Temperature dependent spectroelectrochemical measurements on end-capped oligothiophenes

Abstract

'End-capped' oligothiophenes have been synthesized as new model compounds for polythiophene. Due to the blocking of the reactive α- and β-positions of both terminal thiopene units with a cycloalkane 'cap' more precise characterization of the oligomers in various oxidation states becomes possible. Spectroelectrochemical investigations were carried out on a homologues series of 'end-capped' oligothiophenes in a thin-layer optical device providing the possibility of temperature variation during measurements. The optical absorption spectra of the electrochemically prepared oxidation states show a clear dependence on chain length and an unusual temperature dependence. The results will be discussed partially in terms of molecular polarons and bipolarons in polythiophene and in terms of π-dimerization. © 1993.