Binuclear Schiff base copper(II) complexes: Syntheses, crystal structures, HSA interaction and anti-cancer properties

Three binuclear Schiff base copper(II) complexes: [Cu-2(HL1)(2)(CH3OH)(NO3)]center dot NO3 (1), [Cu-2(HL2)(2)(CH3OH)(2)]center dot 2NO(3) (2), and [Cu-2(HL3)(2)(C2H5OH)(2)]center dot 2NO(3) (3) [HL1 = (E)-N'-(5-fluoro-2-hydroxybenzylidene)benzohydrazide, HL2 = (E)-N'-(5-chloro-2-hydroxybenzylidene)benzohydrazide, and HL3 = (E)N'-(5-bromo-2-hydroxybenzylidene)benzohydrazide], were synthesized and characterized employing various spectroscopic techniques. X-ray crystallography analysis revealed complexes 1-3 to have similar molecular structures. Results from the MTT assay revealed that all copper complexes displayed greater cytotoxicity toward several tumor cell types than cisplatin or the Schiff-base ligands. Further investigations revealed that complex 1 can induce mitochondrion-mediated apoptotic cell death. In addition, the interaction between these Cu(II) complexes and human serum albumin (HSA) was also investigated.