[Quantum chemistry study on fluorescence spectra of four flavonoid compounds]

The semi-empirical method PHF/PM3 of quantum chemistry was used for studying the fluorescence spectra of four flavonoid compounds. Firstly, the geometries of these four compounds were optimized by energy gradient method. The results show that in these four copmounds, the two six-membered rings on the left are in the same plane, but these are different torsion angles between this plane and the benzene-ring plane on the right. Secondly, vibrational analyses were performed for the four optimized configurations. There is no imaginary frequency in vibrational analyses. This indicates that the optimized configurations are essentially reasonable. Finally, on this basis, the electronic spectra were calculated by CIS method. All the calculated results are basically consistent with experimental values.