Syntheses, redox properties, self-assembled structures, and charge-transfer complexes of imidazole-and benzimidazole-annelated tetrathiafulvalene derivatives

Article abstract of DOI:10.1246/bcsj.20130043

New tetrathiafulvalene (TTF)-type electron-donor molecules annelated with imidazole or benzimidazole moiety were designed and synthesized by the phosphite-mediated coupling reactions of imidazole- or benzimidazole-annelated 1,3-dithiole-2-thiones. The effect of imidazole-annelation on the redox properties was evaluated by theoretical calculation and electrochemical measurement, and the imidazole-annelation slightly enhances the electron-donating abilities of parent TTF and benzo-TTF skeletons. The substitution of the imidazole ring with an electron-withdrawing cyano group caused a large high potential shift of the oxidation potentials in the cyclic voltammetry and an intense intramolecular chargetransfer absorption band in the electronic spectrum. The self-assembling ability was investigated by crystal structure analysis, where solvent or counter anion mediated one-dimensional hydrogen-bonded arrays of imidazole rings were linked through φ-stacks and SγS interactions to construct multidimensional networks. The donor molecules afforded weak charge-transfer complexes with tetracyanoquinodimethane (TCNQ) and fully ionic complexes with 2,3-dichloro- 5,6-dicyanobenzoquinone (DDQ) and 2,3,5,6-tetrafluoro-TCNQ. In the crystal structures of TCNQ complex and iodine salt of a benzimidazole-annelated derivative, φ-stacking motifs, donoracceptor alternating stack, and φ-stacking dimer, respectively, were interacted through hydrogen-bonds.