Infrared and Raman features of a series of α,ω-bis(arylthio)oligothiophenes as molecular wires. A π-electron delocalization efficiency study

Fourier transform infrared and Raman spectra of a novel series of neutral α,ω-bis(mesitylthio)oligothiophenes and some α,ω-bis(mesitylthio)oligothiophenes containing ethylenedioxy groups at the β positions, with various chain lengths have been investigated. Because these compounds contain carbon-sulfur linkages they can be viewed as models for prototypical surface-bound molecular wires in which the oligomer is linked to the surface by a thiol-metal bond. Thus, interactions between the conjugated moiety and the metallic surface or cluster can be simulated. These studies are very important in order to apply molecular systems in micro and optoelectronic devices. The statements of effective conjugation coordinate theory and density functional theory calculations let us describe the specific electronic interactions between the mesitylthio groups and the oligothiophene backbone. An increased π-electron delocalization or conjugation length with respect to the α,ω-bis(alkyl)oligothiophenes of the same length has been noticed. The inclusion of C–S bridges between the end groups and the central π-conjugated backbone increases the π-electron delocalization within the oligomeric chain and precludes the oligothiophene moiety from conjugative interactions with the mesityl rings.