Chiral recognition by an asymmetrically modified clay surface was reported by one of the present authors forty years ago. However, how chiral metal complexes organize in the interlayer space of a clay mineral on a molecular scale had not been clarified. In this report, the intermolecular interactions were investigated on the clay minerals intercalating a chiral complex, D- (or L-)[Ir(bzq) 2 (phen)] + (bzqH = benzo[h]quinoline; phen = 1,10-phenanthroline). The compound had a three-bladed propeller type structure with a monovalent charge (+1). Notably, the complex formed a mono- or bi-molecular layer at the loading level of 50% and 100% CEC, respectively. The solid state vibrational circular dichroism (VCD) method was applied to detect the subtle changes of vibrational properties caused by intermolecular interactions. The work demonstrated how useful the VCD method was in revealing the details of intermolecular interactions in solid samples. The obtained results give promise to the possibility of VCD application in the fields of heterogeneous asymmetric reactions.
Applied Clay Science
Vibrational Circular Dichroism Spectroscopy toward Intercalation Compounds of Sodium Montmorillonite: Evidences for Molecular Packing of Enantiopure Monovalent Ir(III) Complexes within Interlayer Spaces