In order to reassign recently reported resonance Raman spectra of the reduced forms of 1,4-benzoquinone (BQ), ab initio MO and density functional calculations have been carried out for evaluating fundamental vibrational frequencies of BQ, BQ-, BQ2- and their various isotopomers. Comparing with the reported experimental frequencies and their isotope shifts of BQ, the vibrational frequencies calculated by using Becke's 1988 exchange functional with Perdew-Wang's 91 gradient-corrected correlation functional (BPW91) are closest to the corresponding experimental data. Due to the reliability of the BPW91 results, the vibrational frequencies of BQ, BQ-, BQ2- and their various isotopomers calculated with this unified method have been employed to further discuss the assignments of the recently reported resonance Raman (RR) bands of the BQ- and BQ2-. The previous assignments of the most vibrational bands are well confirmed. However, based on the calculated results, it is more reasonable to reassign the three bands at 1046, 748 and 638 cm-1 in the spectra of the BQ- existing in CH3CN to the fourth b2u, the b1g and the fourth b3g fundamental modes, respectively. It seems also reasonable to assign the weaker band at 864 cm-1 appeared in the spectra of BQ2- in the aqueous solution to the first b2g fundamental mode, though we cannot completely exclude the possibility of the first au fundamental mode before the RR spectra of the 16O2/18O2-substituted BQ2- isotopomer in the region below 800 cm-1 are obtained.
|Number of pages||12|
|State||Published - Apr 15 1998|
Bibliographical noteFunding Information:
This project was partially supported by Grant-in-Aids for Scientific Research (No.09304057) of Ministry of Education, Science, Sports and Culture of Japan, and by the Foundation of the State Education Commission of China. C.G.Z wishes to thank Dr. Zhao for a detailed discussion of the experimental results, and to thank Japan Society for Promotion of Science (JSPS) for providing financial support to his visit in Institute for Molecular Science as a JSPS fellow.
ASJC Scopus subject areas
- Physics and Astronomy (all)
- Physical and Theoretical Chemistry