Dominique Lorcy

A Single-Component Molecular Metal Based on a Thiazole Dithiolate Gold Complex

A single component molecular conductor has been isolated from electrocrystallization of the monoanionic gold bis(dithiolene) complex based on the N-ethyl-1,3-thiazoline-2-thione-4,5-dithiolate (Et-thiazdt) ligand. The crystal structure of the system exhibits layers built from parallel uniform one-dimensional stacks of the planar molecule. At room temperature and ambient pressure the system is semiconducting (0.33 S x cm(-1)) with a small activation energy. However, the single crystal conductivity is strongly pressure dependent reaching 1000 S x cm(-1) at 21 kbar. At 13 kbar there is a crossover between semiconducting and metallic regimes. Thus, the present system is the first well characterized single-component molecular metal without TTF dithiolate ligands. First-principles DFT calculations show that the ground state is antiferromagnetic with a very small band gap. A simulation of the effect of pressure on the electronic structure provides a rationale for the observed variations of the conductivity and gives insight on how to further stabilize the metallic state of the system.

Acetylacetone substituted tetrathiafulvalenes: towards new redox active ligands

Abstract A simple synthesis of novel ligands containing tetrathiafulvalenes (TTF) is reported. These compounds have been prepared by introducing an acetylacetone coordination function on the preformed donor core.

Pyridyldithiafulvenes as precursors of coordination-driven self-assembled redox active macrocycle.

A novel redox active macrocycle including two vinylogous tetrathiafulvalenes (TTFVs) and two molybdenum tetracarbonyl fragments has been synthezised thanks to the coordination-driven self-assembly of complementary angular derivatives. Pyridyl vinylogous TTFVs have been deliberately elaborated for that purpose, using the oxidative coupling of pyridyldithiafulvenes (DTF). Cyclic voltammetry, IR and NMR spectroscopies, and single-crystal X-ray crystallography of the target molecules have been investigated.

Air-stable n-channel organic field-effect transistors based on a sulfur rich π-electron acceptor

Thin-film and single-crystal n-channel organic field-effect transistors are built from the sulfur rich π-electron acceptor, (E)-3,3′-diethyl-5,5′-bithiazolidinylidene-2,4,2′,4′-tetrathione (DEBTTT). Different source and drain electrode materials are investigated: gold, the conducting charge transfer salt (tetrathiafulvalene)(tetracyanoquinodimethane), and carbon paste. Regardless of the nature of the electrodes, air-stable n-channel transistors have been obtained. Single crystals exhibit a higher performance than the thin-film transistors with a mobility of up to 0.22 cm2 V−1 s−1. These thin-film and single-crystal devices exhibit excellent long-term stability as demonstrated by the mobility measured during several weeks. The high mobility and air stability are ascribed to the characteristic three-dimensional S–S network coming from the thioketone sulfur atoms.

Anodic behaviour of mono- and bisdithiafulvenyl-9,9′-spirobifluorene: insertion of vinylogous TTF into the spirobifluorenyle framework

Abstract New three-dimensional copolymers containing 9,9′-spirobifluorenyl-ethylene units were prepared by anodic oxidation of 9,9′-spirobifluorenes 2-mono- or 2,7′-disubstituted by a dithiafulvenyl unit. The synthesis, physicochemical properties and electrochemistry of both monomers and derived oligomers and polymers are reported.

Electrosynthesis and redox behavior of vinylogous TTF displaying strong conformational changes associated with electron transfers

Abstract The redox properties of a series of substituted vinylogous tertrathiafulvalenes (TTF) prepared by oxidative coupling of 1,4-dithiafulvenes (DTF) have been investigated in acetonitrile and dichloromethane. The different steps of the electrodimerization mechanism have been characterized: fast electron transfer, coupling between two cation-radicals and slow deprotonation. Through the substituent choice of DTF, it is possible to control the relative stabilities of the different redox species of the electrogenerated vinylogous TTF. According to the nature and position of the substituent, the structural changes induced by the steric interactions lead to a compression of potential (where the second electron is easier to remove than the first one), or on the contrary to a large increase of the separation between the first and second oxidation potentials (by comparison with similar molecules without steric hindrance). Density functional modeling calculations and detailed analysis of the electrochemical behavior have been used to rationalize the substituent effect. A good agreement with the occurrence of an EE mechanism in which the electron transfer is concerted with the conformation changes is found. The inner reorganization energies are low (0.35–0.45 eV) allowing a fast passage between the different conformations during the electron transfers.

Unsymmetrical and highly-conjugated tetrathiafulvalene and selenatrithiafulvalene derivatives: synthesis and reactions of novel heterocyclic Wittig–Horner reagents

Novel 1,3-dithiole and 1-selena-3-thiole Wittig–Homer reagents have been developed and used in the efficient synthesis of a range of new, unsymmetrical tetrathiafulvalene and selenatrithiafulvalene derivatives (6)–(10) and (16); cyclic voltammetry establishes that these molecules are efficient π-donors.

A Single-Component Conductor Based on a Radical Gold Dithiolene Complex with Alkyl-Substituted Thiophene-2,3-dithiolate Ligand

Alkyl-substituted thiophene-2,3-dithiolate ligands are prepared through a Thio-Claisen rearrangement of 4,5-bis(propargylthio)-1,3-dithiole-2-thione derivatives. The two novel dithiolate ligands, namely, 4,5-dimethyl-thiophene-2,3-dithiolate (α-Me2tpdt) and 4-ethyl-5-methyl-thiophene-2,3-dithiolate (α-EtMetpdt), are engaged in anionic Au(III) square planar complexes formulated as [Au(α-Me2tpdt)2](-) and [Au(α-EtMetpdt)2](-), isolated as Ph4P(+) salts. Monoelectronic oxidation gives the neutral radical complexes [Au(α-Me2tpdt)2](•) and [Au(α-EtMetpdt)2](•). The latter crystallizes into uniform stacks with limited interstack interactions, giving rise to a calculated half-filled band structure. It exhibits a semiconducting behavior with room temperature conductivity of 3 × 10(-3) S cm(-1), indicating that this single-component conductor can be described as a Mott insulator. The different structures observed in [Au(α-EtMetpdt)2](•) and the known [Au(Et-thiazdt)2](•) complex (Et-thiazdt: N-ethyl-thiazoline-2-thione-4,5-dithiolate), despite their very similar shapes, are tentatively attributed to differences in the electronic structures of the ligand skeleton.

Self-organization of a tetrasubstituted tetrathiafulvalene (TTF) in a silica based hybrid organic–inorganic material

A hybrid organic inorganic nanostructured material containing a TTF core substituted by four arms exhibited a high level of both condensation at silicon (96%) and self-organization as evidenced by X-ray diffraction and an unprecedented birefringent behaviour.

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).