Vibrational circular dichroism and single crystal X-Ray diffraction analyses of [Ir(bzq)2(phen)]+ (bzq = benzo[h]quinoline; phen = 1,10-phenanthroline): absolute configuration and role of CH–π interaction in molecular packing

Abstract

Vibrational circular dichroism (VCD) spectra are measured for dichloromethane solutions of the resolved enantiomers of [Ir(bzq)₂(phen)]⁺ (bzqH = benzo[h]quinoline; phen = 1,10-phenanthroline). The absolute configuration of each enantiomer is determined by comparing the experimental and theoretical spectra. The result is in accord with the results of the X-ray single crystallographic analysis on the enantiomeric crystal. Moreover, the importance of the CH–π interaction is derived between phen and a hydrogen atom in bzq in the molecular packing of both the enantiomeric and racemic crystals. A helical column is formed in the enantiomeric crystal in the tetragonal space group P4₃, whereas a tight racemic pair is formed in the racemic crystal in the monoclinic space group P2₁/n.