INSIGHTS INTO THE POLYMERIZATION KINETICS OF SOME ALPHA-SILYLATED THIOPHENE OLIGOMERS

Oxidation of several silylthiophene oligomers has been studied in dich loromethane and acetonitrile by cyclic voltammetry. Detailed mechanist ic studies show that the oxidative coupling of silyloligothiophenes in volves the carbon-carbon bond formation between two cation-radicals, a s previously observed for other non-silylated oligothiophenes. The lif etimes of the cation-radicals are found to be dependent on the solvent , indicating a nucleophilic assistance to the C-Si cleavage. This beha vior is in agreement with a reversible coupling step leading to the fo rmation of a dimeric cation followed by the irreversible cleavage of t he C-Si bond. Evidence for the existence of an equilibrium between the monomeric cation-radical and an associated form (pi-dimerization) has been obtained from the variation of the redox potential with the temp erature and concentration for the most stable cation-radical. (C) 1997 Elsevier Science S.A.