Polymerization mechanism of di(benzylidene)tetrathiapentalenes into linearly extended TTF polymers

The mechanism of the oxidative polymerization of di(benzylidene)tetrathiape ntalenes (R-DBTTP; where R = H, OCH3, CF3) into linearly extended TTF polym ers has been investigated by cyclic voltammetry at low and high scan rates. The polymerization involves as a first step the formation of the monomer r adical cations which undergo rapidly a radical dimerization reaction. The d imerization rate constants were found to be in the range of 2k(dim) = 4 x 1 0(6) to 10(7) L mol(-1) s(-1). The dimerization products slowly deprotonate to give the corresponding vinylogous tetrathiafulvalene (TTF) derivatives (k(H) = 0.02-10 s(-1)). Polymerization only occurs, if the TTF intermediate s are oxidized to the radical trication, a behavior which sharply contrasts the known electropolymerization mechanism of pyrrole or thiophene.