Absolute sense of twist of the benzil molecule in its enantiomorphous crystals and inclusion complexes with optically active hosts

The solid-state CD spectra were measured for optically active trigonal crystals of benzil (dibenzoyl) and its crystalline inclusion complexes with cholic and deoxycholic acids. The observed negative Cotton effect corresponding to the lowest energy n-pi* transition was correlated with the P helicity of thr strongly twisted alpha -diketone moiety. The absolute configuration of the enclathrated guest molecule in the 1:2 inclusion complex between benzil and cholic acid was also determined by X-ray crystal analysis. (C) 2001 Elsevier Science Ltd. All rights reserved.