Determination of the Structures of Chiral Molecules Using Vibrational Circular Dichroism Spectroscopy

摘要

Chiral molecules exhibit Vibrational Circular Dichroism (VCD) [1]. The VCD spectrum of a chiral molecule is dependent on its structure. It is extremely sensitive to the Absolute Configuration: enantiomeric molecules exhibit mirror-image VCD spectra. In the case of flexible molecules, it is also dependent on the conformation. Thus, in principle, VCD spectroscopy permits both the determination of the Absolute Configuration and the Conformational Analysis of chiral molecules. To date, VCD has not been widely used. Until recently, it has not been practicable to reliably extract structural information from VCD spectra. Recently, this situation has been radically altered by the development of a methodology permitting the prediction of VCD spectra with very high reliability [2]. This methodology is based on Density Functional Theory (DFT) [3] and uses Gauge-Invariant Atomic Orbitals (GIAOs) [4]. We refer to it here as the DFT/GIAO methodology. The accuracy of this methodology, when state-of-the-art density functionals and suitable basis sets are used, is remarkable [5]. It permits, for the first time, the routine application of VCD spectroscopy to structural chemistry.