Synthesis, characterization and investigation of cytotoxic and antioxidant properties of mixed-ligand thiosemicarbazone complexes

In this work, 31 mixed-ligand metal complexes of nickel(II), copper(II), zinc(II), and cobalt(II) with salicylaldehyde-derived N-methyl-, N-phenyl-, and S-methyl- thiosemicarbazone compounds substituted with different groups were synthesized. In these complexes, diethanolamine, pyridine, 4-methylpyridine, 3,5-dimethylpyridine, 2,6-dimethylpyridine, 2,4,6-trimethylpyridine, 2,6-dimethylaniline, and 2,2'-bipyridine as secondary ligands were used. The structural characterization of the synthesized compounds was performed by using elemental analysis and spectroscopic methods (IR, UV-Vis, ESI-MS, 1H-NMR), and the structures of 16 complexes were confirmed by single crystal X-ray diffraction analysis. The antioxidant activities of the ligands and complexes were investigated using DPPH and CUPRAC methods, and their cytotoxicities were evaluated against K562, THP-1, MDA-MB-231, HCT116, and HUVEC cell lines using the MTT assay. The results were assessed to examine the structure-activity relationship based on the effects of substituents on the salicylaldehyde, the methyl and phenyl groups on the thiosemicarbazone, the metal ion, and the secondary ligand.