Organic solvent–luteolin interactions studied by FT-Raman, Vis-Raman, UV-Raman spectroscopy and DFT calculations

Abstract

The interactions of luteolin with three alcohols (methanol, 1-propanol, 1-butanol) and dimethylsulfoxide (DMSO) were studied by FT-Raman, Vis-Raman and UV-Raman spectroscopies, coupled to density functional theory calculations. No large shift was observed for the bands in the spectra of luteolin in alcohols or DMSO in the 1700–1550 cm− 1 region. This is possibly related to the presence of a strong intramolecular hydrogen bond involving the 5-OH and the carbonyl of luteolin, as suggested by literature data [V. Exarchou, A. Troganis, I.P. Gerothanassis, M. Tsimidou, D. Boskou, Tetrahedron 2002, 58, 7423–7429] and DFT calculations. Furthermore, DFT calculations suggest that the CO stretching of luteolin is implicated in several vibrational modes, whereas the most upshifted band in the 1700–1550 cm− 1 can be interpreted as arising mainly from a 5-OH bending. The results are discussed in the framework of vibrational spectroscopy studies on flavonoids, of the photophysical properties of luteolin, and of the reported literature of vibrational spectra of luteolin under different conditions, in particular when interacting with biomolecules.