Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (07): 1633-1639.doi: 10.3866/PKU.WHXB20110707

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

Theoretical Analysis of the ECD Spectra of SalenCo(III) Complexes Containing Axial Imidazole Ligands

SU Xiao-Ling1, WANG Yue-Kui1, WANG Yan2, JIA Jie1, GAO Xiao-Li1   

  1. 1. Key Laboratory of Chemical Biology and Molecular Engineering of the Ministry of Education , Institute of Molecular Science, Shanxi University, Taiyuan 030006, P. R. China;
    2. Department of Chemistry and Chemical Engineering, Lüliang University, Lüliang 033000, Shanxi Province, P. R. China
  • Received:2011-02-01 Revised:2011-05-01 Published:2011-06-28
  • Contact: WANG Yue-Kui E-mail:ykwang@sxu.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (20673069) and Natural Science Foundation of Shanxi Province, China (2007011021).

Abstract:

The geometries of the cobalt complexes [Co(MeO-salen)(Im)2]+, [Co(MeO-salen)(2-MeIm)2]+,and [Co(MeO-salen)(MeIm)2]+ (Im=imidazole; MeIm=1-methylimidazole, 2-MeIm=2-methylimidazole, MeO- salenH2=salen type Schiff base: (R,R)-N,N′-bis(5-methoxy-salicylidene)-1,2-diiminocyclohexane) in dichloromethane solution were optimized using density functional theory (DFT) at the B3LYP level of theory with the mixed basis set: 6-31G* for C and H, and 6-311+G(2d,p) for Co, N, and O atoms. Based on the optimized geometries the excitation energies, oscillator and rotational strengths, and the electronic circular dichroism (ECD) spectra of the complexes were calculated using time-dependent density functional theory (TDDFT) with the same functional and basis sets. In these calculations solvent effects were included using the polarized continuum model (PCM). The calculated ECD spectra are in good agreement with the observed ones. Detailed analyses of the dominant transitions reveal that the first circular dichroism (CD) band in the long wavelength region is dominated by the ligand-to-metal charge transfer transition π→d, which was wrongly assigned to a d→d transition in the literature. The introduction of imidazole ligands to the axial positions has no influence on the sign of the first two CD bands, but it does have a significant influence on the shape and intensity of the CD spectra. For complexes with the λ(RR) chiral configuration the first CD absorption band is positive and the second is negative. These findings provide a deep insight into the electronic structures and chiroptical properties of the chelates.

Key words: Schiff-base complexes of cobalt(III), Axial imidazole ligand, Circular dichroism spectrum, TDDFT calculation, Chiroptical property

MSC2000: 

  • O641