Some divalent metal(II) complexes of salicylaldehyde-derived Schiff bases: Synthesis, spectroscopic characterization, antimicrobial and in vitro anticancer studies

Mononuclear transition metal(II) complexes of the type M(L)(2.) 2H(2)O (where M = Co, Ni, Cu, Zn) have been synthesized from uninegative Schiff base ligands (HL1-HL4) designed by condensation of 4-fluorobenzylamine with 2-hydroxy-1-naphthaldehyde/3,5-dichlorosalicylaldehyde/3,5-dibromosalicylaldehyde/3-bromo-5-chlorosalicylaldehyde. The compounds were successfully characterized using spectroscopic and physiochemical methods together with elemental analysis. Spectroscopic elucidation indicates a monobasic bidentate nature of ligands coordinated via deprotonated phenolic oxygen and azomethine nitrogen atom which suggests an octahedral geometry around the central metal ions. The complexes and ligands were screened for their in vitro antimicrobial activity against bacterial and fungal strains, the zinc(II) complexes being more active against the tested microbial strains. Further, the metal complexes were found to be more active than the uncomplexed ligands due to chelation process and, moreover, the complexes were more active against fungal strains than bacterial strains. Cytotoxic activities of all compounds were evaluated towards human alveolar adenocarcinoma epithelial cell line (A549), human breast adenocarcinoma cell line (MCF7), human prostate cancer cell line (DU145) and one normal human lung cell line (MRC-5) using MTT colorimetric assay with doxorubicin as a standard. The zinc complexes were most active against the cancer cell lines and also found to be less toxic against MRC-5 normal cell line than standard doxorubicin.