Preparation and Structures of Dication Salts of Phenyl-Substituted TTF Vinylogues

Some TTF vinylogues 1 containing phenyl groups at the vinyl positions were synthesized. The redox properties were investigated by cyclic voltammograms, showing that they are strong electron donors and the Coulomb repulsion is decreased in the dication states. Some of the donors afforded their dication salts as single crystals by electrochemical oxidation or the reaction with CuCl2. X-ray structure analysis has revealed that the dication molecules have structures with planar TTF vinylogue units and twisted phenyl groups. The crystal structures are unusual to avoid the steric interactions of the phenyl groups.