关键词: 醌, 取代基, 电子转移, 从头计算法

AM1, ab initio (at HF/3-21G, HF/6-31G^* levels) and DFT [at B3LYP/6- 31G^*, B3LYP/6-311G (d, p) levels] studies on the structure and electron transfer properties of p-quinone, ubi-Q~0, ubi-Q~1, ubi-Q~2 and their radical anions were performed. The results show that substituents effect on the structure and properties of quinone is significant. All the atoms of p-quinone and its anion are located on the same plane. However, the planes of ubi-Q~0, ubi-Q~1, ubi-Q~2 and their anions' rings are slightly puckered because of the substituents effect. With the changing of the structure, the charge distribution of ubi-Q~0, ubi-Q~1, ubi-Q~2 and their anions are changed. The charges are no longer spread on the molecule evenly. This results in the changing of the dipole moments. The results of ionization potentials and electron affinities show that the longer the substituent group is, the more easily an electron can be transfered. On the basis of the above results, the electron self-exchange processes of p-quinone and ubi-Q were studied. The internal reorganization energy and the solvent reorganization energy were calculated. Results of internal reorganization energy indicate that not only the high frequency vibrations but also the low frequency vibrations contribute to the internal reorganization energy considerably, and there is no direct relationship between the volume of the system and the internal reorganization energy. The calculated rate constant of benzoquinone electron self-exchange reaction in aqueous is 2.38×10^7mol^-^1.s^-^1, which is close to 6.20× 10^7mol^-^1.s^-^1, determined experimentally. The rate constants of ubi-Q~0, ubi-Q~1, and ubi-O~2 electron self-exchange reactions in aqueous are 8.02× 10^7mol^-^1.s^-^1, 3.81×10^6mol^-^1.s^-^1 and 1. 46× 10^7mol^-^1.s^-^1 respectively.

Key words: QUINONE, SUBSTITUENT GROUP, AB INITIO CALCULATION