Synthesis and properties of higher homologs of extended TTP donors

A series of multi-fused extended tetrathiafulvalene (TTF), in which thiophene ring is inserted between two 1,3-dithiole rings in TTF (ThTTF-n, n = 3–5, 7), have been synthesized. In the electronic spectra, no significant red shift bas been observed as the number of fused extended TTFs increases. Cyclic voltammograms of the ThTTF-n are composed of n − 2 pairs of two-electron transfer waves and two pair of one-electron-transfer ones, while four pairs of single-electron-transfer waves have been observed for ThTTF-2. Molecular orbital calculation suggests the highest occupied molecular orbitals (HOMOs) of ThTTF-n spread over the molecule, while the lowest unoccupied molecular orbitals (LUMOs) are localized on the central thiophene moieties.