A combined substituent and supramolecular approach for improving the electron donor properties of 1,3-dithiole-2-thione derivatives

Abstract

A series of symmetrical 1,3-dithiole-2-thiones and -ones have been prepared via double lithiation of vinylene trithiocarbonate followed by trapping of the dianions with aryl carbaldehydes. The resulting diols are oxidised in high yield and the corresponding diketones are converted to thiophenes and furans using P₂S₅–NaHCO₃ and P(OEt)₃, respectively. The majority of triaryl compounds undergo two reversible oxidation processes in the range +0.86 to +1.57 V (vs. Ag/AgCl). The charge-transfer complex (8c)₂·TCNQ forms mixed donor-acceptor stacks. EPR spectroscopy confirms the presence of an open shell species, but the material is an electrical insulator. Reaction of 8c with diiodine forms a charge transfer complex with a conductivity of 1.2 × 10⁻⁴ S cm⁻¹.