Electrochemical Study of 3-(N-alkylamino)thiophenes: Experimental and Theoretical Insights into a Unique Mechanism of Oxidative Polymerization

A number of conjugated polymer systems can be generated via electropolymerization, including polythiophenes and polyanilines. While both have been reported to polymerize anodically via radical coupling, the presence of the aniline nitrogen plays a significant role in the mechanism of electropolymerization. In this study, the electropolymerization mechanism of 3-(N-alkylamino)thiophenes, structural hybrids of thiophene and aniline, is studied utilizing experimental and theoretical methods. Synthesis of new short chain 3-(N-alkylamino)thiophenes is discussed, and a mechanism of electropolymerization is proposed whereby oxidation occurs through removal of a nitrogen lone pair electron, followed by a chemical step resulting in radical contribution at the 2-position of the thiophene ring. Coupling of these final radical cations thus results in a typical poly(alpha-alpha'-thiophene) backbone.