Synthesis, characterization and In Vitro biological studies of metal schiff bases

Abstract

Transition metal complexes of symmetrical and asymmetrical Schiff bases have played a significant role in the field of coordination, inorganic and bioinorganic chemistry as models for biological, analytical and industrial applications. The thesis deals with the synthesis, characterization and in vitro biological studies of metal Schiff bases. Three symmetrical and unsymmetrical tetradentate Schiff bases: [HLL1, ehopd], [HLL2, ehata], [HLL3, ehbta] with the N2O2 chromophore, eight unsymmetrical tridentate Schiff bases: [HLL4, ehmta] [HLL5, ehben], [HLL6, ehmez], [HLL7, ehacp], [HLL8, ehacn], [HLL9, ehvan], [HLL10, ehvet], [HLL11, ehbzc] with the N2O chromophore alongside their corresponding Ru(III), Zn(II), Cu(II), Ni(II) and Co(II) complexes were synthesized and characterized by elemental analyses, melting point/decomposition temperature FTIR and UV-Vis spectroscopy. The results of the spectroscopic studies revealed that the Schiff base ligands coordinated to metal ions through the (>C=N) nitrogen and phenolic oxygen atoms with evidence of new bands due to the ν(M-N) and ν(M-O) vibrations respectively in the spectra of metal complexes. The antibacterial activity of the metal complexes, tetradentate and tridentate Schiff bases was screened against three Gram-positive bacteria, viz. Staphylococcus aureus, Streptococcus faecalis, Bacillus cereus and three Gram-negative bacteria viz. Pseudomonas aeruginosa, Escherichia coli, and Shigella flexineri. The evaluation results revealed that the metal complexes exhibited higher antibacterial activity than the free Schiff base ligands. In addition, in vitro antioxidant activities of the compounds were also investigated through their scavenging effect on 1,1-Diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-Azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radicals. It was observed that Ru(III) and metal(II) complexes exhibited strong scavenging activities against DPPH radical and moderate activities against ABTS radical. The compounds were screened in vitro against three cancer cell lines: human renal cancer cell (TK-10), human melanoma cancer cell (UACC-62) and human breast cancer cell (MCF-7) using the SRB assay. The results demonstrated that treatment with the synthesized compounds affected cell viability efficiently toward MCF-7 cells.