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

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journal contribution
posted on 19.10.2015, 00:00 by Toshiki Higashino, Olivier Jeannin, Tadashi Kawamoto, Dominique Lorcy, Takehiko Mori, Marc Fourmigué
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.