Perfluorocyclohexene bridges in inverse DiArylEthenes: synthesis through Pd-catalysed C-H bond activation, experimental and theoretical studies on their photoreactivity.

International audienceThe palladium-catalysed direct di-heteroarylation of 1,2-dichloroperfluorocyclohexene with a variety of heteroarenes gives rise in to a new family of 1,2-di(heteroaryl)perfluorocyclohexenes. These derivatives do not exhibit photoreactivity and this unexpected outcome is explained by calculations demonstrating the lack of reactive isomers

Sequential double second-order nonlinear optical switch by an acido-triggered photochromic cyclometallated platinum(ii) complex.

International audienceAn unprecedented DTE-based Pt(II) complex, 2(o), which stands as the first example of a sequential double nonlinear optical switch, induced first by protonation and next upon irradiation with UV light is presented

Photoswitching of the second-order nonlinearity of a tetrahedral octupolar multi DTE-based copper(I) complex.

International audienceThe modulation of the quadratic NLO response of an octupolar metal-based chromophore featuring four photochromic dithienylethene units is reported. Quantum mechanical simulations are consistent with a full switching of the DTE units and reproduce the strong enhancement of the NLO response

Tunable double photochromism of a family of bis-DTE bipyridine ligands and their dipolar Zn complexes.

International audienceThe photoinduced ring-closure/ring-opening reactions of a series of bis-dithienylethene derivatives, as free ligands and Zn(II)-complexes, are investigated by resorting to theoretical (time-dependent density functional theory) and kinetic analyses in solution. The originality of the system stems from the tunability of the photoreaction quantum yields and conversion yields as a function of the electronic structure. The latter could be varied by modifying the electron-donating character of the DTE-end substituents L(a-d) (o,o) (a, D = H; b, D = OMe; c, D = NMe(2); d, D = NBu(2)) and/or the Lewis character of the metal ion center L(a-d)ZnX(2) (o,o) (L(a-c), X = OAc; L(d), X = Cl). The orbital description of the doubly-open form (o,o) and half-closed form (o,c) predicts that double closure to the form (c,c) would occur using UV irradiation. Photokinetic studies on the complete series demonstrate that photocyclization proceeds following a sequential ring closure mechanism. They clearly point out distinct quantum yields for the first and second ring closures, the latter being characterized by a significantly lower value. Dramatic decrease in both the quantum yields of the ring-closure and ring-opening processes is demonstrated for the complex L(d)ZnCl(2) exhibiting the strongest charge-transfer character in the series investigated. These studies show that this series of DTE derivatives provides an efficient strategy to tune the photochromic properties through the combination of the electron-donor and electron-acceptor (D-A) groups

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

Direct Arylation of Dithienylperfluorocyclopentenes via Palladium-Catalysed C-H bond Activation: A Simpler Access to Photoswitches

International audienceThe palladium-catalysed direct arylation of dithienylperfluorocyclopentene (DTE) derivatives proceeds in moderate to high yields with a variety of aryl bromides in the presence of 5 mol% Pd(OAc)2/dppb as the catalyst, and KOAc as the base. The use of cyclopentyl methyl ether as the solvent was found to be crucial to avoid the decomposition of the reactants and products. The reaction proceeds regioselectively at C5 of thiophenes, and tolerates various substituents such as formyl, acetyl, ester, nitrile or nitro on the aryl bromide. Therefore, this method allows a straightforward modulation of the electron density distribution on DTE derivatives

Structure–property relationships in normal and mixed dithienylethenes – polyoxometalates supramolecular assemblies with fast solid-state photochromic properties

International audienceFive new highly photochromic hybrid organic-inorganic materials were successfully prepared by supramolecular assembly of normal (1+) and mixed (2+) cationic dithienylethenes (DTEs) and polyoxometalates (POMs) units. Single-crystal X-ray diffraction studies reveal that (1)3[PM12O40]∙5ACN (M = W, Mo) (1-PW12 and 1-PMo12) and (2)3[PM12O40]∙5ACN (M = W, Mo) (2-PW12 and 2-PMo12) are isostructural, while (2)4[Mo8O26]4DMF (2-Mo8) is an isotype of (1)4[Mo8O26]4DMF (1-Mo8) i.e., the first POM-DTE ionic assembly, recently reported. The solid-state photochromic properties of these materials at room temperature are highly tunable with the nature of the DTEs and POMs used, which has been interpreted taking into account steric and electronic factors. Especially, while 1-PMo12 and 2-PMo12 exhibit negligible photoresponses which have not been considered herein, thorough investigations of the photocoloration and fading kinetics in ambient conditions have highlighted the precise impact of both organic and inorganic components on the photoswitching abilities of 1-Mo8, 2-Mo8, 1-PW12 and 2-PW12. Upon UV-light irradiation, the absorption of the normal and mixed DTEs in their closed-ring form exhibits a hypsochromic shift which is more pronounced in hybrid systems integrating -[Mo8O26]4- rather than -[PW12O40]3-, due to the higher negative charge density of the octamolybdate unit. The photocyclization rates of DTEs are also systematically increased when combined with the -[Mo8O26]4- unit, while in contrast, their back cycloreversion rates are not affected whatever the nature of the POMs used. In addition, within isostructural series, hybrids integrating mixed DTEs exhibit faster fading processes than their normal DTE counterparts when exposed to visible light. Finally, among this new series, 2-Mo8 shows the best photochromic performances with a fast photocoloration rate associated with a high coloration contrast, a fast and complete fading process and a high cyclability

A straightforward access to photochromic diarylethene derivatives via palladium-catalysed direct heteroarylation of 1,2-dichloroperfluorocyclopentene.

International audienceA novel and efficient palladium-catalysed direct di-heteroarylation of 1,2-dichloroperfluorocyclopentene with a variety of heteroarenes is reported, giving rise to 1,2-di(heteroaryl)ylperfluorocyclopentene photochromic compounds. The reaction proceeds with thiazoles, thiophenes or furan derivatives and tolerates various substituents

Very Fast Single-Step Photoinduced Charge Separation in Zinc Porphyrin Bridged to a Gold Porphyrin by a Bisethynyl Quaterthiophene

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Intriguing Second-Order NLO Switches Based on New DTE Compounds

International audienceTwo new photochromic compounds bearing a dithienylethene unit have been designed, synthesized, and well characterized. The first contains a platinum dialkynyl moiety whereas the second bears a simple phenyl-dimethylamino fragment. Both compounds have demonstrated an excellent photochromic behavior. This efficient photochromism is the springboard for a significant photomodulation of the second-order nonlinear optical properties, determined in dichloromethane solution by means of the Electric Field Induced Second Harmonic generation technique. The results are of interest for the design of reversible NLO switches as a tool for emerging photonic technologies