A new silole containing low band gap electroactive polymer

A new silole containing monomer, 1,1-dihexyl-3,4-diphenyl-2,5-bis{2-(3,4-et hylenedioxy)thienyl}silole, was synthesized by Pd-catalyzed Stills coupling reaction of the necessary 2,5-dibromosilole and 2-stannylethylenedioxythio phene derivatives. This monomer can be easily electropolymerized (E-ox,E-m = +0.29 V vs. Fc/Fc*) and yields an electroactive polymer with a low half-w ave oxidation potential (E-1/2 = -0.38 V vs. Fc/Fc*). Spectroelectrochemist ty has shown that the polymer switches between sky blue and yellow green up on doping. The low-lying LUMO levels of the siloles combined with the elect ron-rich character of the 3,4-ethylenedioxythiophene units confer upon this new polymer a low band gap of 1.4 eV (onset of the pi-pi* transition).