LINEARLY EXTENDED TETRATHIAFULVALENE ANALOGS WITH DITHIENYL AND DIFURYL POLYENES PI-CONJUGATED SPACERS

The synthesis of new classes of extended hybrid tetrathiafulvalene ana logues built around difuryl and dithienyl polyenic pi-conjugated space rs containing n = 1, 2, or 3 conjugated double bonds and bearing CO(2) Me, SMe, and n-propyl substituents (R) at the 1,3-dithiole ring is des cribed. The electronic absorption spectra of these compounds show that the wavelength of the absorption maximum and the HOMO-LUMO energy gap depend on the nature of the heterocycle, the length of the pi-conjuga ted spacer and the electronic effects of R. Cyclic voltammetry shows t hat except for n = 1 and R = CO(2)Me, all compounds are directly oxidi zed into their dicationic state through a single-step two-electron tra nsfer. The combined effects of the various structural parameters allow oxidation potentials lying among the lowest reported to date for TTF analogues to be reached.