Electrochemical Polymerization of Pyrrole-Perimidine Hybrids: Low-Band-Gap Materials with High n-Doping Activity

Conductive π-conjugated polymers were electrochemically generated from a variety of donor-acceptor pyrroles containing fused perimidine subunits. Alternating oxidative and reductive polarization of these precursors induces multidirectional coupling involving both perimidine and acenaphtho[1,2-c]pyrrole moieties, producing cross-linked polymeric structures. Chemical oxidation experiments and computational analyses of spin densities in the charged pyrrole intermediates indicate that the formation of inter-perimidine linkages occurs prior to pyrrole-pyrrole couplings. In the resulting polymers, a very stable dication state is achievable with the positive charge located on the bis-perimidine linker. These polymers do not show any stable neutral state and can be easily reduced. Cationic and anionic states of these electrogenerated films were investigated in the solid state by UV-vis-NIR and EPR spectroelectrochemistry, assisted by DFT calculations.