Abstract: The configurations of the title compounds were optimized at the B3LYP/6-31G level. The results show that there is no imaginary frequency in the vibrational analysis. The ¹³C NMR spectra of the compounds were studied at the same level by the GIAO method. The calculated results show that there exist intramolecular hydrogen bonds in the three flavonol derivatives, and the bond lengths are estimated to be about 0.17~0.18 nm. The effects of hydroxyl substituents on the chemical shifts of the adjacent carbons are also discussed. It appears that the more donated electrons from the substituent groups to benzene, the larger the chemical shifts of the adjacent carbons will change.

Key words: flavonol derivatives, nuclear magnetic resonance, chemical shift