Cu(II), Ni(II) and Co(II) complexes with homoscorpionate Bis(2-Mercaptobenzimidazolyl) and Bis(2-Mercaptobenzothiazolyl)borate ligands: Synthesis and in vitro cytotoxicity studies

The salt metathesis reaction of sodium precursors, Na[H2B(mb)2] (Hmb = 2-mercapto-benzimidazole) and Na[H2B(mbt)2] (Hmbt = 2-mercapto-benzothiazole) of bipodal scorpionate ligands with Cu(OAc)2, CoCl2 and NiBr2 afforded six metal complexes, 1–6. The metal complexes were characterized using a combination of HR ESI-MS spectrometry, elemental analysis and IR spectroscopy. The cytotoxicity effect of these complexes was assessed on three human cancerous cell lines: MCF-7 (breast carcinoma), A549 (lung carcinoma) and SW1116 (colon adenocarcinoma) and compared with that for cis-platin. Our results indicated that all complexes had desirable antitumor activities (<100 µM). Copper complexes, 1 and 4, exhibited the highest anti-proliferative activity on all investigated cell lines, which are more effective than Ni and Co containing complexes and even cis-platin. The complex 1 also showed genotoxic effect and could effectively induce apoptosis in tumor cells. Molecular docking simulation studies on the synthesized complexes confirmed that 1 had the highest DNA-binding energy as their proposed targets, as well.