THE MOLECULAR ARRANGEMENT OF CHIRAL METAL COMPLEXES ON THE SURFACE AND INTERLAYER SPACE OF SMECTITE

Abstract

The intercalation of tris-chelate metal complexes into clay minerals, in particular smectite, has attracted broad attention in terms of photochemistry, catalysis, and chiral recognition. It is of interest that they exhibit different adsorption behavior between racemic and enantiopure states on natural smectite. Their adsorption structure in the interlayer space has been, however, the topic of debate. In this short review article, my approach to clarify the adsorption structure of chiral metal complexes is described. The XRD method in a transmission mode was applied for the hybrid samples of montmorillonite and racemic tris-chelate nickel complexes, which were confined in a capillary tube. When the amount of adsorbed Ni complexes exceeds the cationic exchange capacity of montmorillonite, the obtained hybrid samples exhibit anisotropic diffraction in the 2D XRD images. The newly observed peaks were attributed to the reflections from the (10), (11), and (21) planes of the hexagonal assembly of Ni complexes. Based on the results, the detailed arrangement of racemic Ni complexes in the clay interlayer space is also discussed.