Three Novel Homochiral Helical Metal−Organic Frameworks Based on Amino Acid Ligand: Syntheses, Crystal Structures, and Properties

Three novel homochiral helical metal−organic frameworks (MOFs), namely [Zn(LTP)2] n (1), [Cd(LTP)2] n (2), and [Ni(LTP)2] n (3) (LTP = l-thioproline), have been synthesized and characterized. X-ray crystallographic analysis shows that all the three complexes consist of homochiral left-handed or right-handed helical chains. Complex 1 exhibits 1-D Zn-carboxyl right-handed helical chains constructed by pentacoordinated Zn2+ ions. Complex 2 shows a 2-D homochiral coordination framework with (4, 4) topology based on Cd-carboxyl right-handed helical chains in which Cd2+ ions are 6-fold coordinated. There are various hydrogen bonds between the adjacent helical chains in 1 and 2 which connect them into 3-D supramolecular networks. Complex 3 also exhibits a 2-D homochiral layer structure with (4, 4) topology containing Ni-carboxyl left-handed helical chains. The luminescence properties of 1 and 2 have been investigated briefly.