DFT study of structural, vibrational and electronic properties of polyaniline pernigraniline model compounds

•Deep insight of both chemical & physical properties of two model compounds of PANI.•Detailed spectral analysis towards understanding of compound’s chemical properties.•Better understanding of structural parameters of PANI–PNB chain.•HOMO–LUMO analysis – understanding possible tuning for desired electronic properties.

Polypernigraniline is the only polyaniline to possess a doubly degenerate ground state. In the present work using density functional theory (DFT) calculations, the structural, vibrational and electronic properties of two well-known model compounds of polyaniline pernigraniline have been investigated. A detailed vibrational analysis of phenyl-end-capped dimer (B2Q1) and phenyl-end-capped tetramer (B3Q2) have been presented and complete assignments are reported. Lower region spectral assignments which were not being reported earlier are being done in the present work. DFT calculations with 6-31G** basis set produces very good results of IR and Raman spectra allowing better understanding of these compounds. TD–DFT calculations for HOMO–LUMO analysis give insights into the electronic structure of these model compounds.