Synthesis, Structures and Antimicrobial Activities of Novel Schiff Base Ligand and Its Metal Complexes

A novel ligand (E)-7-hydroxy-4-methyl-8-(1-(naphthalen-1-ylimino) ethyl)-2H-chromen-2-one [HOMNIEC] was synthesized by condensation of 8-acetyl-7-hydroxy-4-methyl-2H-chromen-2-one and Naphthalen-1-amine by the reported method. The metal complexes with this ligand were synthesized by using a common new method. FTIR, 1H NMR, Mass Spectrometry and TGA techniques were used to confirm their structures. The FTIR spectral data indicate that the ligand was coordinated with the metal ions through the phenolic oxygen on coumarin moiety and nitrogen of azomethine. The ligand and complexes were examined for in vitro antimicrobial activities using broth microdilution method in DMSO medium against Escherichia coli (MTCC 443) and Pseudomonas aeruginosa (MTCC 1688) a Gram-negative bacterial strain, Staphylococcus aureus (MTCC 96) and Streptococcus pyogenes (MTCC 442) a Gram-positive bacterial strain, and Candida albicans (MTCC 227), Aspergillus clavatus (MTCC 1323) and Aspergillus niger (MTCC 280) fungal strains. The metal complexes were found to have enhanced antimicrobial activities compare to the Schiff base [HOMNIEC] ligand. Especially, the antifungal activity of Cu(II) and Zn(II) ions complexes was found to be twofold more than the standard drug griseofulvin against C. albicans.