Syntheses, Crystal Structures, and Properties of Binuclear Copper(II) Complexes Derived from 2-Aminopyridines

3-Methyl-2-aminopyridine (L-1) and 5-bromo-2-aminopyridine (L-2) were used as ligands respectively, and two novel binuclear copper(II) complexes, [Cu-2(CH3COO)(4)(L-1)(2)] (1) and [Cu-2(CH3COO)(4)(L-2)(2)] (2), have been synthesized by the reaction of the above-mentioned ligands with anhydrous cupric acetate in ethanol solution. The two copper(II) complexes were characterized by the methods of melting point, FT-IR, UV-Vis, fluorescence spectra, and HRMS. The crystal structures of 1 and 2 were analyzed by single-crystal X-ray diffraction, which indicates that 1 crystallizes in the orthorhombic system with Pbca space group, while 2 crystallizes in the monoclinic system with P2(1)/n space group. Each of the two binuclear Cu(II) complexes contains two copper center cations, four acetate ions, and two L-1 or L-2 ligands. Each acetate acts as a bridging ligand and coordinates to two Cu(II) cations forming a cage. like structure. Each Cu(II) cation in complexes 1 or 2 is pentacoordinate to one N atom in one pyridine ring and four O atoms in four acetate ions, and the geometries around Cu(II) in 1 or 2 are distorted square pyramid. The antibacterial activities of 1 and 2 were investigated by the agar diffusion method, and the result indicated that 1 and 2 had good antibacterial inhibiting effects against Staphylococcus aureus, Bacillus subtilis, and Escherichia coli. And their antioxidant activities were valued using the 2,2-diphenyl-1-picrylhydrazyl (DPPH center dot) method, which showed that both of them possessed good scavenging capability on DPPH center dot. Moreover, the electrochemical properties of 1 and 2 were studied by the cyclic voltammetry method, and the results indicate that 1 and 2 showed quasi-reversible redox processes. CCDC: 2123588, 1; 2123589, 2.

Automated summary

Two novel binuclear copper(II) complexes were synthesized and characterized, and their antibacterial, antioxidant, and electrochemical properties were investigated.