The variety of reactions of radical cations derived from 2-diphenylaminothiophene oligomers

ESR spectroelectrochemical measurements of 2-diphenylamino-substituted oligothiophenes 8m proved the existence of radical cations 8 m + upon oxidation. Their stability and dimerization depend significantly on the number m of thiophene units. The radical cations 8 1 + and 8 2 + are very reactive and dimerize spontaneously to yield either 2,5-bis(diphenylamino)-2,2′-bithiophene 102 or 2,5-bis(diphenylamino)-5,5′-bis(2-thienyl)-3,3′-bithiopene 112, respectively. In contrast, the radical cations 8 3 + – 8 5 + are highly stable and do not dimerize at all.