Raman, infrared and computational analysis of genistein and its methoxy derivatives

Structural vibrational analyses of four 5-hydroxyisoflavones: genistein, biochanin A, prunetin and 4′,7-dimethoxygenistein have been performed using a combination of computational and experimental investigations of Raman and infrared spectra. Normal vibrational modes in the Raman and infrared spectra were assigned and correlated with the aid of calculations using density functional theory (DFT), adopting the B3LYP functional with the 6-31+G(d) basis set. As the four isoflavones differ by methoxy substitutions of the hydroxyl groups, shifts between phenol and anisole were also used to assist in the assignments. This work offers insight into some of the variations observed in the vibrational spectra of genistein and other isoflavones and lays the foundation for analysis of related compounds as well as further spectral analysis of the present isoflavones.

► Vibrational spectra of four 5-hydroxyisoflavones are studied. ► Spectra are correlated with the aid of theory and related spectra. ► Pre-requisite insight for understanding SERS of isoflavones.