CONJUGATION-EXTENDED TETRATHIAFULVALENE ANALOGS INVOLVING A CENTRAL AROMATIC 5-MEMBERED HETEROCYCLIC LINKING GROUP

Conjugation-extended tetrathiafulvalene analogues, 2,5-bis(1,4-dithiaf ulven-6-yl)thiophene (2a), 2,5-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 Witti g condensation reaction of 2,5-thiophene- and 2,5-furandicarbaldehydes with 1,3-dithiol-2-ylidenetributylphosphorane and its 4,5-bis(methoxy carbonyl) derivative. The electrochemical redox properties of these co mpounds in solution have been investigated by cyclic voltammetry in or der to evaluate the effect of the linking group on the donating abilit y 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 hi gh conductivities ((1.0-1.1) x 10(-3) S cm-1) on a compressed pellet a t room temperature.