Molecular structure and vibrational spectroscopic studies of Chrysin using HF and Density Functional Theory

In the present study, the molecular confirmation, vibrational and electronic transition analysis of 5,7-dihyroxyflavone (Chrysin) were investigated using experimental techniques (FT-IR, FT-Raman and UV) and quantum chemical calculations by HF and DFT/B3LYP method with 6-31G(d,p) as basis set. The FT-IR and FT-Raman spectra in solid phase were recorded in the region 4000-400cm(-1) and 3500-50cm(-1) respectively. The UV absorption spectra of the title compound dissolved in water, methanol and ethanol were recorded in the range of 200-400nm. The complete vibrational assignments were performed on the basis of total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanic (SQM) method. By using TD-DFT calculation, electronic absorption spectra of the title compound have been predicted and a good agreement with experimental one is established. In addition, the molecular electrostatic potential (MEP), natural bond orbital (NBO) analysis have been investigated using theoretical calculations. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule.