Vibrational Spectroscopic Study of a Series of α,α‘-Diethyl End-Capped Oligothiophenes with Different Chain Lengths in the Neutral State

In this paper, we investigate the vibrational FT-IR and FT-Raman spectra of a series of α,α‘-diethyl substituted oligothiophenes with variable chain lengths (from trimer to hexamer) in the neutral state. The experimental data support the existence of an effective intramolecular delocalization of the π electrons. Ab initio quadratic force field calculations, at the RHF/6-31G** level, have been carried out for each oligomer, with the chain length dependence of the Raman spectra being simulated with remarkable accuracy.