Structural study of quercetin by vibrational and electronic spectroscopies combined with semiempirical calculations

As a follow-up to structural studies of monohydroxylated flavones, the structural and spectroscopic properties of a tetrahydroxylated flavone, the quercetin molecule, have been investigated. The molecular conformation of quercetin has been obtained from semiempirical treatment with the AM1 Hamiltonian. Some structural modifications have been observed between the molecule in the solid state and in an isolated state, notably in the rotation of the phenyl ring with respect to chromone part of the compound. The theoretical model has been validated by both vibrational and electronic spectroscopies. The calculated vibrational and UV-vis spectra are in good accordance with the experiments. The Raman spectra have been assigned, and the main electronic transitions involved in the absorption spectrum have been characterized. © 1997 John Wiley & Sons, Inc. Biospect 3: 183–193, 1997