Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (12): 2229-2250.doi: 10.3866/PKU.WHXB201510301

• REVIEW • Previous Articles     Next Articles

Correlation between ECD Spectra and the Absolute Configurations of Chiral Salen-Ni(Ⅱ) Complexes: a Fingerprint Role of the First ECD Band in the Visible Region

Hui. ZHANG1(),Li-Li. ZENG1,Yue-Kui. WANG2(),Shi. CAO1,Dong. GUO1,Dan. LI1,Xue-Ming. FANG1,Li-Rong. LIN1()   

  1. 1 Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian Province, P. R. China
    2 Key Laboratory of Chemical Biology and Molecular Engineering of the Ministry of Education, Institute of Molecular Science, Shanxi University, Taiyuan 030006, P. R. China
  • Received:2015-09-09 Published:2015-12-04
  • Supported by:
    the National Natural Science Foundation of China(21273175, 21273139, 21271150)

Abstract:

A correlation between the electronic circular dichroism (ECD) spectra and the absolute configurations of a serials' chiral salen-Ni(Ⅱ) complexes was investigated. The solid-state structures, absolute configurations, and preferential conformations in solution of quasi-planar chiral [Ni(salen)] complexes were studied using their crystal structures, solid-state and solution ECD spectra in combination with theoretical ECD calculations. Furthermore, two different nomenclatures for the absolute configurations of square-planar [M(salen)] complexes were inspected carefully, and suggestions for proper use of them are discussed. The calculated ECD spectra of [Ni(sal-R, R-chxn)] [sal-R, R-chxn = (R, R)-1, 2-cyclohexylene bis(salicylicdeneiminate)] in dichloromethane solution revealed that the first ECD band in the visible region was dominated by the ligandto-metal charge transfer transition (LMCT), which was incorrectly assigned to a d-d transition in the literature. When the absolute configuration of [Ni(sal-R, R-chxn)] was Λ, the first ECD absorption band in the visible region was positive. This ECD fingerprint is universally applicable for assigning the absolute configurations of other square-planar chiral [Ni(salen)] and six-coordinate trans-[Co(salen)L2] complexes with a "closed-shell" electronic structure. This work provides some insight into the coordination stereochemistry and chiroptical properties of chiral [M(salen)] complexes. Additionally, this work is significant for the understanding of chiral recognition and asymmetric catalytic mechanisms.

Key words: Salen-based Ni(Ⅱ) complex, Electronic circular dichroism, Solid-state chiroptical spectroscopy, Absolute configuration correlation, Fingerprint technique

MSC2000: 

  • O641