Radical cations and anions from some simple polythiophenes: An ESR investigation

The radical cations and anions of the four lower oligomers of thiophene have been generated and characterized by means of ESR spectroscopy, with the exception of bi- and quinque-thienyl radical cations. cis-trans isomerism about the interannular bonds, similar to that previously reported for 2,2?-dithienyl radical anion, has been observed for terthienyl cation and anion radicals, while no direct evidence of such isomerism could be obtained for quaterthienyl and quinquethienyl.