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