b-Nitrostyrene derivatives—a conformational study by combined Raman spectroscopy and ab initio MO calculations

A complete conformational analysis of b-nitrostyrene and b-methyl-b-nitrostyrene derivatives was carried out by Raman spectroscopy coupled to ab initio MO calculations. Apart from the optimised geometrical parameters of the most stable conformers of the molecules under study, the corresponding harmonic vibrational frequencies were calculated, as well as potential-energy profiles for several internal rotations within the molecules. At the light of these results, a complete assignment of the Raman spectra of the solid samples was performed. The conformational behaviour of this kind of systems was found to be mainly determined by the stabilising effect of p-electron delocalisation. q 2004 Elsevier B.V. All rights reserved