Electroreductive polymerisation of 3-substituted 2,5-dihalothiophenes: direct electrosynthesis vs. stepwise procedure involving thienylzinc intermediates

Abstract

This work deals with the preparation of 3-substituted polythiophenes from the corresponding 3-substituted 2,5-dihalothiophenes, either in one electrochemical step or in two steps involving electrogenerated thienylzinc intermediates. The mild conditions used all along these electrochemical procedures allow the preparation of polythiophenes functionalised by a variety of groups in the 3 position. Poly(3-hexylthiophene) prepared in two steps shows a high proportion of regioregular HT-HT linkages (HT = head-to-tail). Most polymers exhibit p-doping processes in cyclic voltammetry. n-Doping processes are also observed for polythiophenes substituted either by alkyl groups or by electron-withdrawing groups.