Vibrational Circular Dichroism (VCD) for Intercalation Compounds of Sodium Montmorillonite

Evidence for Molecular Packing of Monovalent Iridium (III) Complexes within Interlayer Spaces of Sodium Montmorillonite

Molecular packing in intercalation states was reflected on the relative intensity of a VCD signal.

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.

Published: 26 Jul 2022


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Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Number JP17H03044, JP19K05508, JP20K21090
JSPS Fellows (JP21J15602)