Solvent-controlled assembly of helical coordination polymers based on lactate synthon from two-dimensional layer to three-dimensional framework

Abstract

Compound (R)-4-(1-carboxyethoxy)-2-methylbenzoic acid ((R)-H2cma) was prepared from (S)-methyl lactate and 4-hydroxy-2-methylbenzoic acid. (R)-H2cma as chiral synthon assembled with 1,3-di(pyridin-4-yl)propane (1,3-dpp) and Ni2+ ions to obtain helical chiral complexes {[Ni2((R)-cma)2(1.3-dpp)2]·H2O}n (HU18-R) and {[Ni2((R)-cma)2(1.3-dpp)2(H2O)]·3H2O}n (HU19-R) in different solvent systems. Single crystal tests revealed that HU18-R is a two-dimensional (2D) structure with two independent Ni2+ centers and HU19-R is a three-dimensional (3D) framework containing dinuclear [Ni2(CO2)2(H2O)]2+ clusters. Four types of helices were formed in HU18-R and HU19-R by chiral transfer or induction. In HU18-R, small right-handed (R)-cma-Ni chain and large right-handed (R)-cma-Ni-1.3-dpp chain were constructed by chiral transfer. For HU19-R, helical nano-channel based on achiral 1.3-dpp ligands and Ni2+ ions was obtained from chiral induction method and small (R)-cma-Ni chain was built from chiral transfer. As semi-conducting materials, HU18-R and HU19-R indicate strong absorption capacity for UV–vis light and low-impedance properties. Under UV light, they have noticeable catalytic effects for degradation of methylene blue (MB). Moreover, magnetic tests confirmed that HU18-R and HU19-R have ferromagnetic and antiferromagnetic properties, respectively.