Solid–solid synthesis, characterization, thermal decomposition and antibacterial activities of zinc(II) and nickel(II) complexes of glycine–vanillin Schiff base ligand

Abstract

The zinc(II) and nickel(II) complexes of glycine–vanillin Schiff base were synthesized by one-step solid–solid reaction at room temperature. The composition and structure of the complexes were characterized by elemental analyses, Fourier transform infrared spectra (FTIR), X-ray powder diffraction (XRD), and thermogravimetry and differential scanning calorimetry (TG–DSC). The crystal structure of the complexes belongs to monoclinic system with the lattice parameters: a = 0.6807 nm, b = 1.3818 nm, c = 1.2011 nm, β = 95.80° for [Zn(C10H9O4N)(H2O)3], and a = 0.7457 nm, b = 1.3331 nm, c = 1.2560 nm, β = 91.89° for [Ni(C10H9O4N)(H2O)3]·1.5H2O. The experimental results indicate that the zinc and nickel ions are all six-coordinated by imino nitrogen, carboxylic oxygen, and phenolic oxygen from the Schiff base ligand, and oxygen from three coordinated water molecules, respectively. The possible pyrolysis reactions in the thermal decomposition processes of the complexes and the experimental and calculated percentage mass loss are also given. The two complexes have the most intense antibacterial activities against Escherichia coli.