Title: Square planar Ni(II), Pd(II), and Pt(II) complexes with new Schiff base ligand (E)-N-cyclohexyl-2-(2-hydroxy-5-methoxy-3-nitrobenzylidene)hydrazine-1-carbothioamide and solvent DMSO: Synthesis, Characterization, X-ray diffraction and anticancer activity

Abstract

The ligand H2L (E)-N-cyclohexyl-2-(2-hydroxy-5-methoxy-3-nitrobenzylidene) hydrazine-1-carbothioamide has been synthesized by the reaction between 2-hydroxy-5-methoxy-3-nitrobenzaldehyde and N-cyclohexylhydrazinecarbothioamide. This ligand was coordinated to metal ion Pd(II) and Pt(II) in basic medium in a mixture of DMSO and methanol solvent. The square planar complexes [PdL.dmso] and [PtL.dmso] were formed via N-S-O coordinating sites of ligand and the fourth coordination bond was formed via S of DMSO which was used as a solvent. The square planar Na [NiL.OAc] complex was formed methanol solvent, whereas CH3COO- occupied the fourth coordinating site. The FTIR, UV-Vis, and 1H and 13C NMR spectroscopy methods were used to characterize the synthesized compounds. The CHN elemental analysis was carried out to determine molecular formula. The two complexes structure of palladium [PdL.dmso] and platinum [PtL.dmso] were completely elucidated with single crystal X-ray diffraction analysis. The cytotoxicity of the synthesized compounds L, a, b and c were tested against cancer cell lines, Hela and human normal endothelial cell lines (Eahy926) by MTT assay. The palladium complex [PdL.dmso] showed the highest activity among all the compounds with IC50 = 15.6 µM against Hela. The nickel and platinum complexes a and c showed significant activity against Hela with IC50 = 105.7 µM and IC50 = 166 µM respectively. The ligand showed very poor activity against Hela cell lines. The nickel complex showed the highest cytotoxicity with IC50 = 5.8 µM and the complexes a, b and ligand, L exhibited the activity with IC50 = 43.3 µM, IC50 = 45 µM, and IC50 = 185 µM respectively against Eahy926. The palladium complex b showed potential activity with a very good selectivity index (SI=2.8) against Hela cell lines. The coordinated complexes showed higher activity than free ligand due to metalation increased lipophilicity. The group 10 metal complexes could be the promising cancer therapeutic agents.