Abstract
Tetrathiafulvalene (TTF) can be self-associated in face-to-face mode under neutral and cation radical states. We report here the study of self-association behavior of cation radicals derived from benzenes connected with ethynyltetrathiafulvalenes. The electrochemical oxidation of 2 and 3 revealed that these compounds show three-step oxidation wave as a result of forming mixed valence dimers. The electronic spectra of the cation radicals also showed the association properties. Partly oxidized cation radicals have charge-resonance absorptions at around 2000nm owing to associates. The electronic spectra of cation radicals, 23+ and 34+, showed large Davydov blue shift of the absorptions at 700-800nm. This blue shift indicates the stacking of cation radical. Moreover, the conductivities of these cation radicals, which were prepared by iodine doping method, reflected the face-to-face stack mode.
