2-Arylazo-1-vinylpyrroles: oligomerization in the presence of protic and aprotic acids

Abstract

2-Arylazo-1-vinylpyrroles react with protic (CF3COOH, HCl) and aprotic (BF3) acids forming deeply colored oligomeric products consisting of soluble (in benzene, chloroform) and insoluble fractions with yields amounting to 73 %. According to the data from 1H NMR and IR spectroscopy oligomerization takes place mainly at the 1-vinyl group with partial involvement of the pyrrole ring. The process is accompanied by capture of the catalyzing acids by the azo group, leading to strong polarization of the elementary unit with transfer of positive charge to the pyrrole ring, which thus becomes capable of further transformations with cross-linking of oligomeric chains. The obtained oligomers possess electric conductivity of 10−13-10−9 S/cm, which is increased to 4.8∙10−6 S/cm when the products are iodinated with iodine vapor.