Spectroelectrochemical Raman study of two end-capped sexithiophenes with applications as electroactive molecular materials

In this paper, the vibrational Fourier transform Raman spectra of two sexithiophenes with the end alpha-positions substituted with n-hexyl or n-thiohexyl groups are studied. We investigate the effects of the different side chains on the intramolecular pi-electron delocalization in neutral state and the charged defects generated upon p-doping. Density functional theory and ab initio quantum-chemical calculations are performed on various oligothiophene model compounds as an aid in the interpretation of the experimental data. The analysis of the peculiar Raman features of these pi-conjugated systems has been guided by formalism of the effective conjugation coordinate theory. The Raman study of this class of materials is a powerful tool to derive information about the delocalization of pi-electrons in the pristine state and the charged species upon doping.