Electrochemical and spectroelectrochemical investigations of small-bandgap π-conjugated polymers and their precursors

The film-formation behaviour of 1,3-dihydro-bis-[1,3-(2-thienylmethylidene)]-isothianaphthene (2) (as a model compound for oligomerization of arenemethylidenes) under anodic oxidation has been investigated by cyclic voltammetry under a variety of reaction conditions. Detailed cyclovoltammetric and spectroelectrochemical studies of the oxidation processes of 5,5'-bis-(di-phenylmethylidene)-2,2',5,5'-tetrahydro-2,2'-bithiophene (3), 5,5'-bis-(phenyl-p-tolylmethylidene)-2,2',5,5'-tetrahydro-2,2'-bithiophene (4), 5,5'-bis-(phenyl-2-thienyl-methylidene) -2,2',5,5'-tetrahydro-2,2'-bi-thiophene (5) and 5,5'-bis-(di-2-thienylmethylidene)-2,2', phene (6) reveal two reversible oxidation steps and no oligomerization as observed for 2, Electrochemical and spectroelectrochemical investigations of electropolymerized cyanosubstituted p-conjugated polymers 7b and 8b with a small bandgap derived from beta,beta'-di-(2-thienyl)-beta,beta'-( 2,5-thiophene)-diacrylnitrile (7a) and substituted dithienylethylene 8a are reported. The electronic influence of two cyano groups and steric hindrance avoid the film formation of 1,2-dicyano-1,2-di-2-(thienyl) ethylene (9a). (C) 1998 Elsevier Science S.A.