Abstract: Tectorigenin and tectoridin were optimized by using ab initio HF and DFT B3LYP method, and the characteristics of the frontier molecular orbitals and the distribution of energy levels were analyzed. Time Depended Density Function Theory(TD-DFT) B3LYP and semi-empirical ZINDO method were employed to claculated electronic structure and spectrum properties of tectorigenin and tectoridin. It was found that the main absorption spectra originate from the π→π^* electronic transition among the molecules orbitals. The change on the molecular structure can affect the distribution of the frontier molecular orbitals of the titled compounds and change absorption spectra property, and make UV spectra red shift to withdrawing electronic group. The TD-DFT and ZINDO methods can be employed for the calculation of spectra properties of the compounds.

Key words: Tectorigenin, Tectoridin, TD-DFT, ZINDO, Absorption spectra