Excitonic effects in thiophene oligomers

Excitonic interactions in conjugated chains are studied by analysing the optical and vibrational properties of unsubstituted thiophene oligomers with different supramolecular organization. Single quasi-planar molecules, electronically decoupled in the solid state, have been obtained by inclusion of the thiophene oligomers in perhydrotriphenylene. Resonant Raman scattering shows that the strong spectral changes which occur upon molecular aggregation can be explained only by electronic excited state interactions, in rather good agreement with the prediction of the molecular exciton model.