Synthesis and electrochemical study of narrow band gap conducting polymers based on 2,2′-dipyrroles linked with conjugated aza-spacers

A series of 2,2′-dipyrrole monomers separated by aza-spacers (N,N′-bis-(1H-pyrrol-2-ylmethylene)-benzene-1,4-diamine; N4,N4′-bis-(1H-pyrrol-2-ylmethylene)-biphenyl-4,4′-diamine; N,N′-bis-[1-(1H-pyrrol-2-yl)-ethylidene]-hydrazine; and 4,4′-bis[(1H-pyrrol-2-yl)-diazenyl]biphenyl) have been synthesised using modified Schiff and azo-coupling reactions. The new 2,2′-dipyrroles linked with conjugated aza-spacers have been evaluated as precursors of narrow band gap conducting polymers. Electrochemically synthesized poly(N,N′-bis-[1-(1H-pyrrol-2-yl)-ethylidene]-hydrazine) displays a narrow band gap of just 0.7 eV, making it a suitable candidate for optoelectronic applications.