3-Alkylthiopyrroles: synthesis and oxidative polymerization to conductive materials

Abstract

3-Alkylthiopyrroles are obtained by decarboxylation of 4-alkylthiopyrrole-2-carboxylic acids, in turn prepared by alkaline hydrolysis of the corresponding methyl ester. These compounds were accessible by thiocyanation of 2-methoxycarbonylpyrrole, followed by alkylation in basic media. Anodic coupling of 3-thioalkylpyrroles in 0.1 mol dm^–3 tetraethylammonium perchlorate (TEAP)+ acetonitrile produces polypyrrole films which are reversibly oxidized around 0.0 V vs. Ag/Ag⁺ with 0.3 electrons per monomeric unit. Polymers were characterized by IR reflectance spectroscopy and elemental analysis. Conductivities are in the range (1–30)× 10^–3 S cm^–1.