Heteroleptic diimine copper(i) complexes with large extinction coefficients: synthesis, quantum chemistry calculations and physico-chemical properties.

International audience: Using the HETPHEN approach, five new heteroleptic copper(i) complexes composed of a push-pull 4,4'-styryl-6,6'-dimethyl-2,2'-bipyridine ligand and a bulky bis[(2-diphenylphosphino)phenyl]-ether (DPEphos) or a bis2,9-mesityl phenanthroline (Mes2Phen) were prepared and characterized by electronic absorption spectroscopy, electrochemistry, and TD-DFT calculations. These complexes exhibit very intense absorption bands in the visible region with extinction coefficient in the range of 5-7 × 10(4) M(-1) cm(-1). The analysis of the position, intensity and band shape indicates a strong contribution from an intra-ligand charge-transfer transition centered on the styrylbipyridine ligand along with MLCT transitions. These new complexes experimentally demonstrate that good light harvesting properties with bis-diimine copper(i) complexes are a reality if one chooses suitable ligands in the coordination sphere. This constitutes a milestone towards using bis-diimine copper(i) complexes for solar energy conversion (artificial photosynthesis and solar cells)

Synthesis and characterization of polymers for nonlinear optical applications

International audienceA difunctional NLO Azo-Dye chromophore has been synthesized and polymerization has been performed with a comonomer bearing a side-chain epoxy group. Deposition of the polymer on glass substrates was performed by spin-coating, resulting in uniform films up to 2 µm thickness. The orientation of the chromophore was performed under a " pin-to-plane " positive corona discharge followed by a heat-treatment in order to obtain reticulation of the films. Molecular orientation has been investigated using UV-Vis. and Raman spectroscopy. Poling of the films results in a decay of absorbency as well as in a blue shift of the spectrum. At the same time, the 1600 cm-1 band disappears from the Raman spectra, indicating orientation of the chromophores. Cross-linking has been studied by FTIR and all-optical poling and showed an improved stability of the electro-optic thin films

Synthèse et étude de systèmes moléculaires sensibilisateur-connecteur-accepteur pour la séparation photoinduite de charges en vue de la photosynthèse artificielle

Les propriétés spécifiques recherchées dans les molécules préparées dans ce travail sont d une part la photoproduction d un fort oxydant ou d un fort réducteur et d autre part le transfert d électron photocumulatif (bis-oxydation d un donneur d électron suite à l absorption successive de plusieurs photons). La première partie concerne le synthèse de dyades comportant un complexe de ruthénium trisbipyridine relié à une molécule de fullerène ou un naphtalène bisimide par un connecteur oligo(phénylèneéthynylène). Dans une seconde partie, un pérylène monoimide a été connecté à un tétrathiafulvalène étendu (TTFex). Dans la troisième partie, un complexe de ruthénium a été fonctionnalisé par un TTFex. L excitation lumineuse de cette dernière molécule, chimisorbée à la surface de TiO2, devrait permettre d observer le transfert d électron photocumulatifThe molecules developed in this project were designed in order to photogenerate either a strong oxidant or a strong redactor or to mimic the photocumulative electron transfer (bis-oxidation of an electron donor upon stepwise absorption of several photons). The first part concerns the synthesis of dyads containing a ruthenium trisbipyridine complex connected to either a fullerene or to a naphthalene bisimide via an oligo(phenyleneethynylene spacer). In the second part, a perylene monoimide was connected to an extended TTF (TTFex). In the third part, a polypyridine ruthenium complex was functionalized by a TTFex. Light excitation of the latter dyad, chemisorbed on TiO2 surface, should result in a photocumulative electron transferNANTES-BU Sciences (441092104) / SudocSudocFranceF

Synthèse et caractérisation d édifices moléculaires pour la séparation et l accumulation de charges photo-induites

La synthèse ainsi que les caractérisations physicochimiques et photophysiques d'architectures moléculaires pour mimer le processus de la photosynthèse ont été réalisées au cours de ce travail de thèse. Les édifices synthétisés reposent sur un jeu de donneurs d'électrons (ferrocène, polyarylamine ,porphyrine de zinc, phtalocyanine de zinc, tétrathiafulvalène étendu, complexe polypyridinique de ruthénium) et d'accepteurs d'électrons (pérylène monoimide, fullerène C60, naphtalène bisimide, porphyrine d'or). Ces unités redox et/ou photoactives sont reliées entre elles par des interactions supramoléculaires ou par des liaisons covalentes. Un intérêt particulier a été porté sur l'étude de l'influence du connecteur sur la vitesse du transfert de charges. Parmi les différents types de connecteurs nous avons utilisé l'oligophenylèneétynylène, qui induit une excellente communication électronique et le triazole obtenu par click chemitry qui s'avère moins favorable au transfert d'électron. La fonction de transfert d'électron photo-accumulatif à également été atteinte grâce à une dyade composée d'un complexe de ruthénium polypyridine relié à une polyaminearomatique. La dyade a été greffée à la surface d'un semi-conductor (TiO2) et a permis, pour la première, fois d'observer un double transfert d'électron photoinduit, suite à deux excitations lumineuses consécutives et sans avoir recours à un donneur d'électron sacrificiel.During this thesis project different molecular architectures were synthesized and studied to mimic the process of natural photosynthesis. The synthesis and physico-chemical and photo-physical characterizations of the new molecular architectures were performed. The different molecules were composed of an electron donor (ferrocene, polyarylamine, zinc porphyrin, zinc phthalocyanine, extended tetrathiafulvalene, and ruthenium polypyridine complex) and an electron acceptor (perylene monoimide, fullerene C60, naphthalene bisimide, gold porphyrin). These redox and/or photoactive units were linked by supramolecular interactions or by covalent bonds. A special interest was devoted to the influence of this linker on the electron transfer rate. Oligophenyleethynylene bridges enable an excellent electronic communication, whereas the triazole moiety, formed by click chemistry, exhibits lower electronic coupling. A photo-accumulative electron transfer function was also achieved with a dyad composed of a ruthenium complex sensitizer and a polyarylamine electron donor. The dyad was chemisorbed on a semi-conducteur surface (TiO2) and, for the first time, a double photoinduced electron transfer upon two successives excitations was demonstrated without the use of a sacrificial electron donor.NANTES-BU Sciences (441092104) / SudocSudocFranceF

A cheap and efficient method for selective para-iodination of aniline derivatives

International audienc

Supramolecular light harvesting antennas to enhance absorption cross-section in dye-sensitized solar cells

Doping a zinc porphyrin based-sensitizer with antenna molecules, axially held by metallo-supramolecular interactions, enhances the light-harvesting efficiency and the overall photo-conversion efficiency of the solar cells by about 30%

Solid-state dye-sensitized TiO(2) solar cells based on a sensitizer covalently wired to a hole conducting polymer

We report on the molecular wiring efficiency of a ruthenium polypyridine complex acting as a sensitizer connected to a poly(3-hexyl) thiophene chain acting as hole transporting material. We have developed an efficient synthetic strategy to covalently connect via an ethanyl spacer a regioregular poly(3-hexyl) thiophene chain to a ruthenium complex. Solid-state dye-sensitized solar cells were prepared either with the latter system or with a similar ruthenium sensitizer but lacking the polymer chain (reference system). The comparison of the photocurrent-photovoltage characteristics of the cells recorded under AM1.5 indicates a two fold improvement of the overall photoconversion efficiencies when the sensitizer is grafted to the hole transporting material (eta = 0.27%) relative to the reference system (eta = 0.13%). The higher photovoltaic performance can be attributed to the better diffusion-like propagation of the holes from the sensitizer to the counter electrode through the covalently linked polythiophene chain

Study of the cross-linking mechanism of a copolymer containing an electrooptic chromophore

9 pagesThe mechanism of the cross-linking reaction occuring between an NLO chromophore copolymerized with a glycidyl epoxide unit (polymer PIII) was rationalized using magic angle spinning (MAS) NMR spectroscopy. A first study conducted on a system composed of a model chromophore and a simple epoxy molecule enabled us to attribute the NMR changes that accompany the epoxy ring opening. Further, the use of a guest-host system made of an azo chromophore dispersed in an MMA-GMA copolymer matrix indicated a quantitative yield of the carboxyl/epoxy anchorage reaction after 30 min of heating at 140°C. The 13C cross polarization (CP)/MAS NMR spectroscopic study showed unambiguously that the cross-linking reaction in polymer PIII is due to a nucleophilic opening of the epoxy rings by the carboxylic groups of the chromophores resulting in carboxylic ester bond formation. Finally, the blue shift of the ca 500 nm absorption band was modeled with a computational study. It is concluded that the esterification of the acid carboxylic group of the chromophore causes the torsion of the azo molecule

Synthesis of new crosslinkable co-polymers containing a push–pull zinc porphyrin for non-linear optical applications

International audienceIn this paper, the synthesis of a crosslinkable co-polymer containing new push–pull arylethynyl zinc porphyrins is described. The synthesis of porphyrin chromophores, analogous to Therien's porphyrin (J. Am. Chem. Soc. 1996, 118, 1497–1503) functionalized with a methacrylic polymerizable group and a carboxylic acid crosslinking group was achieved with a new synthetic procedure leading to a higher overall yield compared to what was previously reported in the literature for similar and simpler structures. Radical copolymerization of the porphyrin chromophore with glycidyl methacrylate has then been carried out with success. This work opens a perspective on the possibility to integrate porphyrinic chromophore with high first-order molecular quadratic hyperpolarizability coefficient in opto-electronic devices.This work describes an efficient synthetic route to prepare a methacrylate co-polymer containing push–pull zinc porphyrin and glycidyl units