Condensed five-membered heterocycles with potentialities as conducting polymers: ab initio electronic structures and theoretical valence X-ray photoelectron spectra

Abstract

The electronic structures of pyrrolo-[2,3-b]- and -[3,2-b]-pyrroles, and the equivalent thienopyrroles and thienothiophenes have been investigated by MNDO and STO-3G ab initio calculations on model molecules. In agreement with previously reported u.v. photoelectron spectral data and semiempirical calculations, the [3,2-b] derivatives display lower ionization potentials than their [2,3-b] homologues. For two compounds, a discrepancy regarding the nature of the HOMO is found between these theoretical results and ours. As experimental X-ray photoelectron spectral data have to be obtained, simulated valence X-ray spectra based on the molecular intensity model proposed by Gelius have been calculated.