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 flavon e, the quercetin molecule, have been investigated. The molecular confo rmation of quercetin has been obtained from semiempirical treatment wi th the AM1 Hamiltonian. Some structural modifications have been observ ed between the molecule in the solid state and in an isolated state, n otably in the rotation of the phenyl ring with respect to chromone par t of the compound. The theoretical model has been validated by both vi brational and electronic spectroscopies. The calculated vibrational an d UV-vis spectra are in good accordance with the experiments. The Rama n spectra have been assigned, and the main electronic transitions invo lved in the absorption spectrum have been characterized. (C) 1997 John Wiley & Sons, Inc.