Synthesis, characterization, crystal structure determination and antibacterial activities investigation of a series of new Ni(II), Cu(II) and Zn(II) Schiff base complexes

In this research, through the condensation reaction of 3,5-dichlorosalicylaldehyde with 1,2-ethanediamine (en), 1,3-propanediamine (pn) and 1,4-butanediamine (bn), a serious of new N2O2 salophen type Schiff base ligands (csen = 6,6'-((1E,1'E)-(ethane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(2,4-dichlorophenol), cspn = 6,6'-((1E,1'E)-(propane-1,3-diylbis(azanylylidene))bis(methanylylidene))bis(2,4-dichlorophenol) and csbn = 6,6'-((1E,1'E)-(butane-1,4-diylbis(azanylylidene))bis(methanylylidene))bis(2,4-dichlorophenol)) were synthesized and characterized using FT-IR, 1H NMR, 13C NMR, mass spectroscopy and elemental analysis. Also, their Ni(II), Cu(II) and Zn(II) complexes were synthesized and after characterization by elemental analysis and FT-IR spectroscopy, the structure of Zn(cspn) was determined by X-ray crystallography. The Schiff base ligand coordinated to the zinc ion through the phenolic oxygens, the azomethine nitrogens and the oxygens of two water molecules. Thus, the geometry around the central zinc ion was distorted octahedral. The in vitro antibacterial activities of the ligands and their complexes were evaluated against Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. The results showed that ligands and their complexes exhibited significant antibacterial activities, and also the gram-positive bacteria are more active than gram-negative bacteria.