Syntheses, structure and properties of vinylogous EDO-TTFs

We synthesized vinylogous 4,5-ethylenedioxy-tetrathiafulvalenes (EDO-TTFs), 4,5-ethylenedioxy-2,2′-ethanediylidenebis(1,3-dithiole) (EDO-EBDT), 4,5-dimethyl-4′,5′-ethylenedioxy-2,2′-ethanediylidenebis(1,3-dithiole) (DMEDO-EBDT), 4,5-bis(thiomethyl)-4′,5′-ethylenedioxy-2,2′-ethanediylidenebis(1,3-dithiole) (BTMEDO-EBDT), and 4,5-bis(methoxycarbonyl)-4′,5′-ethylenedioxy-2,2′-ethanediylidenebis(1,3-dithiole) (BMCEDO-EBDT). The cyclic voltammograms of the vinylogous EDO-TTFs show two pairs of single-electron redox waves. The first oxidation potentials ( E 1) of vinylogous EDO-TTFs are lower than those of the related TTFs, indicating that the electron donating abilities of new donors are stronger than those of the corresponding TTFs. The smaller E 2− E 1 values of new donors compared with those of the related TTFs suggest a decrease in the on-site Coulombic repulsion in the dication state. X-ray crystal structure analysis of BMCEDO-EBDT reveals that the inter-molecular C-H⋯O type hydrogen bond is constructed between the hydrogen atom and the oxygen atom of the ethylenedioxy group. Single crystalline TCNQ complexes of DMEDO-EBDT and BTMEDO-EBDT have been prepared and their conducting properties and crystal structure have been investigated. The TCNQ complexes of DMEDO-EBDT and BTMEDO-EBDT show low electrical conductivities ( σ rt