Synthesis and Antibacterial Activities of Transition Metal(Ⅱ) Complexes of 5-(Chloromethyl)Salicylaldehyde-Phenylalanine

A novel Schiff base, 5-(chloromethyl)salicylaldehyde-phenylalanine, and its transition metal (Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺) complexes were synthesized in ethanol. The ligand and complexes were characterized by elemental analysis, molar conductance measurement, IR, UV and TG-DTA, and their antibacterial activities were detected by paper-disc method and the double-dilution-method. The results showed that the Schiff base was the electrolyte of 1∶1 type with the formula of KHL·H₂O（L=C₁₇H₁₄O₃NCl^2-）and these five complexes were the nonelectrolytes with the formula of ［ML(H₂O)］·nH₂O. The nitrogen atom of imino group and the oxygen atoms of phenol group and carboxyl group in the ligand and one water molecule were coordinated with the central metal. The fluorescence experiments showed that the fluorescence intensity of each complex was higher than that of the Schiff base, and the zinc complex had the highest fluorescence intensity. The in vitro antibacterial experiments exhibited that all of the Schiff base and the complexes had antibacterial activities and each complexe had a higher antibacterial activity than that of the Schiff base. The copper complex had the highest antibacterial activity against Escherichia coli and Staphylococcus aureus and its minimal inhibitory concentrations (MIC) against these two bacteria were 25.0 and 12.5 μg·mL^-1 respectively.