Raman study of α-oligothiophenes and model compounds of poly(thienylene vinylene)

In this work, we present a complete vibrational study of a series of the α-coupled oligothiophenes. Both experimental and theoretical investigations have been carried out by using spectroscopic techniques such as Raman Scattering and infrared absorption and analysed as a function of the oligomer length. Detailed calculations lead to a clear assignment of the vibrational modes in all compounds and to determination of a main force constants associated with the different chemical bonds. In a similar way, Raman studies of model compounds of poly(thienylene vinylene) (PTV), such as 1–2 bis (thienylene) vinylene (2TV) and 2–5 bis (2-thienyl vinyl) thiophene (3T2V) have been carried out. The two modes associated with the CC stretching of the vinyl group and the thiophene ring respectively are found to slightly depend on the length of the compounds.