Two new coordination polymers, namely poly[[hexathiocyanatotetrakis{μ3-2,4,6-trimethyl-1,3,5-tris[(triazol-1-yl)methyl]benzene}tricadmium(II)] 3.5-hydrate], {[Cd3(SCN)6(C18H21N9)4]·3.5H2O}n (1), and poly[[hexathiocyanatotetrakis{μ3-2,4,6-trimethyl-1,3,5-tris[(triazol-1-yl)methyl]benzene}trizinc(II)] 3.5-hydrate], {[Zn3(SCN)6(C18H21N9)4]·3.5H2O}n (2), have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction analysis. From the X-ray analysis, it is noteworthy that polymers 1 and 2 are isostructural, with their three-dimensional structures composed of three kinds of four-connection metal ions and two kinds of three-connection 2,4,6-trimethyl-1,3,5-tris[(triazol-1-yl)methyl]benzene (TTTMB) ligand nodes. Each metal ion is six-coordinated in a slightly distorted octahedral geometry. The antioxidant activity against DPPH (2,2-diphenyl-1-picrylhydrazyl) and the antidiabetic activity against α-amylase of the synthesized compounds were evaluated in vitro. The results of the DPPH free-radical scavenging assay showed that polymers 1 and 2 exhibited strong antioxidant effects, with IC50 values of 3.81 and 2.56 mg ml-1, respectively. The IC50 value in the antidiabetic studies of polymer 1 was 3.94 mg ml-1, while polymer 2 exhibited no antidiabetic activity. Polymers 1 and 2 revealed different inhibitory activities on DPPH and α-amylase, which indicated that the metal ions play important roles in the biological activity of coordination polymers. In addition, the solid-state photoluminescence properties and thermal stability of 1 and 2 have been investigated.
Keywords: antioxidant activity; crystal structure; fluorescence properties; three-dimensional coordination polymer; α-amylase inhibition.