Ab initio HF and DFT calculations of geometric structures and vibrational spectra of electrically conducting doped oligothiophenes

Abstract

This article reports results of a theoretical study of the effect of ionization on the infrared spectra of a series of α,α′–dimethyl end-capped oligothiophenes with the purpose of obtaining a theoretical insight into the geometry and spectral changes ocurring on doping polythiophene. For that purpose we determined the structures, vibrational frequencies and infrared intensities of the neutral oligomers, their radical cations and their dications. Ab initio HF and DFT molecular orbital calculations were employed to assess the structural and spectral changes from neutral to charged states.