Conjugation-Extended Tetrathiafulvalene Analogues Involving a Central Aromatic 5-Membered Heterocyclic Linking Group

Abstract

Conjugation-extended tetrathiafulvalene analogues, 2,5-bis(1,4-dithiafulven-6-yl)thiophene (2a), 2,5-bis[2,3-bis(methoxycarbonyl)-1,4-dithiafulven-6-yl]thiophene, and 2,5-bis(1,4-dithiafulven-6-yl)furan, involving an aromatic heterocyclic linking group have been synthesized by the Wittig condensation reaction of 2,5-thiophene- and 2,5-furandicarbaldehydes with 1,3-dithiol-2-ylidenetributylphosphorane and its 4,5-bis(methoxycarbonyl) derivative. The electrochemical redox properties of these compounds in solution have been investigated by cyclic voltammetry in order to evaluate the effect of the linking group on the donating ability and the thermodynamic stability of the radical cations. Whereas the radical cations are not so stable, complexes of 2a with 2,3-dichloro-5,6-dicyano-p-benzoquinone and iodine were found to show relatively high conductivities ((1.0—1.1) × 10⁻³ S cm⁻¹) on a compressed pellet at room temperature.