Spectroelectrochemistry of electrogenerated tetrathiafulvalene-derivatized poly(thiophenes):: Toward a rational design of organic conductors with mixed conduction

Thin films of tetrathiafulvalene (TTF) derivatized polythiophenes were prepared by electropolymerization of precursors based on bithiophene or hybrid thiophene-ethylenedioxythiophene (EDOT). The cyclic voltammogram of these polymers exhibits an additional anodic wave between the two oxidation steps corresponding to the formation of the TTF cation radical and dication. The electrochemically induced spectral changes associated with these various oxidation processes were analyzed on equilibrated films and in dynamic conditions using classical and time-resolved spectroelectrochemical techniques. In spite of a complex behavior due to the overlap of the various TTF oxidations with the doping process of the pi-conjugated supporting PT backbone, the different monomeric and dimeric oxidized TTF species present in the polymers were unequivocally identified. Comparison of the two polymers shows that whereas for poly(1) oxidation of TTF precedes the PT doping, the presence of EDOT in the PT backbone of poly(2) leads to the reverse situation. On the basis of these results, the structural conditions required to develop a novel class of organic conductors with mixed conduction are discussed.