Comparative Study of Homochiral and Racemic Chiral Metal-Organic Frameworks Built from Camphoric Acid

Abstract

The study of the crystallization of homochiral or racemic chiral framework materials from enantiopure or racemic ligands is an important step for the rational design of crystalline homochiral materials. The self-assembly of extended frameworks in the presence of enantiopure or racemic ligands is regulated by the differing symmetry requirements of the ligand. By employing both enantiopure and racemic ligands as cross-linking ligands, we have prepared three homochiral and three racemic chiral compounds and their synthesis and structural and topological properties are presented here. It is shown that depending on the chemical compositions and framework topologies, the effect of the ligand handedness on the resulting crystal structure can vary greatly. The ligand handedness can have negligible effect on the crystallization, which leads to an interesting example of two pairs of isostructural achiral and homochiral structures with two types of six-connected nets. In another example reported here, the racemic chiral−chiral conversion is accompanied by the twofold supercell formation with homochiral layers and racemic chiral layers pillared in two unique patterns.