Solvent and Achiral Crystalline Phase-Induced Chiral Resolution of CsCuCl3

Abstract

The chiral resolution of optically active compounds is essential owing to the different interactions between enantiomers. Although several well-established methods exist for resolving chiral organic compounds, techniques for the chiral resolution of inorganic crystals remain underdeveloped. In this study, we demonstrate the chiral resolution of CsCuCl3 using organic solvents and an achiral crystalline phase. Whereas crystallization from aqueous solutions typically yields racemic twin crystals, the addition of organic solvents to the crystallization medium led to the formation of enantiopure single crystals of CsCuCl3. Among the various water-miscible organic solvents, ethylene glycol and 1-pentanol were the most effective, producing enantiomorphic crystals. The crystal morphology was found to depend on the solvent used, indicating its influence on the crystal growth process. Additionally, an achiral crystalline phase, Cs3Cu3Cl8(OH), was obtained during the crystallization. When this achiral phase was used as the seed, homochiral CsCuCl3 crystals grew on its surface, suggesting that chiral resolution can be induced by crystallization on an achiral template.