Antoine Vacher

Radical or not radical: compared structures of metal (M = Ni, Au) bis-dithiolene complexes with a thiazole backbone.

A complete series of dianionic, monoanionic, and neutral dithiolene complexes formulated as [Ni(Et-thiazdt)2](n), with n = -2, -1, 0, and Et-thiazdt: N-ethyl-1,3-thiazoline-2-thione-4,5-dithiolate, is prepared using an optimized procedure described earlier for the N-Me derivatives. Electrochemical and spectroscopic properties confirm the electron-rich character of the Et-thiazdt dithiolate ligand. The three complexes are structurally characterized by single-crystal X-ray diffraction. The paramagnetic anionic complex [Ni(Et-thiazdt)2](-1), as Ph4P(+) salt, exhibits side-by-side lateral interactions leading to a Heisenberg spin chain behavior. The solid-state structure of the neutral, diamagnetic [Ni(Et-thiazdt)2](0) complex shows a face-to-face organization with a large longitudinal shift, at variance with the structure of its radical and neutral gold dithiolene analogue described earlier and formulated as [Au(Et-thiazdt)2](•). Comparison of the two structures, and those of the other few structurally characterized pairs of Ni/Au dithiolene complexes, demonstrates the important role played by overlap interactions between gold dithiolene radical species. Despite its closed-shell character, the neutral nickel complex [Ni(Et-thiazdt)2](0) exhibits a semiconducting behavior with a room-temperature conductivity σRT ≈ 0.014 S cm(-1).

The near infra red (NIR) chiroptical properties of nickel dithiolene complexes

Enantiomerically pure dianionic, monoanionic and neutral dithiolene complexes formulated as [Ni((R,R)-CHMePh-thiazdt)2]−2,−1,0 and [Ni((S,S)-CHMePh-thiazdt)2]−2,−1,0 (CHMePh-thiazdt: N-(1-phenylethyl)-1,3-thiazoline-2-thione-4,5-dithiolate) have been synthesized from the enantiopure N-(1-phenylethyl)-1,3-thiazoline-2-thione precursors. The electrochemical and spectro-electrochemical investigations carried out on these complexes show that the CHMePh-thiazdt ligands act as electron rich ligands and that the complexes are strong near infrared (NIR) absorbers in the range of 800–1100 nm for the neutral species and 1050–1500 nm for the reduced radical anion species. Circular dichroism (CD) thin layer spectro-electrochemical experiments carried out on the neutral (R,R) enantiomer, [Ni((R,R)-CHMePh-thiazdt)2], revealed a redox switching of CD-active bands, not only in the UV-vis but also in the NIR region.

A sulfur-rich π-electron acceptor derived from 5,5′-bithiazolidinylidene: charge-transfer complex vs. charge-transfer salt

Novel π-electron acceptors are still highly desirable for the formation of conducting salts or as n-dopable semiconductors. We describe here two synthetic approaches to substitute a dicyanovinylidene group, CC(CN)2 to a thioketone (CS) in the recently described DEBTTT acceptor where DEBTTT stands for (E)-3,3′-diethyl-5,5′-bithiazolidinylidene-2,4,2′,4′-tetrathione. These electron withdrawing groups enhance the electron accepting ability as demonstrated through electrochemical investigations, without hindering the formation of short intra- and intermolecular S⋯S contacts in the solid state. Association of this acceptor 1 with tetramethyltetrathiafulvalene (TMTTF) and decamethylferrocene (Fe(Cp*)2) afforded 1 : 1 adducts which were analyzed by single crystal X-ray diffraction. Combined with vibrational and magnetic properties, it appears that [TMTTF][1] behaves as a neutral charge-transfer complex while [Fe(Cp*)2][1] is an ionic salt. The concentration of the spin density on the exocyclic sulfur atoms in 1−˙ favors the setting of direct antiferromagnetic interactions in [Fe(Cp*)2][1].

Interplay between Organic–Organometallic Electrophores within Bis(cyclopentadienyl)Molybdenum Dithiolene Tetrathiafulvalene Complexes

Tetrathiafulvalenes (TTF) and bis(cyclopentadienyl) molybdenum dithiolene complexes, Cp2Mo(dithiolene) complexes, are known separately to act as good electron donor molecules. For an investigation of the interaction between both electrophores, two types of complexes were synthesized and characterized. The first type has one Cp2Mo fragment coordinated to one TTF dithiolate ligand, and the second type has one TTF bis(dithiolate) bridging two Cp2Mo fragments. Comparisons of the electrochemical properties of these complexes with those of models of each separate electrophore provide evidence for their mutual influence. All of these complexes act as very good electron donors with a first oxidation potential 430 mV lower than the tetrakis(methylthio)TTF. DFT calculations suggest that the HOMO of the neutral complex and the SOMO of the cation are delocalized across the whole TTF dithiolate ligand. The X-ray crystal structure analyses of the neutral and the mono-oxidized Cp2Mo(dithiolene)(bismethylthio)TTF complexes are consistent with the delocalized assignment of the highest occupied frontier molecular orbitals. UV-vis-NIR spectroelectrochemical investigations confirm this electronic delocalization within the TTF dithiolate ligand.

Ionic Self-Assembly and Red-Phosphorescence Properties of a Charged Platinum(II) 8-Quinolinol Complex Associated with Ammonium-Based Amphiphiles

A series of ionic associates based on the platinum(II) chelate of 5-sulfo-8-quinolinol, [Pt(qS)2](2-), and ammonium-based amphiphiles is described. At variance with the prototypical neutral complex Pt(q)2 (q=8-quinolinol), these dianionic fluorophores, functionalized at the periphery with sulfonate groups, can be associated by the ionic self-assembly approach with various ammonium cations, such as (H2n+1Cn)2Me2N(+) (n=12, 16, 18) or complex ammonium cations carrying three Cn carbon chains (n=12, 14, 16) and an additional amide group. Investigations of their luminescence properties in solution, in the solid state, and, when possible, in thin films revealed that the phosphorescence properties in condensed phases are directly correlated to intermolecular interactions between the luminescent [Pt(qS)2](2-) centers. Of particular interest is also the formation of a columnar liquid-crystalline phase around room temperature (between -25 and +180 °C), as well as the very good film-forming ability of some of these fluorophores from organic solvents.

Enhancing light trapping of macroporous silicon by alkaline etching: application for the fabrication of black Si nanospike arrays

The synthesis of highly absorbing silicon (black Si (BSi)) is a very active research topic with promising applications in the field of sustainable energies, ultrasensitive sensing and antibacterial materials. Here, we show that extended alkaline etching of macroporous Si, fabricated by photoelectrochemical etching, drastically influences the surface structures as well as their optical properties. We demonstrate that this treatment can considerably improve the light trapping of the surface and we finally show that it is possible to use it for fabricating very quickly highly-absorbing arrays of sharp and crystalline BSi nanospikes (NSpikes).

Chiral 1,2-dithiine as a sulfur rich electron acceptor

The selective synthesis of both enantiomers of a sulfur rich electron acceptor containing two 1-phenylethyl groups of the same chirality and a chiral axis is described. Cyclisation into enantiopure dithiine has been induced by the presence of a chiral substituent on the nitrogen atom of a thiazoline-2-thione dithiolate precursor.