Chiral metal–organic frameworks constructed from four-fold helical chain SBUs for enantioselective recognition of α-hydroxy/amino acids

• Published in: Inorganic chemistry frontiers Vol. 5; no. 1; pp. 153 - 159
• Main Authors: Yao, Ru-Xin, Fu, Huan-Huan, Yu, Bo, Zhang, Xian-Ming
• Format: Journal Article
• Language: English
• Published: London Royal Society of Chemistry 2018
• Subjects: Amino acids; Chains; Crystal structure; Dichroism; Enantiomers; Inorganic chemistry; Isomers; Pharmacology; Recognition; Toxicity
• ISSN: 2052-1553; 2052-1545; 2052-1553
• DOI: 10.1039/C7QI00615B

The chiral recognition of racemic α-hydroxy/amino acids is an essential and challenging mission because enantiomers may profoundly differ in biological function, pharmacology and toxicity. Three stable, chiral 3D metal–carboxylate frameworks, namely [M 2 (bptc)(H 2 O)(MeOH)]·3H 2 O (bptc 4− = 3,3′,5,5′-biphenyltetracarboxylate, M = Co, CoNi for 1–2 , and [Ni 2 (bptc)(MeOH) 2 ]·3H 2 O for 3 ) have been successfully obtained by spontaneous resolution with an achiral ligand H 4 bptc, and they crystallize in the chiral tetragonal space group I 4 1 22, and feature chiral four-fold helical metal chains as SBUs. In particular, the Co-MOF material could be used to rapidly and sensitively recognize racemic α-hydroxy/amino acids by the intensity change of circular dichroism signals. A large relative difference of 38.59% in circular dichroism signals for d / l -mandelic acid is achieved, which may be ascribed to the specific recognition sites ( i.e. , groove of helical chains) and different bonding energies of d / l -isomers in the chiral microenvironment of the crystal structure.