that the P(C₁₇H₃₅)(Ph)(i-Pr)-containing materials are more stable than those containing the shorter chain ligand PBu₃, and exhibits red-shifted absorption and emission bands compared to those including the PBu₃ ligands. The presence of the long chain on the phosphorus atoms does not greatly alter the photophysical parameters, notably the emission lifetimes, and fast triplet energy transfer terminal* → central unit has been deduced from the absence of luminescence arising from the terminal units.

Is the special pair structure a good strategy for the kinetics during the last step of the energy transfer with the nearest antenna? A chemical model approach. Jean-Michel Camus, Adam Langlois, Sawkat M. Aly, Roger Guilard, and Pierre D. Harvey. Chemical Communications, 2013, 49, 2228-2230. https://doi.org/10.1039/C3CC38740B

Abstract: A cofacial bis(Mg(II)porphyrin)–C₆H₄-free base ([Mg₂]–bridge–FB) dyad shows S₁ energy transfer in both directions and much slower rates than similar monoporphyrin systems are observed.

The Pt-Organometallic Version of Perigraniline: Going Blue. Tommy Kenny, Shawkat M. Aly, Gessie Brisard, Daniel J. Fortin, and Pierre D. Harvey. Macromolecular Rapid Communications, 2013, 34(6), 511-515. https://doi.org/10.1002/marc.201200741

Abstract: Four conjugated push–pull organometallic polymers ([Pt]-AQ)_n ([Pt] = trans-bis(phenylacetylene)bis(tributylphosphine)platinum(II); AQ = 2-bromo-, 2,6-dibromo-, 2,6-diamino-, and unsubstituted anthraquinone diimine) were prepared and characterized by UV–vis spectroscopy and electrochemistry. A low-energy charge transfer, CT, band ([Pt]*→AQ; confirmed by density functional theory calculations), was found in the 445–500 nm window rather than the expected red-shifted range above 630 nm. X-ray structures of four model compounds reveal that steric hindrance induces large dihedral angles between the C₆H₄ and N=CC₂ planes, rendering π-orbital overlap difficult between the [Pt] and AQ units. The position of the CT band is mainly driven the reduction potential of the anthraquinone diimine unit.

Dendron to Central Core S₁–S₁ and S₂–S_n (n>1) Energy Transfers in Artificial Special Pairs Containing Dendrimers with Limited Numbers of Conformations. Pierre D. Harvey, Frédérique Brégier, Shawkat M. Aly, Jędrzej Szmytkowski, Matthew F. Paige, and Ronald P. Steer. Chemistry - A European Journal, 2013, 19(13), 4352-4368. https://doi.org/10.1002/chem.201203033

Abstract: Two dendrimers consisting of a cofacial free-base bisporphyrin held by a biphenylene spacer and functionalized with 4-benzeneoxomethane (5-(4-benzene)tri-10,15,20-(4-n-octylbenzene)zinc(II)porphyrin) using either five or six of the six available meso-positions, have been synthesized and characterized as models for the antenna effect in Photosystems I and II. The presence of the short linkers, -CH₂O-, and long C₈H₁₇ soluble side chains substantially reduces the number of conformers (foldamers) compared with classic dendrimers built with longer flexible chains. This simplification assists in their spectroscopic and photophysical analysis, notably with respect to fluorescence resonance energy transfer (FRET). Both steady-state and time-resolved spectroscopic measurements indicate that the cofacial free bases and the flanking zinc(II)–porphyrin antennas act as energy acceptor and donor, respectively, following excitation in either the Q or Soret bands of the dendrimers. The rate constants for singlet electronic energy transfer (k_EET) extracted from the S₁ and S₂ fluorescence lifetimes of the donor in the presence and absence of the acceptor are ≤ (0.1–0.3)×10⁹ and ∼2×10⁹ s⁻¹ for S₁→S₁ (range from a bi-exponential decay model) and about 1.5×10¹² s⁻¹ for S₂→S_n (n>1). Comparisons of these experimental data with those calculated from Förster theory using orientation factors and donor–acceptor distances extracted from computer modeling suggest that a highly restricted number of the many foldamers facilitate energy transfer. These foldamers have the lowest energy by molecular modeling and consist of one or at most two of the flanking zinc porphyrin antennas folded so they lie near the central artificial special pair core with the remaining antennas located almost parallel to and far from it.

BODIPY-phosphane as a versatile tool for an easy access to new metal-based theranostics. Semra Tasan, Olivier Zava, Julien Pierron, Benoît Bertrand, Claire Bernhard, Christine Goze, Michel Picquet, Pierre Le Gendre, Pierre Harvey, Franck Denat, Angela Casini, and Ewen Bodio. Dalton Transactions, 2013, 42, 6102-6109. https://doi.org/10.1039/C2DT32055J

Abstract: A new BODIPY–phosphane was synthesized and proved to be a versatile tool for imaging organometallic complexes. It also led to easy access to a new family of theranostics, featuring gold, ruthenium and osmium complexes. The compounds’ cytotoxicity was tested on cancer cells, and their cell uptake was followed by fluorescence microscopy in vitro.

A Conjugated Organometallic Polymer with Truxene Antennas as Side Arms; A Multiluminescent Material with Evidence for Intrachain MO Couplings. Bin Du, Daniel J. Fortin, and Pierre D. Harvey. Journal of Inorganic and Organometallic Polymers and Materials, 2013, 23, 81-88. https://doi.org/10.1007/s10904-012-9718-4

Abstract: A polymer ([Pt]–ZnP)_n (ZnP = bis-meso-(hexahexyltruxene)zinc(II) porphyrin; [Pt] = trans-bis(phenylacetylene)bis(tributylphosphine)platinum(II)) was prepared from bis-meso-(hexahexyltruxene)zinc(II) porphyrin and trans-dichlorobis(tributylphosphine)platinum(II) and exhibits fluorescence and phosphorescence from truxene (Tru) and ZnP, and phosphorescence from [Pt] all at once. Evidence for singlet and triplet energy transfer Tru → ZnP (slow), [Pt] → ZnP (fast) is provided indicating inter-chromophore interactions. DFT computations indicate strong MO coupling between [Pt] and ZnP.

Highly efficient iridium(iii) phosphors with phenoxy-substituted ligands and their high-performance OLEDs. Guiping Tan, Shuming Chen, Ning Sun, Yanhu Li, Daniel Fortin, Wai-Yeung Wong, Hoi-Sing Kwok, Dongge Ma, Hongbin Wu, Lixiang Wang, and Pierre D. Harvey. Journal of Materials Chemistry C, 2013, 1, 808-821. https://doi.org/10.1039/C2TC00123C

Abstract: Two new iridium(III) cyclometallated complexes (1 and 2) based on the 2-(1-phenoxy-4-phenyl)-5-methylpyridine ligand have been developed. By attaching a flexible phenoxy group on the phenyl ring of 2-phenylpyridine (Hppy), the light-emitting properties of the resulting Ir^III complexes have been improved, while the introduction of an electron-donating methyl group on the pyridyl ring of Hppy can keep the triplet emission in the green region by compensating for the reduced energy gap caused by the phenoxy group. Owing to the unique electronic structures induced by the ligand, the vacuum-evaporated organic light-emitting devices (OLEDs) of the type [ITO/NPB (40 nm)/(1 or 2):CBP (20 nm)/BCP (10 nm)/Alq₃ (30 nm)/LiF (1 nm)/Al (100 nm)] furnished peak OLED efficiencies at 10.0%, 31.1 cd A⁻¹ and 14.5 lm W⁻¹ for 1 and 11.7%, 38.1 cd A⁻¹ and 31.8 lm W⁻¹ for 2. By replacing the electron-injection/electron-transporting materials (BCP and Alq₃) with TPBi, the green-emitting devices based on 1 gave outstanding peak efficiencies at 22.5%, 76.2 cd A⁻¹ and 72.8 lm W⁻¹. Extremely high peak efficiencies of 24.5%, 84.6 cd A⁻¹ and 77.6 lm W⁻¹ were even obtained for the 2-doped devices and both of them are superior in performance to the benchmark dopants Ir(ppy)₃ and Ir(ppy)₂(acac). Moreover, polymer light-emitting devices were also fabricated using 1 and 2via the spin-coating method, and their device performances are characterized by 14.4%, 39.5 cd A⁻¹ and 12.4 lm W⁻¹ for 1 and 12.6%, 29.6 cd A⁻¹ and 18.1 lm W⁻¹ for 2. When 2 was used to make three-color white-light OLEDs, respectable device efficiencies of 15.3 cd A⁻¹, 7.5% and 9.1 lm W⁻¹ were achieved and their white color CIE coordinates are improved relative to Ir(ppy)₃.

Shape-persistent poly-porphyrins assembled by a central truxene: synthesis, structure, and singlet energy transfer behaviors. Hai-Jun Xu, Claude P. Gros, Philippe Richard, Jean-Michel Barbe, and Pierre D. Harvey. Journal of Porphyrins and Phthalocyanines, 2013, 17(01-02), 44-55. https://doi.org/10.1142/S1088424612501271

Abstract: Four dyad systems composed of a central truxene and either one or three β-substituted zinc(II) porphyrins (ZnP: TruZnP (7) and TruTriZnP (9)) or free-bases (H₂P: TruP (6) and TruTriP (8)) have been prepared. The presence of β-methyl groups minimizes π-conjugation through the quasi right angle made by the porphyrin and the truxene planes, and renders these dyads relatively rigid. The position of the absorption and emission 0–0 peaks confirms the role of the truxene and porphyrin as the energy donor and acceptor, respectively. Selective excitation of the truxene results in an efficient singlet energy transfer (S₁ ET) from the truxene to the porphyrin unit. The rates for S₁ ET (k_ET) are extracted from the change in the fluorescence lifetime of truxene in the presence and absence of the acceptor, and are temperature independent, (TruP (6), TruTriP (8), TruZnP (7) and TruTriZnP (9) are 5.0, 1.4, 1.0 and 1.4 at 298 K and 5.9, 1.3, 2.6, and 0.86 (ns)^-1 at 77 K, respectively), consistent with their relative rigidity. These k_ET's are similar to other related but more flexible systems reported by one of us (Inorg. Chem.2011, 50, 11493–11505). The k_ET's time scale was assumed, based on modeling, to be related with hindered rotations about the truxene-porphyrin C–C bonds due to steric hexyl–hexyl interactions. This work confirms this earlier conclusion was correct.

Reduced and Oxidized Forms of the Pt-Organometallic Version of Polyaniline. Tommy Kenny, Simon Lamare, Sawkat M. Aly, Daniel J. Fortin, Gessie Brisard, and Pierre D. Harvey. Inorganic Chemistry, 2012, 51(24), 13081-13095. https://doi.org/10.1021/ic300775n

Abstract: This work represents an effort to synthesize all four forms of polyaniline (PANI) in its organometallic versions. Polymers containing substituted 1,4-benzoquinone diimine or 1,4-diaminobenzene units in the backbone exhibiting the general structure (C≡CC₆H₄–N═C₆X₄═N–C₆H₄C≡C-PtL₂)_n and (C≡CC₆H₄NH-C₆X₄-NHC₆H₄C≡C-PtL₂)_n along with the corresponding model compounds (C≡CC₆H₄–N═C₆X₄═N–C₆H₄C≡C)(PtL₂Cl)₂ and (C≡CC₆H₄NH-C₆X₄-NHC₆H₄C≡C)(PtL₂Cl)₂ (L = PBu₃; X = H, F, Cl) were synthesized. The polymers and corresponding model compounds were characterized (including ¹H and ³¹P NMR, IR, mass spectra, elemental analysis, and X-ray structure determinations) and investigated for their redox properties in the absence and in the presence of acid. Their optical properties, including ns transient spectroscopy were also investigated. These properties were interpreted through density functional theory (DFT) and time-dependent DFT (TDDFT) computations. These materials are found to be oligomers (GPC) with thermal stability (TGA) reaching 350 °C. The greatest stabilities were found in the cases with X = F. Using a data bank of 8 X-ray structures of diimine derivatives, a relationship between the C═N bond distance and the dihedral angle between the benzoquinone ring and the flanking phenyl planes is noted. As the size of the substituent X on the benzoquinone center increases, the degree of conjugation decreases as demonstrated by the C═N bond length. The largest dihedral angles are noted for X = Cl. These polymers exhibit drastic chemical differences when X is varied (X = H, F, Cl). The completely reduced polymer (C≡CC₆H₄NH-C₆H₄–NHC₆H₄C≡C-PtL₂)_n (i.e., X = H) was not chemically accessible whereas in the cases of X = F, Cl, these materials were obtained and represent the first examples of fully reduced organometallic versions of PANI (i.e., leucoemaraldine). For the (C≡CC₆H₄–N═C₆X₄═N–C₆H₄C≡C-PtL₂)_n polymers, the completely oxidized form for X = H was isolated (pernigraniline), but for X = F and Cl, only the largely reduced mixed-valence form (i.e., emaraldine) was obtained via chemical routes. In acidic solutions, the chemically accessible polymer for X = H, (C≡CC₆H₄–N═C₆H₄═N–C₆H₄C≡C-PtL₂)_n, exhibits two chemically reversible waves indicating that the reduced form (C≡CC₆H₄NH-C₆H₄–NHC₆H₄C≡C-PtL₂)_n can be generated. The absorption spectra of the highly colored diimine-containing species exhibit a broad charge transfer band (assigned based on DFT calculations (B3LYP); C₆H₄C≡C-PtL₂-C≡CC₆H₄ → N═C₆X₄═N) in the 450–800 nm window red shifting according X = H → Cl → F, consistent with their relative inductive effect. The largest absorptivity is measured for X = H because this polymer is fully oxidized whereas for the cases where X = F and Cl, these polymers exists in the mixed valence form. The ns transient absorption spectra of two polymers (X = F; reduced and mixed-valence polymers) were measured. The triplet excited state in the mixed-valence polymer is dominated by the reduced diamine residue and the T₁-T_n absorption of the diimine is entirely quenched.

Convenient tautomeric forms in an amino-anthraquinone diimine for the generation of a mixed-valent push–pull conjugated polymer. Tommy Kenny, Sawkat M. Aly, Daniel J. Fortin, and Pierre D. Harvey. Chemical Communications, 2012, 48, 11543-11545. https://doi.org/10.1039/C2CC36768H

Abstract: The use of NH₂ on the (Pt(CC)₂(PBu₃)₂)_n/anthraquinone diimine)_n polymer induces a tautomeric species which leads to a mixed-valent form reminiscent of emaraldine in polyaniline.

Construction of (CuX)_2n Cluster-Containing (X = Br, I; n = 1, 2) Coordination Polymers Assembled by Dithioethers ArS(CH₂)_mSAr (Ar = Ph, p-Tol; m = 3, 5): Effect of the Spacer Length, Aryl Group, and Metal-to-Ligand Ratio on the Dimensionality, Cluster Nuclearity, and the Luminescence Properties of the Metal–Organic Frameworks. Michael Knorr, Fabrice Guyon, Abderrahim Khatyr, Carsten Strohmann, Magali Allain, Shawkat M. Aly, Anthony Lapprand, Daniel J. Fortin, and Pierre D. Harvey. Inorganic Chemistry, 2012, 51(18)9917-9934.https://doi.org/10.1021/ic301385u

Abstract: Reaction of CuI with bis(phenylthio)propane in a 1:1 ratio yields the two-dimensional coordination polymer [{Cu(μ₂-I)₂Cu}{μ-PhS(CH₂)₃SPh}₂]_n (1). The 2D-sheet structure of 1 is built up by dimeric Cu₂I₂ units, which are connected via four bridging 1,3-bis(phenylthio)propane ligands. In contrast, treatment of 2 equiv of CuI with 1,3-bis(phenylthio)propane in MeCN solution affords in a self-assembly reaction the strongly luminescent metal–organic 2D-coordination polymer [Cu₄I₄{μ-PhS(CH₂)₃Ph}₂]_n (2), in which cubane-like Cu₄(μ₃-I)₄ cluster units are linked by the dithioether ligands. The crystallographically characterized one-dimensional (1D) compound [{Cu(μ₂-Br)₂Cu}{μ-PhS(CH₂)₃SPh}₂]_n (3) is obtained using CuBr. The outcome of the reaction of PhS(CH₂)₅SPh with CuI also depends of the metal-to-ligand ratio employed. Mixing CuI and the dithioether in a 2:1 ratio results in formation of [Cu₄I₄{μ-PhS(CH₂)₅Ph}₂]_n (4) in which cubane-like Cu₄(μ₃-I)₄ clusters are linked by the bridging dithioether ligand giving rise to a 1D necklace structure. A ribbon-like 1D-polymer with composition [{Cu(μ₂-I)₂Cu}{μ-PhS(CH₂)₅SPh}₂]_n (5), incorporating rhomboid Cu₂I₂ units, is produced upon treatment of CuI with 1,5-bis(phenylthio)pentane in a 1:1 ratio. Reaction of CuBr with PhS(CH₂)₅SPh produces the isomorphous 1D-compound [{Cu(μ₂-Br)₂Cu}{μ-PhS(CH₂)₅SPh}₂]_n (6). Strongly luminescent [Cu₄I₄{μ-p-TolS(CH₂)₅STol-p}₂]_n (7) is obtained after mixing 1,5-bis(p-tolylthio)pentane with CuI in a 1:2 ratio, and the 2D-polymer [{Cu(μ₂-I)₂Cu}₂{μ-p-TolS(CH₂)₅STol-p}₂]_n (8) results from reaction in a 1:1 metal-to-ligand ratio. Under the same reaction conditions, 1D-polymeric [{Cu(μ₂-Br)₂Cu}{μ-p-TolS(CH₂)₅STol-p}₂]_n (9) is formed using CuBr. This study reveals that the structure of the self-assembly process between CuX and ArS(CH₂)_mSAr ligands is hard to predict. The solid-state luminescence spectra at 298 and 77 K of 2 and 4 exhibit very strong emissions around 535 and 560 nm, respectively, whereas those for 1 and 5 display weaker ones at about 450 nm. The emission lifetimes are longer for the longer wavelength emissions (>1.0 μs arising from the cubane species) and shorter for the shorter wavelength ones (<1.4 μs arising from the rhomboid units). The Br-containing species are found to be weakly fluorescent.

Probing excited state electronic communications across diethynyl-[2.2]paracyclophane-containing conjugated organometallic polymers. Sébastien Clément, Thomas Goudreault, Diana Bellows, Daniel J. Fortin, Laurent Guyard, Michael Knorr, and Pierre D. Harvey. Chemical Communications, 2012, 48, 8640-8642. https://doi.org/10.1039/C2CC34163H

Abstract: The triplet k_ET for three organometallic polymers built upon the diethynyl[2.2]paracyclophane was studied to show good excited state electronic communication across the materials.

Intimate electronic coupling in cationic homodimeric iridium(iii) complexes. Ahmed M. Soliman, Daniel J. Fortin, Pierre D. Harvey and Eli Zysman-Colman. Dalton Transactions, 2012, 41, 9382-9393. https://doi.org/10.1039/C2DT30836C

Abstract: Herein, we report two new cationic iridium(III) homodinuclear structures linked through a diyne moiety at the 5-position of the bipyridyl ligand (1,4-di(2,2′-bipyridin-5-yl)buta-1,3-diyne) and compare these to mononuclear model systems bearing a 5-ethynyl-2,2′-bipyridine ligand. Low energy bands observed in the absorption spectra point to charge-transfer transitions for all four complexes, with these bands red-shifted in the case of the two dinuclear complexes. Electrochemical studies show metal-centred oxidation and ligand-centred first reduction potentials. In the case of the dimer bearing 2-phenylpyridine (ppyH) cyclometallating ligands, cyclic voltammetry (CV) measurements reveal two one-electron oxidation waves and a corresponding reduction in the HOMO–LUMO gap (ΔE_red-ox) compared to a mononuclear system, pointing to a significant electronic coupling between the two iridium(III) metals. The room temperature emission spectrum of this dimer is also bathochromically shifted, corroborating the CV data. In the case of the iridium dimer bearing 2-(2,4-difluorophenyl)-5-methylpyridine (dFMeppy) ligands, only a single one-electron oxidation wave is observed, but with the expected smaller ΔE_red-ox value, compared to its mononuclear counterpart. The emission spectra at room temperature are generally broad and featureless with only modest quantum efficiencies (Φ_PL = 1.4–8.4%) in 2-methyltetrahydrofuran (2-MeTHF) solution. All complexes emit at 77 K with lifetimes on the order of 4 μs. A combined density functional theory (DFT) and time-dependent DFT (TDDFT) study reveals that the emission process is best described as a mixed metal-to-ligand/ligand-to-ligand charge transfer (MLCT/LLCT).

Unexpected evolution of optical properties in Ir–Pt complexes upon repeat unit increase: towards an understanding of the photophysical behaviour of organometallic polymers. Ahmen M. Soliman, Daniel J. Fortin, Eli Zysman-Colman, and Pierre D. Harvey. Chemical Communications, 2012, 48, 6271-6273. https://doi.org/10.1039/C2CC32492J

Abstract: The photophysical properties of [Ir]-[Pt]-[Ir]-[Pt]-[Ir] ([Ir] = [Ir(ppy)₂(bpy*)]⁺ ([Pt] = trans-Pt(PBu₃)₂(CC)₂; ppyH = 2-phenylpyridine); bpy* = bipyridyl;) reveal an unprecedented triplet energy transfer from the terminal iridiums to the central Ir subunit.

Decoupling the artificial special pair to slow down the rate of singlet energy transfer. Pierre D. Harvey, Adam Langlois, Mikhail Filatov, Daniel J. Fortin, Kei Ohkubo, Sunichi Fukumi, and Roger Guilard. Journal of Porphyrins and Phthalocyanines, 2012, 16(05-06), 685-694. https://doi.org/10.1142/S1088424612500812

Abstract: Trimer 2, composed of a cofacial heterobismacrocycle, octamethyl-porphyrin zinc(II) and bisarylporphyrin zinc(II) held by an anthracenyl spacer, and a flanking acceptor, bisarylporphyrin free-base (Ar = -3,5-(tBu)₂C₆H₃), has been studied by means of absorption spectroscopy, "steady state and time-resolved fluorescence" and fs transient absorption spectroscopy, and density functional theory (DFT) in order to assess the effect of decoupling the chromophores' low energy MOs on the rate of the singlet, S₁, energy transfer, k_ET, compared to a recently reported work on a heavily coupled trimeric system, Trimer 1, [biphenylenebis(n-nonyl)porphyrin zinc(II)]-bisarylporphyrin free-base (Ar = -3,5-(tBu)₂C₆H₃). The position of the 0–0 peaks of the absorption and fluorescence spectra of Trimer 2 indicates that these porphyrin units are respectively energy donor 1, donor 2, and acceptor. The DFT computations confirm that the MOs of the cofacial donor 1-donor 2 dyad are decoupled, but significant MO coupling between donor 2 and acceptor 1 is still present despite the strong dihedral angle between their respective average planes (77.5°: geometry optimization by DFT). The fs transient absorption spectra exhibit a clear S₁–S_n fingerprint of the bisarylporphyrin zinc(II) chromophore and the kinetic trace exhibits a slow rise time of 87 ps, due to a S₁ donor 1 → donor 2 ET. The transient species donor 2 and acceptor decay respectively in the short (~1.5) ns and 6 ns time scale.

Complete Quenching of the Pd₃(dppm)₃(CO)²⁺ Cluster Emission Via Electrostatic Host–Guest Assemblies with Carboxylate-Containing Tetraphenylporphyrins of Ni(II) and Fe(III). Bin Du, Adam Langlois, Daniel J. Fortin, Christine Stern, and Pierre D. Harvey. Journal of Cluster Science, 2012, 23, 737-751. https://doi.org/10.1007/s10876-012-0470-2

Abstract: The title cluster is luminescent at 77 K and exhibits an unsaturated site for binding anions when the counter ion is PF₆⁻. A series of five non-luminescent metalloporphyrins exhibiting carboxylate anchoring groups were synthesized and characterized. These are the sodium salts of the 5-carboxyphenyl-tri-10,15,20-tolyl-, trans-di-5,10-carboxyphenyl-di-15,20-tolyl-, and tetra-5,10,15,20-carboxyphenyl(metallo)porphyrin (metallo = chloroiron(III), nickel(II)) anions. Evidence for supramolecular assemblies between the carboxylates and the cluster is provided by ³¹P NMR and UV–vis spectroscopy. The binding constant, K_1n, extracted from the UV–vis data via Benesi-Hildebrand, Scott and Scatchard plots are approximately 21,000 ± 5,000 M⁻¹ for the nickel(II) species, in agreement with the previously reported zinc(II) ones (K₁₁ = 20,000 ± 2,000 M⁻¹), but those for the chloroiron(III) are measured to be lower (12,500 ± 3,500 M⁻¹). This association is accompanied by a complete quenching of the luminescence of the cluster which can only be due to an efficient energy transfer to the d–d states of the chloroiron(III) and nickel(II) species but an electron transfer from the nickel(II)-containing chromophore to the cluster is also possible. This work demonstrates the profound effect that supramolecular interactions may have on the photophysical properties despite the long donor–acceptor separation.

Design and Photonic Properties of Novel Fluorinated Copolymers Bearing Phthalocyanine Side Groups. Guillaume Tillet, Piero De Leonardis, Ali Alaaedine, Masashi Umeda, Satoru Mori, Norio Shibata, Shawkat M. Ali, Daniel J. Fortin, Pierre D. Harvey, and Bruno Ameduri. Macromolecular Chemistry and Physics, 2012, 213(5), 1559-1568. https://doi.org/10.1002/macp.201200076

Abstract: The design and characterization of amorphous alternating copolymers endowed with a satisfactory thermal stability are reported. These alternating poly(CTFE-alt-CEVE) copolymers are synthesized by radical copolymerization of chlorotrifluoroethylene (CTFE) with 2-chloroethyl vinyl ether (CEVE), which are first modified into poly[CTFE-alt-(2-iodoethyl vinyl ether)] copolymers and then azidated in high yields. Alkynyl CF₃-containing phthalocyanines (Pcs) are then grafted via a copper-catalyzed Huisgen dipolar 1,3-addition (“grafting onto”), hence providing fluorinated copolymers with different degrees of grafting (from 10 to 72%) of Pc dangling groups. Electronic spectral (absorption, excitation, and fluorescence) and photophysical properties (fluorescence lifetimes, τ_F, and quantum yields, Φ_F) are evaluated.

B,B-Diporphyrinbenzyloxy-BODIPY Dyes: Synthesis and Antenna Effect. Bertrand Brizet, Antoine Eggenspiller, Claude P. Gros, Jean-Michel Barbe. Christine Goze, Frank Denat, and Pierre D. Harvey. The Journal of Organic Chemistry, 2012, 77(7), 3646-3650. https://doi.org/10.1021/jo3000833

Abstract:B,B-Diporphyrinbenzyloxy-BODIPY derivatives have been prepared in high yields, and the photophysical properties are reported. Singlet energy transfers from BODIPY to the porphyrin units have been analyzed.

Organometallic multiads of zinc(ii) porphyrins with interchromophoric cooperativity in S₁ and T₁ energy transfers. Bin Du and Pierre D. Harvey. Chemical Communications, 2012, 48, 2671-2673. https://doi.org/10.1039/C2CC16804A

Abstract: Three different S₁ and T₁ energy donors are linked onto a central zinc(II) porphyrin acceptor and the rates for energy transfers show evidence for cooperativity.

Photonics of a Conjugated Organometallic Pt–Ir Polymer and Its Model Compounds Exhibiting Hybrid CT Excited States. Ahmed M. Soliman, Daniel J. Fortin, Eli Zysman-Colman, and Pierre D. Harvey. Macromolecular Rapid Communications, 2012, 33(6-7), 522-527. https://doi.org/10.1002/marc.201100721

Abstract: Trans- dichlorobis(tri-n-butylphosphine)platinum(II) reacts with bis(2- phenylpyridinato)-(5,5′-diethynyl-2,2′-bipyridine)iridium(III) hexafluorophosphate to form the luminescent conjugated polymer poly[trans-[(5,5′-ethynyl-2,2′-bipyridine)bis(2- phenylpyridinato)-iridium(III)]bis(tri-n-butylphosphine)platinum(II)] hexafluorophosphate ([Pt]-[Ir])n. Gel permeation chromatography indicates a degree of polymerization of 9 inferring the presence of an oligomer. Comparison of the absorption and emission band positions and their temperature dependence, emission quantum yields, and lifetimes with those for models containing only the [Pt] or the [Ir] units indicates hybrid excited states including features from both chromophores.

Hybrid charged heterometallic Pt–Ir complexes: tailoring excited states by taking the best of both worlds. Ahmed M. Soliman, Daniel J. Fortin, Pierre D. Harvey, and Eli Zysman-Colman. Chemical Commmunications, 2012, 48, 1120-1122. https://doi.org/10.1039/C1CC15507E

Abstract: The C≡C-linkage of Pt(PR₃)₂(C≡CAr)₂ with (C⁁N)₂Ir(N⁁N)⁺ (C⁁N = 2-phenylpyridine; N⁁N = bipyridyl) leads to hetero-bi- and trimetallic species exhibiting photophysical properties reminiscent of both [Pt]- and [Ir]-containing moieties through the generation of a [Pt] → [Ir] charge transfer excited state.

Singlet and Triplet Energy Transfers in Tetra-(meso-truxene)zinc(II)- and Tetra-(meso-tritruxene)zinc(II) Porphyrin and Porphyrin-Free Base Dendrimers. Bin Du, Daniel J. Fortin, and Pierre D. Harvey. Inorganic Chemistry, 2011, 50(22), 11493-11505. https://doi.org/10.1021/ic2013667

Abstract: The synthesis, optical properties, and energy transfer features of four dendrimers composed of meso-tetrasubstituted zinc(II) porphyrin (ZnP) or a free base (P) central core, where the substituents are four truxene (Tru) or four tritruxene dendrons (TriTru), TruP, TriTruP, TruZnP, and TriTruZnP, are reported. Selective excitation of the truxene donors results in a photoinduced singlet energy transfer from the truxenes to the porphyrin acceptor. The rates for singlet energy transfer (k_ET), evaluated from the change in the fluorescence lifetime of the donors (Tru and TriTru) in the presence and absence of the acceptor (P or ZnP) for TruP, TruZnP, TriTruP, and TriTruZnP, are 5.9, 1.2, 0.87, and 0.74 (ns)⁻¹ at 298 K and 2.6, 2.6, 2.7, and 1.2 (ns)⁻¹ at 77 K, respectively. A slow triplet–triplet energy transfer from truxene to porphyrin cores in glassy 2MeTHF at 77 K is also reported with rates of 1.3 × 10³ and 0.10 × 10² s^–1 for TruZnP and TriTruZnP, respectively. If the Dexter mechanism for the triplet energy transfers is considered, these slow rates are easily explained by a poor orbital overlap between the truxene and porphyrin π systems. The fluorescence quantum yields (Φ_F) are 0.20 and 0.16 for TruP and TriTruP and 0.08 and 0.10 for TruZnP and TriTruZnP, respectively at 298 K. At 298 K, a phosphorescence from TruZnP at 795 nm was also observed and is associated with the ZnP chromophore.

Bis- and trisporphyrin bio-inspired models for bacterial antennas and photosystems. Pierre D. Harvey, Mikhail A. Filatov, and Roger Guilard. Journal of Porphyrins and Phthalocyanines, 2011, 15(11-12), 1150-1171. https://doi.org/10.1142/S1088424611004221

Abstract: This review presents the synthetic aspects and photophysical properties of trimeric systems constructed with a first unit consisting of a cofacial porphyrin and then of another porphyrin attached as a side arm. Two scenarios are dealt with. The first one is the case where the three chromophores are different, called donor 1–donor 2–acceptor, specifically where the cofacial fragment is composed of donor 1 and donor 2, and the side arm is the acceptor. They are considered as models for the apo-proteins used in the LH II (light harvesting device) in the purple photosynthetic bacteria. The second one is the case where the chromophores of the cofacial bisporphyrin residue are identical and are closely placed to each other for inter-ring π-interactions. The side arm is simply a mono-porphyrin, and therefore it is different. The cofacial bisporphyrin unit exhibits then similar characteristics to the special pairs located within the reaction center protein, and are designated as artificial special pairs. On the synthetic standpoint, the various pathways to access such models are presented fully exploiting the Suzuki methodology. On the photophysical side, a large emphasis will be placed on the singlet energy transfers. Cascade processes in the trimers donor 1–donor 2–acceptor are presented and each individual contributions donor 1 → donor 2; donor 2 → acceptor; donor → acceptor are addressed qualitatively and quantitatively. For the artificial special pairs flanked with an antenna, the effect of the spacer between the artificial special pair and the antenna will be discussed as well as the choice of substituents and metal demonstrating that one can reverse the orientation of the singlet energy transfer: artificial special pair → side arm or side arm → artificial special pair. Finally, the antenna effect are presented for one example of artificial special pair equipped with 6 semi-flexible dendritic antennas.

Design and Photophysical Properties of Zinc(II) Porphyrin-Containing Dendrons Linked to a Central Artificial Special Pair. Frédérique Brégier, Shawkat M. Aly, Claude P. Gros, Jean-Michel Barbe, Yoann Rousselin, and Pierre D. Harvey. Chemistry - A European Journal, 2011, 17(51), 14643-14662. https://doi.org/10.1002/chem.201101832

Abstract: The click chemistry synthesis and photophysical properties, notably photo-induced energy and electron transfers between the central core and the peripheral chromophores of a series of artificial special pair–dendron systems (dendron=G1, G2, G3; Gx=zinc(II) tetra-meso-arylporphyrin-containing polyimides) built upon a central core of dimethylxanthenebis(metal(II) porphyrin) (metal=zinc, copper), are reported. The dendrons act as singlet and triplet energy acceptors or donors, depending on the dendrimeric systems. The presence of the paramagnetic d⁹ copper(II) in the dendrimers promotes singlet–triplet energy transfer from the zinc(II) tetra-meso-arylporphyrin to the bis(copper(II) porphyrin) unit and slow triplet–triplet energy transfer from the central bis(copper(II) porphyrin) fragment to the peripheral zinc(II) tetra-meso-arylporphyrin. If bis(zinc(II) porphyrin) is the central core, evidence for chain folding is observed; this is unambiguously demonstrated by the presence of triplet–triplet energy transfer in the heterobimetallic systems, a process that can only occur at short distances.

Incorporation of zinc(ii) porphyrins in polyaniline in its perigraniline form leading to polymers with the lowest band gap. Simon Lamare, Shawkat M. Aly, Daniel J. Fortin, and Pierre D. Harvey. Chemical Communications, 2011, 47, 10942-10944. https://doi.org/10.1039/C1CC14026D

Abstract: Conjugated copolymers built upon quinone diimine-zinc(II) porphyrin units exhibit a very low lying charge transfer band at 800 nm and are strongly emissive from the S₂ and T₂ states.

Multinuclear Cytotoxic Metallodrugs: Physicochemical Characterization and Biological Properties of Novel Heteronuclear Gold–Titanium Complexes. Margot Wenzel, Benoît Bertrand, Marie-Joëlle Eymin, Virginie Compte, Jennifer A. Harvey, Philippe Richard, Michael Groessl, Olivier Zava, Hedi Amrouche, Pierre D. Harvey, Pierre Le Gendre, Michel Picquet, and Angela Casini. Inorganic Chemistry, 2011, 50(19), 9472-9480. https://doi.org/10.1021/ic201155y

Abstract: An unprecedented series of titanocene–gold bi- and trimetallic complexes of the general formula [[(η⁵-C₅H₅)(μ-η⁵:κ¹-C₅H₄(CH₂)_nPPh₂)TiCl₂]_mAuCl_x]^q+ (n = 0, 2, or 4; m = 1, x = 1, q = 0 or m = 2, x = 0, q = 1) have been prepared and characterized spectroscopically. The luminescence spectroscopy and photophysics of one of the compounds, [[(η⁵-C₅H₅)(μ-η⁵:κ¹-C₅H₄PPh₂)TiCl₂]₂Au]PF₆, have been investigated in 2MeTHF solution and in the solid state at 77 and 298 K. Evidence for interfragment interactions based on the comparison of electronic band positions and emission lifetimes, namely, triplet energy transfer (ET) from the Au- to the Ti-containing chromophores, is provided. The cytotoxicity of the complexes was evaluated on A2780 ovarian cancer cells and on their cisplatin-resistant cell line A2780cisR; the compounds showed activity in the low micromolar range that was markedly more active than the corresponding titanocene–phosphine precursors [(η⁵-C₅H₅)(η⁵-C₅H₄(CH₂)_nPPh₂)TiCl₂], cisplatin, and, for some of them, the gold analogue [(PPh₃)AuCl]. In an attempt to draw preliminary structure–activity relationships, cell uptake measurements and interaction studies with plasmid DNA and the model protein ubiquitin (Ub) have been undertaken on some of the compounds.

Acceleration of the through space S₁ energy transfer rates in cofacial bisporphyrin bio-inspired models by virtue of substituents effect on the Förster J integral and its implication in the antenna effect in the photosystems. Jean-Michel Camus, Shawkat M. Aly, Christine Stern, Roger Guilard, and Pierre D. Harvey. Chemical Communications, 2011, 47, 8817-8819. https://doi.org/10.1039/C1CC12839F

Abstract: The singlet k_ET for cofacial β-octaalkylporphyrin/bis(meso-aryl)porphyrin dyads increases linearly with the gap between the donor–acceptor 0–0 fluorescence peaks at 77 K.

Polyoligopeptides functionalized zinc(II)porphyrins: Step towards artificial hemes. Shawkat M. Aly, Hannah Guernon, Brigitte Guérin, and Pierre D. Harvey. Journal of Porphyrins and Phthalocyanines, 2011, 15(09-10), 871-882. https://doi.org/10.1142/S1088424611003756

Abstract: Two new zinc(II)porphyrin oligopeptides conjugates (zinc(II)-5,10,15,20-bis[4-(peptide)- phenyl]porphyrin (5) and -tetrakis[3,5-di(peptide)phenyl]porphyrin (9; peptide = -CH₂(CO)Gly-Phe-Ala-CNH₂) were prepared using the click chemistry with azides and ethynyl-containing precursors. The spectroscopic signature (S₀→S₁ and transient T₁→T_n absorption, excitation and emission spectra) are typical for zinc(II)porphyrin and shows no perturbation upon anchoring the oligopeptides, whereas some small decreases in the photophysical parameters (tau_F and Phi_F), and larger decrease in T₁ lifetimes are noted, which are attributable to the known "loose bolt" effect. The structure for 9 in solution was addressed qualitatively using computer modeling and the comparison of the bimolecular fluorescence quenching rate constants between 5 and 9 using C₆₀ as a photooxidative agent. While 5 exhibits a totally accessible zinc(II)porphyrin unit for a C₆₀ approach, 9 shows a slower quenching rate constant meaning some steric hindrance must be present.

Synthesis and Photovoltaic Properties of New Metalloporphyrin-Containing Polyplatinyne Polymers. Hongmei Zhan, Simon Lamare, Annie Ng, Tommy Kenny, Hannah Guernon, Wai-Kin Chan, Aleksandra B. Jurišić, Pierre D. Harvey, and Wai-Yeung Wong. Macromolecules, 2011, 44(13), 5155-5167. https://doi.org/10.1021/ma2006206

Abstract: Three new solution-processable platinum(II) polyyne polymers containing zinc(II) porphyrinate chromophores P1, P2, and P3 and their corresponding dinuclear model complexes were synthesized via the CuI-catalyzed dehydrohalogenation reaction of the platinum(II) chloride precursor and each of the respective bis(ethynyl)-zinc(porphyrin) metalloligands. The thermal, photophysical (absorption, excitation and emission spectra), electrochemical, and photovoltaic properties of P1–P3 were investigated. These results are also correlated by time-dependent density functional theory (TDDFT) calculations. The computations corroborate the presence of moderate conjugation in the π-systems, somewhat more accentuated for P3 where more favorable dihedral angles between the porphyrin and thiophene rings are noted. Moreover, the computed excited states are predicted to be π–π* in nature with some charge transfer components from the trans-[−C≡CPt(L)₂C≡C−]_n unit to the porphyrin rings. The optical bandgaps range from 1.93 to 2.02 eV for P1–P3. Intense π–π*-localized fluorescence emissions typical of the Q-bands of the polymers were observed. The effect of thiophene ring along the polymer chain on the extent of π-conjugation, luminescent and photovoltaic properties of these metalated materials was also examined. Bulk heterojunction solar cells using these metallopolymers as an electron donor blended with a methanofullerene electron acceptor were studied. In one case, the metallopolymer P3 showed a power conversion efficiency of 1.04% with the open-circuit voltage of 0.77 V, short-circuit current density of 3.42 mA cm^–2 and fill factor of 0.39 under illumination of an AM 1.5 solar cell simulator.

Singlet and triplet energy transfer rate acceleration by additions of clusters in supramolecular pigment-organometallic cluster assemblies. Bin Du, Christine Stern, and Pierre D. Harvey. Chemical Communications, 2011, 47, 6072-6074. https://doi.org/10.1039/C1CC11174D

Abstract: Both S₁ and T₁ energy transfer rates (porphyrin → cluster) increase from mono- to di- to tetracarboxylate[tetraphenyl-(zinc)porphyrin] adducts with [Pd₃(dppm)₃(CO)]²⁺ clusters.

A reaction-based chromogenic and fluorescent chemodosimeter for fluoride anions. Li Fu, Feng-Lei Jiang, Daniel J. Fortin, Pierre D. Harvey, and Yi Liu. Chemical Communications, 2011, 47, 5503-5505. https://doi.org/10.1039/C1CC10784D

Abstract: An innovative trihexylsilylacetylene-containing BODIPY dye was designed and proved to be a highly selective, sensitive, and fast chromogenic and fluorescent chemodosimeter for fluorides.

The First P-Stereogenic 1D Coordination Polymers with the Metal Centers in the Backbone. Christine Salomon, Daniel J. Fortin, Naïma Khiri, Sylvain Jugé, and Pierre D. Harvey. European Journal of Inorganic Chemistry, 2011, 16, 2597-2609. https://doi.org/10.1002/ejic.201100154

Abstract: The enantiomeric ligands (R,R)- and (S,S)-bis(o-anisylphenylphosphanyl)methane (R,R-22 and S,S-22) and (R,R)- and (S,S)-bis(phenyl-m-xylylphosphanyl)methane (R,R-23 and S,S-23; dppm*), were treated with [Cu(NCCH₃)₄](BF₄) and AgBF₄ to produce the binuclear complexes [Cu₂(dppm*)₂(NCCH₃)₄](BF₄)₂ or [Ag₂(dppm*)₂](BF₄)₂, respectively. Then, these complexes were used as building blocks to prepare the first P-chirogenic 1D coordination polymers {[M₂(dppm*)₂(dmb)₂](BF₄)₂}_n [dppm* = (R,R)-22, (S,S)-22, (R,R)-23, (S,S)-23, M = Cu, Ag, dmb = 1,8-diisocyano-p-menthane] where M is part of the backbone of the polymer chain. The isostructural nature of these new polymers with the achiral parent polymers, {[M₂(dppm)₂(dmb)₂](BF₄)₂}_n (M = Cu, Ag), was unambiguously demonstrated with a combination of methods including ¹H NMR, chemical analysis, UV/Vis spectrometry, emission spectroscopy and emission lifetime measurements. The structure of the bimetallic complex [Ag₂(R,R-23)₂](BF₄)₂ was solved by X-ray crystallography, and all enantiomeric complexes and polymers were characterized by circular dichroism spectroscopy.

Effect of t-BuS vs. n-BuS on the topology, Cu⋯Cu distances and luminescence properties of 2D Cu₄I₄/RS(CH₂)₄SR metal–organic frameworks. Michael Knorr, Fabrice Guyon, Marek M. Kubicki, Yoann Rousselin, Shawkat M. Aly, and Pierre D. Harvey. New Journal of Chemistry, 2011, 35, 1184-1188. https://doi.org/10.1039/C0NJ00923G

Abstract: CuI reacts with RS(CH₂)₄SR (R = n-Bu (L1); t-Bu (L2)) to afford the 2D coordination polymers [Cu₄I₄{μ-RS(CH₂)₄SR}₂]_n (R = n-Bu (1); t-Bu (2)). Their grid networks exhibit nodal Cu₄(μ₃-I)₄ clusters interconnected by dithioethers with mean Cu⋯Cu distances of 2.7265(10) and 2.911(2) Å for 1 and 2, respectively. This difference translates in a blue shift of the solid state emission bands and a decrease in emission lifetimes when trading R = n-Bu to the bulky t-Bu.

Preparation, luminescence and photoelectric properties of Langmuir–Blodgett films of alkynylplatinum(II)–zinc(II) porphyrinate/heteropolyoxometalate hybrid composites. Li Liu, Lei Hu, Hui Fu, Qiao-Min Fu, Shi Zhong Liu, Zu-Liang Du, Wai-Yeung Wong, and Pierre D. Harvey. Journal of Organometallic Chemistry, 2011, 696(6), 1319-1324. https://doi.org/10.1016/j.jorganchem.2010.12.018

Abstract: A new class of organometallic/inorganic hybrid Langmuir–Blodgett (LB) films, consisting of rigid-rod alkynylplatinum(II)–zinc(II) porphyrinate complex (OMA) as the π-conjugated donor–acceptor-type molecule and tungsto(molybdo)phosphoric heteropolyacids (HPA) (HPA = H₃PMo₁₂O₄₀ and H₃PW₁₂O₄₀, abbreviated as HPMo₁₂ and HPW₁₂, respectively) of the Keggin structure as the inorganic component, were prepared and characterized by π–A isotherms, UV–vis absorption and luminescence spectra, low-angle X-ray diffraction, scanning tunneling microscopy and surface photovoltage spectroscopy. Our experimental results indicate that stable, well-defined and well-organized Langmuir and LB films have been formed in pure water and heteropolyacid subphase. They typically have a highly organized lamellar structure in which a monolayer of HPA is most likely embedded inside the OMA molecular space formed by long chains of PBu₃. Luminescence spectra of these hybrid LB films show that HPMo₁₂ and HPW₁₂ can enhance the emission of OMA to some extent. These LB composites show good photovoltage responses and a photovoltage of 79 μV can be obtained for the OMA/HPMo₁₂ system when it is excited by light. The monolayer LB films on ITO wafer can also display interesting electrical conductivity.

Rational synthetic design of well-defined Pt(bisethynyl)/Zn(porphyrin) oligomers for potential applications in photonics. Guillaume Langlois, Shawkat M. Aly, Claude P. Gros, Jean-Michel Barbe, and Pierre D. Harvey. New Journal of Chemistry, 2011, 35, 1302-1314. https://doi.org/10.1039/C0NJ00819B

Abstract: Well-defined oligomers of 1, 2, 3 and 4 units built upon the very soluble bis-1,15-(1,4-ethynylbenzene)-3,7,13,17-tetramethyl-2,8,12,18-tetrakis(n-hexyl) zinc(II) porphyrin ligand and the trans-bis(tri-n-butylphosphine)platinum(II) linker, with acetylene or trimethylsilane as end groups, has been prepared in the presence of a dichloromethane/diethylamine mixture (1 : 1 v/v) and CuX (X = Cl, I) at room temperature, analogue to a Sonogashira coupling. The new monodisperse organometallic oligomers were characterized by ¹H, ³¹P NMR, UV-visible spectroscopies and MALDI-TOF mass spectrometry. The methyl groups placed at the 3,7,13,17-positions induces the locking of the C₆H₄ fragment in a perpendicular conformation with respect to the zinc(II) porphyrin chromophore, hence removing conjugation as corroborated by the almost total absence of spectral shift of the Soret and Q-bands upon increasing the number of units. Despite this feature, exciton coupling in the Soret band is noted at both room temperature and 77 K. The photophysical parameters, fluorescence lifetimes and quantum yields are practically constant going from the monomer, dimer and tetramer, and as a function of the monitored fluorescence wavelength, all indicating that the excitonic behavior (excitation energy delocalization) is minimal, which is consistent with the weak exciton coupling constants and the lack of conjugation of the π-system. The synthetic methodology can provide longer well-defined oligomers as the presented products were still very soluble even when the number of unit was 4.

First Halogen Anion-Bridged (MMX)_n-Type One-Dimensional Coordination Polymer Built upon d¹⁰−d¹⁰ Dimers. Tianle Zhang, Chanpeng Ji, Kaili Wang, Daniel J. Fortin, and Pierre D. Harvey. Inorganic Chemistry, 2010, 49(23), 11069-11076. https://doi.org/10.1021/ic101619y

Abstract: The complex [Ag₂(PhPPy₂)₂(NCCH₃)₂](ClO₄)₂ [PhPPy₂ = bis(2-pyridyl)phenylphosphine] reacts with NH₄Cl to form an insoluble one-dimensional polymer of the type (MMX)_n, {[Ag₂(PhPPy₂)₂Cl](ClO₄)}_n. The binuclear unit, Ag₂(PhPPy₂)₂²⁺, exhibits two PhPPy₂ tridentate ligands bridging the two Ag atoms in a head-to-tail fashion with C_2h symmetry, and the Ag···Ag distance [3.0942(11) Å, X-ray] suggests argentophilic interactions. Each Ag center adopts a distorted trigonal-bipyramidal geometry, coordinated by one P atom and two pyridyl arms at the equatorial positions and interacting with one Cl ion and one Ag ion at the axial positions. The short Ag−Cl bond length [2.5791(7) Å] indicates the presence of some covalent character. The solid-state absorption bands spread all the way to 600 nm have been interpreted by means of density functional theory (DFT) and time-dependent DFT (B3LYP), and the lowest-energy excited states are assigned to metal/halide-to-pyridyl charge transfer, consistent with the d¹⁰ electronic configuration of Ag. The calculated oscillator strengths are low because of the poor molecular orbital overlaps in the charge-transfer components. The novel material exhibits a luminescence band centered at about ∼520 nm.

Strong donor–acceptor couplings in a special pair-antenna model. Mikhail A. Filatov, Frédéric Laquai, Daniel J. Fortin, Roger Guilard, and Pierre D. Harvey. Chemical Communications, 2010, 46, 9176-9178. https://doi.org/10.1039/C0CC03665J

Abstract: A special pair model composed of two cofacial zinc porphyrins (acceptor) linked to a free base (donor) acts as an energy transfer dyad. Despite the absence of conjugation, ππ*/charge transfer excited states and ultrafast energy transfer (∼5 ps) are noted.

Synthesis, Light-Emitting, and Two-Photon Absorption Properties of Platinum-Containing Poly(arylene-ethynylene)s Linked by 1,3,4-Oxadiazole Units. Thomas Goudreault, Ze He, Yanhe Guo, Cheuk-Lam Ho, Hongmei Zhan, Qiwei Wang, Keith Yat-Fung Ho, Ka-Leung Wong, Daniel J. Fortin, Bing Yao, Zhiyuan Xie, Lixiang Wang, Wai-Ming Kwok, Pierre D. Harvey, and Wai-Yeung Wong. Macromolecules, 2010, 43(19), 7936-7949. https://doi.org/10.1021/ma1009319

Abstract: A series of soluble and thermally stable group 10 platinum(II) polyyne polymers of the type [−C≡C−Pt(PBu₃)₂−C≡C−Ar−Ox−Ar−]_n (where Ox = 1,3,4-oxadiazole; Ar = p-C₆H₄ or 2,7-dihexyl-9,9-fluorene) and [−C≡C−Pt(PBu₃)₂−C≡C−Ar−Ox−Ar−Ox−Ar−]_n (where Ar = 2,7-dihexyl-9,9-fluorene) along with their corresponding dinuclear model compounds [Ph−Pt(PEt₃)₂−C≡C−Ar−]₂−Ox− (where Ar = p-C₆H₄ or 2,7-dihexyl-9,9-fluorene) and [Ph−Pt(PEt₃)₂−C≡C−Ar−Ox−]₂−Ar− (where Ar = 2,7-dihexyl-9,9-fluorene) were prepared and characterized. The regiochemical structure of the polymers has been ascertained by single-crystal X-ray analysis on the model compound [Ph−Pt(PEt₃)₂−C≡C−p−C₆H₄−]₂−Ox−. The photophysical properties (absorption, excitation, emission, and nanosecond transient absorption spectra) of these metalated compounds in 2MeTHF at 298 and 77 K are reported. These findings are correlated by density functional theory (DFT) calculations. Geometry optimizations predict totally planar molecules for these metalated complexes and polymers, allowing better π-conjugation across the main chain. The ligands are strongly fluorescent but become also phosphorescent when the Pt atom is introduced in the backbone of the conjugated organometallic complexes and polymers. These emissions are assigned to ππ* transitions in all cases involving the Pt d_xy orbitals. These Pt compounds exhibit two-photon absorption (2PA), and their 2PA cross sections (σ₂) have been determined. The potential of exploiting such metallopolymers for the design of electrophosphorescent polymer light-emitting devices (PLEDs) and their use as single-dopant for white PLEDs have also been discussed.

The Pd₃(dppm)₃(CO)ⁿclusters (n = 1-,2-); rare cases of anionic palladium species. Sophi Dal Molin, Yves Mugnier, Daniel J. Fortin, and Pierre D. Harvey. Dalton Transactions, 2010, 39, 8976-8981. https://doi.org/10.1039/C0DT00616E

Abstract: Two novel anionic palladium clusters, Pd₃(dppm)₃(CO)ⁿ⁻ (Pd₃ⁿ; n = 1−,2−) were electrochemically generated from the dicationic cluster Pd₃²⁺ in 0.2M THF/Bu₄NPF₆via two first consecutive reversible 1-electron reductions (Pd₃²⁺ + 1 e⁻ ⇌ Pd₃⁺, −0.210, and Pd₃⁺ + 1 e⁻ ⇌ Pd₃⁰, −0.470 V vs. SCE) followed by two others at −2.350 (Pd₃⁰ + 1 e⁻ ⇌ Pd₃¹⁻, reversible) and at −2.690 V vs. SCE (Pd₃¹⁻ + 1 e⁻ ⇌ Pd₃²⁻, irreversible). The chemical stability and instability, respectively, of the Pd₃(dppm)₃(CO)ⁿ⁻ clusters (Pd₃ⁿ; n = 1−,2−) at the time scale of the electrochemical experiments were addressed by DFT computations. Indeed, geometry optimisations (B3LYP) indicate expected Pd–Pd, Pd–P, Pd–C bond length variations, but severe structure distortions are noted for the anions Pd₃¹⁻ and Pd₃²⁻, including large deviations from the planarity of the Pd₃P₆ core and for the triangular frame of the Pd₃ center. Space filling models indicate that this skeleton distortion places the phenyl-dppm groups above the unsaturated site of the M₃ frame hence protecting it from any interactions with substrates, and hence explaining the stability of the Pd₃¹⁻ species. The computed gas phase total energy shows a decrease going from Pd₃²⁺ to Pd₃¹⁺ to Pd₃⁰ and to Pd₃¹⁻, but increases going to Pd₃²⁻ hence corroborating the relative stability of these species and the observed chemical reversibility of the CV waves. Large steps in energy stabilisation going from Pd₃²⁺ to Pd₃¹⁺ to Pd₃⁰ is totally consistent with the low reduction potentials associated with these species, but the much smaller steps going from Pd₃⁰ to Pd₃¹⁻ and to Pd₃²⁻ corroborates their much larger reduction potentials. The host–guest behaviour of Pd₃¹⁻ and Pd₃²⁻ in the presence of the neutral substrate EtO₂C–CC–CO₂Et (L) and CF₃CO₂⁻ (X⁻) was examined by CV. From the shifts of the reduction waves, it was possible to demonstrate that Pd₃²⁺ and Pd₃⁺ act as host for X⁻ but not Pd₃⁰, Pd₃¹⁻ and Pd₃²⁻, whereas Pd₃²⁺, Pd₃⁺, Pd₃⁰, bind L but Pd₃¹⁻ and Pd₃²⁻ do not, corroborating evidence for stability but non-reactivity at the same time, particularly for the Pd₃¹⁻ cluster. All in all, these anionic clusters exhibit the lowest oxidation state for palladium species ever investigated.

Enantioselective Hydrogenation Catalysis Aided by a σ-Bonded Calix[4]arene to a P-Chirogenic Aminophosphane Phosphinite Rhodium Complex. Naïma Khiri, Etienne Bertrand, Marie-Jöelle Ondel-Eymin, Yoann Rousselin, Jérôme Bayardon, Pierre D. Harvey, and Sylvain Jugé. Organometallics, 2010, 29(16), 3622-3631. https://doi.org/10.1021/om100520u

Abstract: The first P-chirogenic aminophosphane−phosphinite (AMP*P) ligand (4a) supported on the upper rim of a calix[4]arene moiety was synthesized in two steps using the ephedrine methodology. Ligand 4a was used for the preparation of the corresponding rhodium complex [Rh(COD)(AMP*P)]BF₄ (5a) (COD = 1,8-cyclooctadienyl), which was tested for asymmetric catalyzed hydrogenation of various substrates. The structures of the AMP*P ligand as diborane and rhodium complexes 3a and 5a were established by X-ray analysis. The asymmetric hydrogenation catalyzed with the Rh complex 5a exhibits excellent enantioselectivities up to 98%. Investigation of modified P-chirogenic aminophosphane−phosphinite ligands 4b,c, bearing an isoelectronic or a sterically similar substituent on the P-chirogenic aminophosphane unit, demonstrates that the calix[4]arene substituent of the aminophosphane moiety plays a major role in the better asymmetric induction. The enantioselectivity of the catalyzed hydrogenation was weakly influenced by the hydrogen pressure, which is in good agreement with a stereodetermining step involving the substrate−rhodium complexes. Computer modeling indicated the presence of two conformers for the active AMP*P rhodium species, according to whether the rhodium metal is outside or inside the calix[4]arene cavity (called outer and inner). It is obvious that the complexation of the substrate with the active rhodium species forces this complex to adopt fully the outer conformation and hence explains why the calixarene fragment plays a key role in the stereodetermining step.

Reactivity of Pd₃(dppm)₃(CO)ⁿ⁺ and Pd₃(dppm)₃(CO)(RCCR)ⁿ⁺ (n = 0, +1, +2) Towards F⁻. Evidence of Reactive Intermediates and X-Ray Structure of [Pd₃(dppm)₃(MeO₂CC≡CCO₂Me)(F)]PF₆. Sophie Fournier, Cyril Cugnet, Alain Vallat, Charles H. Devillers, Yoann Rousselin, Marek M. Kubicki, Dominique Lucas, Yves Mungier, and Pierre D. Harvey. Journal of Cluster Science, 2010, 21, 837-856. https://doi.org/10.1007/s10876-010-0338-2

Abstract: The reactivity of the trinuclear palladium cluster [Pd₃(dppm)₃(CO)]ⁿ⁺ (dppm = bis(diphenylphosphinomethane); n = 2, 1) towards F⁻ was investigated by electrochemical and spectroscopic methods. The reaction depends on the charge of the cluster. The chemical reduction of the cluster dication is observed in the presence of F⁻ generating the paramagnetic monocationic cluster. Spin-trapping experiments with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) provided evidence for the radical F^• as an intermediate. In a similar manner to the dication, the monocationic cluster [Pd₃(dppm)₃(CO)]⁺ is also reduced, but in a slower process, by the F⁻ ion to produce [Pd₃(dppm)₃(CO)]⁰. Additionally, the alkyne cluster adducts [Pd₃(dppm)₃(CO)(RCCR)]ⁿ⁺ (n = 2, 1; R = CO₂Me) are also reactive towards F⁻. Particularly, the dication adduct leads to a metastable fluoride adduct [Pd₃(dppm)₃(CO)(RCCR)(F)]⁺. The electroreductive behavior of this adduct involves electron-transfer steps and F⁻ exchange equilibriums, for which digital simulation enables the extraction of the thermodynamic parameters (standard potentials and equilibrium constants). Concurrently, the monocation adduct [Pd₃(dppm)₃(CO)(RCCR)]⁺ with F⁻, leads to a disproponation generating 0.5 equiv. of [Pd₃(dppm)₃(CO)(RCCR)(F)]⁺ and 0.5 equiv. of [Pd₃(dppm)₃(CO)(RCCR)]⁰. The former slowly evolves to [Pd₃(dppm)₃(RCCR)(F)]⁺, which was described by X-ray diffraction method.

Unexpected Formation of a Doubly Bridged Cyclo-1,2-dithian 1D Coordination Cu₂I₂-Containing Luminescent Polymer. Michael Knorr, Fabrice Guyon, Abderrahim Khatyr, Magali Allain, Shawkat M. Aly, Antony Lapparand, Daniel J. Fortin, and Pierre D. Harvey. Journal of Inorganic and Organometallic Polymers and Materials, 2010, 20, 534-543. https://doi.org/10.1007/s10904-010-9389-y

Abstract: CuI reacts instantaneously with butanedithiol in MeCN solution to form a sparingly soluble and thermally stable colorless polymeric material 1 of composition [(Cu₂I₂){HS(CH₂)₄SH}]_n. Raman and IR spectroscopy confirm the presence of Cu(I) bound S–H functions. Furthermore, small amounts of the yellow compound [{Cu(μ₂-I)₂Cu}(C₄H₈S₂)₂]_n2 co-crystallize after several days. If the reaction mixture is exposed to air, polymeric 2 is isolated as the main product. An X-ray diffraction study reveals that 1D polymer 2 is assembled by rhomboid Cu(μ₂-I)₂Cu clusters (d Cu···Cu 2.6843(18) Å), which are linked through the S-atoms of six-membered 1,2-dithian heterocycles, thus generating an infinite ribbon. The low-frequency region in the Raman spectra show a striking similarity suggesting that polymers 1 and 2 bear the same cluster rhomboid Cu(μ₂-I)₂Cu clusters. The photophysics and luminescence properties of 2 have been studied experimentally and by means of DFT/TDDFT calculations.

The first unpaired electron placed inside a C₃-symmetry P-chirogenic cluster. Christine Salomon, Sophie Dal Morin, Daniel J. Fortin, Yves Mugnier, René T. Boéré, Sylvain Jugé, and Pierre D. Harvey. Dalton Transactions, 2010, 39, 10068-10075. https://doi.org/10.1039/C0DT00542H

Abstract: The Pd₃(dppm*)₃(CO)ⁿ⁺ enantiomers (n = 2 (2), 1 (3)) were prepared either from (R,R)- or (S,S)-P-chirogenic bis(phenyl-m-xylylphosphino)methane (dppm*; 1) and Pd(OAc)₂ in the presence of CF₃CO₂H, CO and water (n = 2), and then by reductive electrolysis (n = 1). The stable enantiomeric [Pd₃((S,S)-dppm*)₃(CO)]⁺˙ (3), is the first C₃-symmetry radical-cation M-M bonded cluster, therefore the odd electron is delocalized onto the Pd₃ frame within this symmetry. The novel chiral species have been characterized by circular dichroism (CD) of both enantiomers of the Pd₃(dppm*)₃(CO)²⁺ clusters (2) and by EPR spectroscopy for the Pd₃((S,S)-dppm*)₃(CO)⁺˙ paramagnetic compounds (3, g = 2.041). Evidence for reduced symmetry with respect to the achiral cluster was also obvious from the hyperfine splittings of the EPR signal which display three different hyperfine coupling values: 3 ×A(³¹P) = 83.9 × 10⁻⁴ cm⁻¹, 3 ×A(³¹P) = 69.7 × 10⁻⁴ cm⁻¹, 3 ×A(¹⁰⁵Pd) = 12.5 × 10⁻⁴ cm⁻¹. In the absence of an X-ray structure for the paramagnetic clusters, DFT computations were performed to address the geometry. The optimized geometry of the Pd₃((S,S)-dppm*)₃(CO)⁺˙ radicals (3) exhibits three phosphorus atoms placed well above the Pd₃ plane, while the three others are located below the trimetallic frame within C₃-symmetry due to intramolecular steric hindrance. This makes them chemically different with respect to the carbonyl group and explains the experimental EPR spectrum well. Consequently this C₃-symmetry deformation also induces a change in the shape of the SOMO (semi-occupied molecular orbital) towards this same symmetry compared to the corresponding achiral C_3v species.

Reactivity of CuI and CuBr toward Et₂S: a Reinvestigation on the Self-Assembly of Luminescent Copper(I) Coordination Polymers. Michael Knorr, Abdoulaye Pam, Abderrahim Khatyr, Carsten Strohmann, Marek M. Kubicki, Yoann Rousselin, Sawkat M. Aly, Daniel J. Fortin, and Pierre D. Harvey. Inorganic Chemistry, 2010, 49(13), 5834-5844. https://doi.org/10.1021/ic901906h

Abstract: CuI reacts with SEt₂ in hexane to afford the known strongly luminescent 1D coordination polymer [(Et₂S)₃{Cu₄(μ₃-I)₄}]_n (1). Its X-ray structure has been redetermined at 115, 235, and 275 K in order to address the behavior of the cluster-centered emission and is built upon Cu₄(μ₃-I)₄ cubane-like clusters as secondary building units (SBUs), which are interconnected via bridging SEt₂ ligands. However, we could not reproduce the preparation of a coordination polymer with composition [(Et₂S)₃{Cu₄(μ₃-Br)₄}]_n as reported in Inorg. Chem.1975, 14, 1667. In contrast, the autoassembly reaction of SEt₂ with CuBr results in the formation of a novel 1D coordination polymer of composition [(Cu₃Br₃)(SEt₂)₃]_n (2). The crystal structure of 2 has been solved at 115, 173, 195, and 235 K. The framework of the luminescent compound 2 consists of a corrugated array with alternating Cu(μ₂-Br)₂Cu rhomboids, which are connected through two bridging SEt₂ ligands to a tetranuclear open-cubane Cu₄Br₄ SBU, ligated on two external Cu atoms with one terminal SEt₂. The solid-state luminescence spectra of 1 and 2 exhibit intense halide-to-metal charge-transfer emissions centered at 565 and 550 nm, respectively, at 298 K. A correlation was also noted between the change in the full width at half-maximum of the emission band between 298 and 77 K and the relative flexibility of the bridging ligand. The emission properties of these materials are also rationalized by means of density functional theory (DFT) and time-dependent DFT calculations performed on 1.

Luminescent Coordination Polymers Built Upon Cu₄X₄ (X=Br,I) Clusters and Mono- and Dithioethers. Pierre D. Harvey, and Michael Knorr. Macromolecular Rapid Communications, 2010, 31(9-10), 808-826. https://doi.org/10.1002/marc.200900893

Abstract: This paper focuses on the syntheses, structures, and luminescence properties of 1D, 2D, and 3D coordination polymers built upon the tetranuclear Cu₄X₄ clusters and mono- and dithioether assembling ligands. A review of the relevant literature is presented along with our own results stressing on the salient features of the interactions between the CuI salt as the starting material and the thioethers. Among the features, the solvato- (lost or gain of a monothioether or solvent molecule) and luminescence thermochromism (temperature dependence of the emission) of the solids, and the enhanced versatility of the CuI salt to form clusters of different nuclearity (Cu₂I₂, Cu₄I₄, Cu₆I₆) and structures (closed cubane, partially open “flower-basket-like” cubane, and open cubane) upon the reaction conditions and ligands, are described. The steady state and time-resolved solid-state emission and excitation spectra (at 298 and 77 K) as well as the emission lifetimes are examined. Simple and apparently “innocent” modification may have a drastic effect on the polymer network and cluster structures, but this paper finds no obvious trend for the moment except for the ligand rigidity. The rhombic Cu₂I₂ and closed-cubane Cu₄I₄ clusters are the most encountered motifs whereas the open-flower-basket Cu₄I₄ cubane and the hexagonal Cu₆I₆ clusters are scarce.

Syntheses, Characterization, and Photophysical Properties of Conjugated Organometallic Pt-Acetylide/Zn(II) Porphyrin-Containing Oligomers. Feng-Lei Jiang, Daniel J. Fortin, and Pierre D. Harvey. Inorganic Chemistry, 2010, 49(6), 2614-2623. https://doi.org/10.1021/ic901421m

Abstract: Two conjugated organometallic oligomers of the type (−C≡CPt(L)₂C≡C(ZnP)−)_n and model compounds [PhC≡CPt(L)₂C≡C(ZnP)C≡CPt(L)₂C≡CPh] with L = tri(n-butyl)-phosphine and ZnP = zinc(II)(10,20-bis(Ar)porphyrine) (Ar = mesityl (Mes; P1 and M1) or 3,4,5-trihexadecyloxyphenyl (P2 and M2)) were synthesized and characterized (¹H and ³¹P NMR, HRMS, elemental analysis, IR, GPC, and TGA). GPC indicates that P1 and P2 exhibit respectively ∼6 and ∼3 units with a polydispersity of 1.4. M1 was also characterized by X-ray crystallography. The Pt···Pt separation in M1 is 1.61 nm, which makes P1 ∼ 9.6 nm long. The spectral measurements show that the absorption and photoluminescence spectra of M1, M2, P1, and P2 are remarkably red-shifted. For example, the low energy Q-band is observed at 677 ± 1 nm in comparison with their precursors HC≡C(ZnP)C≡CH, L1 and L2 (Ar = mesityl (Mes; L1) or 3,4,5-trihexadecyloxyphenyl (L2)), both at 298 and 77 K, for which the Q-band is observed at 622 nm. The photophysical parameters, fluorescence lifetimes (τ_F), and quantum yields (Φ_F) show a slight decrease by a factor of ∼2 (at most 3) following the trend L1 ∼ L2 > M1 ∼ M2 > P1 ∼ P2, a trend explained by a combination of the heavy atom effect and an increase in internal conversion rate due to the increase in oligomer dimension. This small variation of the photophysical data for materials of a few nm in dimension contrasts with the larger change in τ_P, phosphorescence lifetimes of the Pt-containing unit in the (−C₆H₄C≡CPt(L)₂C≡C−CC₆H₄(ZnP)−)_n oligomers with n = 3, 6, and 9 reported earlier (Liu, L.; Fortin, D.; Harvey, P. D. Inorg. Chem.2009, 48, 5891−5900). In this later case, τ_P decreased by steps of an order of magnitude as n increased from 3 to 6 to 9. This decrease was explained by a T₁ energy transfer from the Pt unit (donor) to MP (acceptor) in combination with an excitonic process (energy delocalization). Because of the full conjugation in P1 and P2, these oligomers behave as distinct molecules, and no energy transfer occurs. These properties make these materials suitable candidates for photocell applications.

Through space singlet energy transfers in light-harvesting systems and cofacial bisporphyrin dyads. PierreD.Harvey, ChristineStern, ClaudeP.Gros, and RogerGuilard. Journal of Porphyrins and Phthalocyanines, 2010, 14(01), 55-63. https://doi.org/10.1142/S1088424610001702

Abstract: Recent discoveries from our research groups on the photophysics of a few cofacial bisporphyrin dyads for through space singlet and triplet energy transfers raised several important investigations about the mechanism of energy transfers and energy migration in light-harvesting devices, notably LH II, in the heavily investigated purple photosynthetic bacteria. The key feature is that for face-to-face and slipped dyads with controlled structure using rigid spacers or spacers with limited flexibilities, our fastest rates for singlet energy transfer are in the 10 × 10⁹s^-1 (i.e. 100 ps time scale) for donor-acceptor distances of ~3.5–3.6 Å. The time scale for energy transfers between different bacteriochlorophylls, notably B800*→B850, is in the ps despite the long Mg⋯Mg separation (~18 Å). This short rate drastically contrasts with the well-accepted Förster theory. This review focuses on the photophysical processes and dynamics in LH II and compares these parameters with our investigated model dyads build upon octa-etio-porphyrin chromophores and rigid and semi-rigid spacers. The recently discovered role of the rhodopin glucoside (carotenoid) will be analyzed as possible relay for energy transfers, including the possibility of uphill processes at room temperature. In this context the concept of energy migration may be complemented by parallel relays and uphill processes. It is also becoming more obvious that the irreversible electron transfer at the reaction center (electron transfer from the special pair to the phaeophytin) renders the rates for energy transfer and migration faster precluding all possibility of back transfers.

Through-Bond versus Through-Space T₁ Energy Transfers in Organometallic Compound−Metalloporphyrin Pigments. Diana Bellows, Thomas Goudreault, Shawkat M. Aly, Daniel J. Fortin, Claude P. Gros, Jean-Michel Barbe, and Pierre D. Harvey. Organometallics, 2009, 29(2), 317-325. https://doi.org/10.1021/om900584n

Abstract: The preparation and characterization of two d⁹−d⁹ M₂-bonded Pt₂(dppm)₂(C≡CC₆H₄-M(P))₂ complexes (where M = Zn or Pd, and P = diethylhexamethylporphyrin) were achieved. The central [Pt₂(dppm)₂(C≡CC₆H₄)₂] organometallic unit appears to be an independent chromophore and is suspected to be luminescent at 77 K (in 2MeTHF) in the porphyrin-containing complexes, as this is the case for the unfunctionalized Pt₂(dppm)₂(C≡CPh)₂ parent compound. However, when this spacer is connected (by a single C−C bond) to either M(P) (M = Zn, Pd), even in the absence of conjugation (as the computed dihedral angle between the C₆H₄ and porphyrin planes is ∼84.5°), total quenching of the luminescence of the [Pt₂(dppm)₂(C≡CC₆H₄)₂] central unit is observed. Only T₁−T_n absorption bands of the metalloporphyrins are observed in the nanosecond transient absorption spectra, indicating the absence of a charge-separated state in these systems, thus indicating the presence of T₁ species only. Consequently, efficient T₁ energy transfers from [Pt₂(dppm)₂(C≡CC₆H₄)₂] donor to the M(P) acceptor occur. Using a lower limit of measurable value of Φ_e < 0.0001, the rate for T₁ energy transfers is estimated to be >10⁸ s⁻¹. This rate indicates a fast process, which is 4 orders of magnitude larger than as recently reported in electrostatically held dyads between the unsaturated clusters M₃(dppm)₃(CO)²⁺ (M = Pd, Pt) and metalloporphyrins (M′(TPP-CO₂⁻); M′ = Zn, Pd; TPP = tetraphenylporphyrin) as the donor and acceptor, respectively (Aly, S. M.; Ayed, C.; Stern, C.; Guilard, R.; Abd-El-Aziz, A. S.; Harvey, P. D. Inorg. Chem., 2008, 47, 9930−9940). In the latter cases, the through-space T₁ energy transfer rates were on the order of 10⁴ s⁻¹.

Recent Progress on the Photonic Properties of Conjugated Organometallic Polymers Built Upon the trans-Bis(para-ethynylbenzene)bis(phosphine)platinum(II) Chromophore and Related Derivatives. Wai-Yeung Wong, and Pierre D. Harvey. Macromolecular Rapid Communications, 2010, 31(8), 671-713. https://doi.org/10.1002/marc.200900690

Abstract: This review article surveys the electronic and photophysical properties of conjugated organometallic polymers built upon the title compound and its related derivatives focussing primarily on systems investigated in our laboratories. The general structure of the polymers is (trans-bis(para-ethynylbenzene)bis(phosphine)platinum(II)-G)_n where G is a conjugated group such as thiophene, fluorene, carbazole, substituted silole, quinone derivative, and metalloporphyrin residue, or a non-conjugated main-group moiety. Systems based on substituted phenylene units and other related fused rings are also discussed. The phosphine ligands are generally triethyl- or tri-n-butylphosphine groups. These trans-platinum(II) polymers and the corresponding model compounds are compared to the corresponding ortho-derivatives in the quinone series, and the newly prepared paracyclophane-containing polymers. For the porphyrin series, a comparison of fully conjugated oligomers exhibiting the general structure (trans-bis(para-ethynyl(zinc(porphyrin)))bis(phosphine)platinum(II))_n (i.e., the C₆H₄ group is absent from the main chain) will be made. This contribution also includes a description of the properties of the mononuclear chromophore itself, properties that define those of the polymers. Potential applications with regard to electronic and optical devices will be highlighted. These soluble and stable materials feature both the processing advantages of polymers and the functionality provided by the presence of metal centers. These multifunctional organometallic polyyne polymers exhibit convenient structural variability as well as optical and electronic properties, which renders them important for use in different research domains as chemical sensors and sensor protectors, as converters for light/electricity signals, and as patternable precursors to magnetic metal alloy nanoparticles.

Selective Stepwise Suzuki Cross-Coupling Reaction for the Modelling of Photosynthetic Donor−Acceptor Systems. Mikhail A. Filatov, Roger Guilard, Pierre D. Harvey. Organic Letters, 2010, 12(1), 196-199. https://doi.org/10.1021/ol902614k

Abstract: A Suzuki reaction performed as a selective stepwise substitution of two boryl groups on a diarylporphyrin precursor is reported for straightforward construction of a porphyrin trimer, modeling photosynthetic donor−acceptor systems.

Homo- and Co-Polymers of Norbornene Containing Aryl- and Hetaryl-Azo Dyes; Synthesis and Sensing Properties. Alaa Abd-El-Aziz, Patrick O. Shipman, Paul R. Shipley, Britta N. Boden, Shawkat M. Aly and Pierre D. Harvey. Macromolecular Chemistry and Physics, 2009, 210(24), 2099-2106. https://doi.org/10.1002/macp.200900350

Abstract: A series of polynorbornene homo- and copolymers containing aryl- and/or hetaryl-azo dyes were prepared through ring-opening metathesis polymerization (ROMP). Thermal studies indicated that the polymers were thermally stable up to 250 °C, and possessed glass transition temperatures ranging from 93 to 133 °C. In THF solutions, the aryl-azo dye containing homopolymers, displayed λ_max = 417 nm while the hetaryl-azo dye containing homopolymers displayed λ_max = 495 nm. The copolymers displayed a λ_max that encompassed both the aryl- and hetaryl-azo dye range. The monomers and polymers showed bathochromic shifts in solution when acidified. The polymers were cast into films that changed colour in the presence of both aqueous 1.2 M HCl or HCl_(g). The colour change reverses when exposed to aqueous 1.2 M NaOH or NH_3(g). This process was repeated several times without disintegration of the polymer film, indicating that these polymers may be useful as reusable acid sensors.

Efficient Electrophosphorescence from a Platinum Metallopolyyne Featuring a 2,7-Carbazole Chromophore. Cheuk-Lam Ho, Chung-Hin Chui, Wai-Yeung Wong, Shawkat M. Aly, Daniel Fortin, Pierre D. Harvey, Bing Yao, Zhiyuan Xie and Lixang Wang. Macromolecular Chemistry and Physics, 2009, 210(21), 1786-1798. https://doi.org/10.1002/macp.200900351

Abstract: The synthesis, thermal and emission properties of an electrophosphorescent platinum(II) metallopolyyne polymer consisting of 9-butylcarbazole-2,7-diyl spacer P1 are described. The optical and electronic properties of P1 are compared to their molecular diplatinum(II) and digold(I) model complexes. The photophysical properties of P1 are somehow analogous to its 2,7-fluorene-linked congener but differs significantly from that for the 3,6-carbazole derivative. Its optical band gap is notably reduced as compared to that for the 3,6-carbazole analog. Multi-layer polymer light-emitting diodes (PLEDs) were fabricated with P1 as the emitting layer which gave a strong green-yellow electrophosphorescence. The best PLED can reach the maximum current efficiency of 4.7 cd · A⁻¹ at 5 wt.-% doping level, corresponding to an external quantum efficiency of 1.5%. This represents the first literature example of efficient PLEDs exhibiting pure triplet emission under electrical excitation for metallopolyynes without the concomitant singlet emission. For safety concern, this metallopolymer was also tested for possible cytotoxicity and it does not show significant cytotoxic activity on liver and breast derived human cells at reasonable doses, rendering this functional material safe to use in practical devices.

Intrachain Electron and Energy Transfers in Metal Diynes and Polyynes of Group 10−11 Transition Elements Containing Various Carbazole and Fluorene Hybrids. Shawkat M. Aly, Cheuk-Lam-Ho, Wai-Yeung Wong, Daniel Fortin and Pierre D. Harvey. Macromolecules, 2009, 42(18), 6902-6916.https://doi.org/10.1021/ma9013077

Abstract: A series of soluble and thermally stable group 10 platinum(II) polyyne polymers of the type [−C≡C−Pt(PBu₃)₂−C≡C−X−]_n along with their corresponding dinuclear model compounds [Ph−Pt(PEt₃)₂−C≡C]₂−X− and [Ph₃P−Au−C≡C]₂−X− where X = F, Cz′, Cz, Cz−F, (Cz)₂, (Cz)₃ and Cz−F−Cz; F = 2,7-fluorene, Cz′ = 2,7-carbazole, Cz = 3,6-carbazole, were prepared and characterized. The electronic spectra (absorption, excitation, emission and ns transient absorption spectra) and the photophysical properties of these metalated compounds in 2MeTHF at 298 and 77 K are reported. These findings are correlated to the computational data obtained by density functional theory (DFT). Evidence for intramolecular singlet electron and triplet energy transfers from the Cz chromophore to the F moiety is provided and discussed in detail for those with organic spacers consisting of the carbazole−fluorene hybrids. The rate for electron transfer is very rapid (k_et > 4 × 10¹¹ s⁻¹ at 298 K) whereas that for triplet−triplet energy transfer is much slower (k_ET ∼ ca. 10³ s⁻¹ time scale). The k_ET values for the digold dyads are lower than that found for the diplatinum analogues, which are slower than the corresponding platinum-containing polymers. The observed increase in k_ET for the dinuclear systems is explained by the triplet excited state population of the diplatinum species as compared to the digold congener, and for the polymers, the larger rates (twice as fast) are due to the presence of two fluorene chromophores flanking the carbazole-containing unit, hence providing two pathways to relaxation.

Energy Transfers in Monomers, Dimers, and Trimers of Zinc(II) and Palladium(II) Porphyrins Bridged by Rigid Pt-Containing Conjugated Organometallic Spacers. Diana Bellows, Shawkat M. Aly, Claude P. Gros, Maya El Ojami, Jean-Michel Barbe, Roger Guilard and Pierre D. Harvey. Inorganic Chemistry, 2009, 48(16),l 7613-7629. https://doi.org/10.1021/ic900840w

Abstract: A series of linear monomers (spacer−M(P)), dimers (M(P)−spacer−M′(P)), and trimers (M(P)−spacer−M′(P)−spacer−M(P)) of spacer/metalloporphyrin systems (M′ = Zn, M = Zn, Pd, P = porphyrin, and spacer = trans-C₆H₄C≡CPtL₂C≡CC₆H₄- (L = PEt₃)) including mixed metalloporphyrin compounds, were synthesized and characterized. The S₁ and T₁ energy transfers Pd(P)*→Zn(P) occur with rates of ∼2 × 10⁹ s⁻¹, S₁, and 0.15 × 10³ (slow component) and 4.3 × 10³ s⁻¹ (fast component), T₁. On the basis of a literature comparison with a related dyad, the Pt atom in the conjugated chain slows down the transfers. The excitation in the absorption band of the trans-C₆H₄C≡CPtL₂C≡CC₆H₄- spacer in the 300−360 nm range also leads to T₁ energy transfer (spacer* → M(P); M = Zn, Pd) with rates of 10⁴ s⁻¹.
 

Nanometer Length-Dependent Triplet−Triplet Energy Transfers in Zinc(II)Porphyrin/trans-Bis(ethynylbenzene)Platinum(II) Oligomers. Li Liu, Daniel Fortin and Pierre D. Harvey. Inorganic Chemistry, 2009, 48(13), 5891-5900. https://doi.org/10.1021/ic900198h

Abstract: The synthesis and characterization of organometallic oligomers of the type [(p-C₆H₄)C≡CPt(P(n-Bu)₃)₂C≡C(p-C₆H₄)Zn(P)]_n with the corresponding models [(C₆H₅C≡C)Pt(P(n-Bu)₃)₂C≡C(p-C₆H₄)Zn(P)(p-C₆H₄)C≡CPt(P(n-Bu)₃)₂(C≡CC₆H₅)], where Zn(P) is zinc(II)-10,20-di(mesityl)- (n = 4, 9) or zinc(II)-10,20-di-n-pentyl-porphyrin (n = 3, 6, 9), are reported. The electronic spectra (absorption, excitation, emission, and transient absorption) and the photophysical properties (emission lifetimes and quantum yields) of these species in 2-methyltetrahyrofuran at 298 and 77 K are presented. Rates for triplet (T₁) energy transfer, k_ET, from the [(p-C₆H₄C≡C)Pt(P(n-Bu)₃)₂(C≡C-p-C₆H₄)] spacer to Zn(P) vary from 2.4 × 10⁴ to 1.3 × 10⁶ s⁻¹. For the n-pentyl case, a rate dependence of oligomer size is noted as k_ET increases with the number of units, n. This phenomenon is interpreted by the presence of an excitonic process (i.e., delocalization of the energy along the Zn(P) array).

A-Frame-Containing Organometallic Oligomers Constructed From Homo- and Heterobimetallic M(μ-dppm)₂M′ (M/M′ = Pd, Pt) Building Blocks. Sébastien Clément, Shawkat M. Aly, Jérôme Husson, Daniel Fortin, Carsten Strohmann, Michael Knorr, Laurent Guyard, Alaa S. Abd-El-Aziz and Pierre D. Harvey. European Journal of Inorganic Chemistry, 2009, 2009(17), 2536-2546. https://doi.org/10.1002/ejic.200900103

Abstract: The homo- and heterodinuclear complexes XM(μ-dppm)₂M′X (M = M′ = Pd, X = Cl 1a; M = M′ = Pd, X = I 1b; M = Pd, M′ = Pt, X = Cl 2a; M = Pd, M′ = Pt, X = I 2b; M = M′ = Pt, X = Cl 3a; M = M′ = Pt, X = I 3b) react with the diisocyanide ligand 1,2-bis(2-isocyanophenoxy)ethane (diNC) or the more soluble 1,2-bis(2-isocyano-4-tert-butylphenoxy)ethane (tBudiNC) in a 1:1 ratio to provide the thermally stable polymeric materials 4–9 {[XM(μ-dppm)₂M′(μ-CN-C₆H₃R-2-OCH₂CH₂O-2-C₆H₃R-NC)]X}_n (M = M′ = Pd, R = H, X = Cl 4a, I 4b; R = tBu, X = Cl 7; M = M′ = Pt, R = H, X = Cl 5a, I 5b; R = tBu, X = Cl 8; M = Pd, M′ = Pt, R = H, X = Cl 6a, I 6b; R = tBu, X = Cl 9). These A-frame-containing materials have been characterized in solution or in the solid state by ³¹P NMR (MAS) spectroscopy, elemental analysis, MALDI-TOF, DSC, TGA, IR and T₁/NOE [³¹P NMR spin-lattice relaxation time and nuclear Overhauser enhancement constant (NOE) measurements]. The IR, Raman [ν(CN) bridging vs. terminal] and NMR spectroscopic data reveal the presence of an A-frame structure for these new materials. Evidence of an oligomer (including at least two units, determined by T₁/NOE experiments) – polymer equilibrium in solution was obtained at room temperature. These polymers are luminescent (phosphorescence) at 77 K in solution and in the solid state, exhibiting broad emission bands in the 500–800 nm range. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The First C₃-Symmetric P-Stereogenic Diphosphinomethane Trinuclear Palladium Clusters: Synthesis and Characterization. Christine Salomon, Daniel Fortin, Christophe Darcel, Sylvain Jugé and Pierre D. Harvey. Journal of Cluster Science, 2009, 20(1), 267-280. doi.org/10.1007/s10876-009-0244-7

This paper is dedicated to Professor C.N.R. Rao.

Abstract: The enantiomeric ligands (R,R)- and (S,S)-bis(o-anisylphenylphosphino)methane (R,R-14 and S,S-14, respectively) were used to prepare the C₃-point group clusters [Pd₃(dppm*)₃(CO)(O₂CCF₃)](CF₃CO₂) with dppm* = (R,R)-14 or (S,S)-14. The chiral structure of an enantiomeric clusters (with the chiral R,R-ligand (R,R)-14) was unambiguously demonstrated by both X-ray structure determination and by circular dichroism spectroscopy.

Symmetric Heteropolynuclear Ti(IV)/Cu(I) Complexes Exhibiting Stepwise Electrochemical Reductions to Ti(III) Species. Pierre Le Gendre, Virginie Comte, Marie-Joëlle Odel-Eymin, Claude Moïse, Eveline Pousson, Philippe Richard, Yves Mugnier, Daniel Fortin, René T. Boeré and Pierre D. Harvey. Inorganic Chemistry, 2009, 48(7), 3095-3103. https://doi.org/10.1021/ic8023869

Abstract: The heterotrinuclear complexes, [(CpTiCl₂Cp-PPh₂)₂Cu]⁺ (2) (as PF₆⁻ salt) and [CpTiCl₂Cp-PPh₂]₂CuCl (3), containing two electron-poor Ti(IV) fragments and one electron-rich Cu(I) center, and a tetrametallic species, [(CpTiCl₂Cp-PPh₂)Cu(μ-Cl)]₂ (4), were synthesized and characterized. The trinuclear nature of 2 and 3 was demonstrated by X-ray crystallography for which the three metallic centers are held together by two CpPPh₂ ligands. Weak Cl···Cu interactions are noted in 3, whereas two stronger Cl−Cu bridges are depicted in the cationic complex 2. The tetranuclear complex 4 contains two Cu atoms bridged together by two chloride ligands and connected to one Ti atom by one CpPPh₂ ligand and one μ-Cl ligand. Despite the short distances in the Ti−Cl−Cu bridges, notably in 2 and 4, the NMR spectra reveals evidence of fluxion in solution attributed to the lability of the μ-Cl ligands. Electrochemical experiments performed on 2 (rotating disk electrode and cyclic voltammograms) demonstrated the presences of two successive 1-electron reductions generating a first structurally unsymmetrical paramagnetic species [(CpTiCl₂Cp-PPh₂)₂Cu]⁰ (2′), confidently characterized by electron paramagnetic resonance (EPR) as a Ti(III)−Cu(I)−Ti(IV) system, and a second one, which is tentatively assigned to a symmetric neutral complex formulated as [CpTiClCp-PPh₂]₂CuCl (5) with an EPR signature indistinguishable from that of 2′ (i.e., Ti(III)−Cu(I)−Ti(III) system with a similar electronic environment). Density functional theory (DFT) computations examining the nature of the frontier orbitals and the geometry confirmed the presence and lack of symmetry in 2 and 2′, respectively. The detection of chemical/electrochemical mechanisms in the electrochemical studies provides a clear explanation for the stepwise reduction behavior in these systems through chloride ligand transfer from Ti to Cu prior to the first reduction step. This transfer process is fully reversible upon re-oxidation. The electrochemical properties of complexes 3 and 4 are also reported.