Raman spectra and conformational properties of hexyl- and methylsulphanyl-substituted oligothiophenes

A Raman study on bithiophenes β-functionalized with hexyl and methylsulphanyl (SCH3) groups and a quaterthiophene β-functionalized with methylsulphanyl groups is reported. MM2 calculations were carried out on the hexyl derivatives and the results compared to those derived from Raman data. Evidence was obtained of the fact that the conformational preferences of alkyl bithiophenes are the same both in dilute solution and as pure liquids. Raman data confirm the efficiency of the SCH3 group in compensating the loss of π conjugation.