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We have studied the Fourier transform Infrared (FT-IR) and the Fourier transform Raman (FT-Raman) spectra of a well– barrier– well thiophene-based oligomer oxidized with dry iodine vapour. These new data, when combined with the full vibrational assignment of the oligomer in the neutral state, provide a complete spectroscopic characterization of a new positive polaron-type model defect in an electronic segmented molecule. The FT-IR and FT-Raman spectra were also calculated at the B3LYP/6– 31G^** level as an aid to the vibrational assignment of the main bands in the whole spectral range. Copyright © 2000 John Wiley & Sons, Ltd.

Raman spectroscopy and the self-consistent reaction field (SCRF) theory were used to study structural and vibrational features of the amino acid L-asparagine in H2O and D2O solutions. Ab initio methodology at the RHF/6–31+G* level were used to evaluate the minimum energy structure, quadratic force field, vibrational wavenumbers and infrared intensities of this molecule in a polar medium. Raman spectra from aqueous solutions of asparagine and its ND3⁺ and ND2 deuterated isotopomers were recorded and a general assignment of the measured bands was proposed on the basis of the isotopic shifts. The results were successfully supported by a scaled 6–31+G*/SCRF quantum-mechanical force field. © 1997 John Wiley & Sons, Ltd.

The vibrational Fourier transform infrared and Fourier transform Raman spectra of two neutral thiophene-based oligomers in solution and in the solid state were studied. The compounds have a well–barrier–well structure, where the well parts are two biothiophene or terthiophene end moieties and the barrier part is a dimethylene fragment with a larger energy gap. Characteristic features are correlated with vibrational data on one-dimensional unsubstituted α-oligothiophenes and α,α'-dimethyl end-capped oligothiophenes. Vibrational assignments are also proposed for relevant bands in the whole spectral range. © 1997 John Wiley & Sons, Ltd.