Synthesis, characterization, crystal structure, superoxide dismutase and biological activities of nickel (II) complexes with bidentate ligands possessing N and O donor atoms

Nickel Complexes Bearing ONS Chelating Ligands: A Promising Contender for In Vitro Cytotoxicity Effects on Human Pancreatic Cancer MIA-PaCa-2 Cells

The highly chronic human pancreatic cancer cell is one of the major reasons for cancerous death. Nickel complexes are recently gaining interest in anticancer activities on different types of cancer cells. Hence, in this study, we synthesized and characterized a series of ONS donor ligands [2-HO-C₆H₄-CH═N-(C₆H₄)-SH] (L1), [2-OH-3-OMe-C₆H₃-CH═N-(C₆H₄)-SH] (L2), [2-OH-3,5-(C(Me)₃)₂-C₆H₂-CH═N-(C₆H₄)-SH] (L3), [2-OH-C₆H₄-CH═N-(C₆H₄)-SMe] (L4), [2-OH-3-OMe-C₆H₃-CH═N-(C₆H₄)-SMe] (L5), [2-OH-3,5-(C(Me)₃)₂-C₆H₂-CH═N-(C₆H₄)-SMe] (L6) and their Ni(II) metal complexes [(MeOH)Ni(L1-L1-4H)] (1), [(MeOH)Ni(L2-L2-4H)] (2), [(MeOH)Ni(L3-L3-4H)] (3), [(L4-H)₂Ni] (4), [(L5-H)₂Ni] (5), and [(L6-H)₂Ni] (6). The single-crystal X-ray diffraction data of complexes 1 and 4 were collected to elucidate the geometry around the metal center. The anticancer activity of complexes 1-6 was investigated on human pancreatic cancer cell line MIA-PaCa-2, which revealed that complexes 4 and 6 were the most significantly effective in decreasing the cell viability of cancer cells at the lowest dose. The structure parameters obtained from single-crystal X-ray diffraction data are found to be in good agreement with the data from density functional theory and Hirshfeld surface analysis for complex 1.