Manifestation of Supramolecular Chirality during Adsorption on CsCuCl3 and γ-Glycine Crystals

Abstract

The chirality of biopolymers and its emergence from the racemic prebiotic world is one of the key mysteries of science. There are many versions on how the total chiral balance breaking occurred, but they all face an insoluble challenge—the impossibility of a total shift of the chiral balance towards the formation of biopolymers based only on D-sugars and L-amino acids. A possible solution to this problem lies in the asymmetric autocatalysis on chiral crystals. Since the reaction is heterogeneous, it is important to study the features of adsorption on the surface of crystals. In this paper, the adsorption of limonene, α-pinene, and menthol enantiomers on γ-glycine and CsCuCl3 crystals was studied. Single-crystal X-ray crystallography, SEM, and porosimetry were used as auxiliary methods. The t-test was used to determine the reliability of chiral recognition. It was shown that both crystals were capable of chiral recognition at high coverages. The mechanism of supramolecular chiral recognition was identical to that of the chiral crystals studied previously. However, neither γ-glycine nor CsCuCl3 showed chiral recognition with respect to all enantiomers. In fact, γ-glycine crystals showed recognition for limonene enantiomers, and very high recognition in the case of menthol enantiomers. CsCuCl3 crystals showed the capability to recognize enantiomers of α-pinenes only. This led to the conclusion that the recognition of enantiomers by a supramolecular chiral surface is not universal.