Copper(II) complexes with benzhydrazone-related ligands: synthesis, structural studies and cytotoxicity assay

The dinuclear copper(II) complexes [Cu-2(L-H)(2)] (1), [Cu-2(L-3OMe)(2)] (2), [Cu-2(L-4OMe)(2)] (3) as well as the tetranuclear complex [Cu-4(L-3OMe)(4)] center dot 4MeOH center dot 2H(2)O (2a center dot 4MeOH center dot 2H2O), (where L-H = 2-oxybenzaldehyde benzhydrazonato, L-3OMe = 3-methoxy-2-oxybenzaldehyde benzhydrazonato or L-4OMe = 4-methoxy-2-oxybenzaldehyde benzhydrazonato) were synthesized by reacting copper(II) acetate with the corresponding aroylhydrazone. Reactions in the presence of N-donor ligands D (pyridine, 4,4'-bipyridine or 1,10-phenanthroline) afforded complexes with different nuclearities and Cu: L : D ratios. They can be classified as dinuclear, [Cu2(L-H)(2)(py)(2)] (1py), [Cu-2(L-3OMe)(2)(py)(2)] center dot 3H(2)O (2py center dot 3H(2)O), [Cu-2(L-4OMe)(2)(py)(2)] (3py), [{Cu(L-H)}(2)(bpy)] (1bpy), [{Cu(L-3OMe)}(2)(bpy)] (2bpy), and [{Cu(L-4OMe)}(2)(bpy)] (3bpy), mononuclear [Cu(LH)(phen)] (1phen), [Cu(L-3OMe)(phen)] (2phen) and [Cu(L-4OMe)(phen)] (3phen), and polynuclear [{Cu(LH)} 2(bpy)] n center dot 2nMeOH (1bpy* center dot 2MeOH) complexes. Conversion of complexes 1py-3py to complexes 1-3 proceeded via solid state reactions. The crystal and molecular structures of 2a center dot 4MeOH center dot 2H(2)O, 2py center dot 3H(2)O, 3py, 1bpy* center dot 2MeOH, 2bpy, 1phen and 3phen were determined by the single crystal X-ray diffraction method. All complexes were characterized by means of elemental and thermogravimetric analysis, FT-IR spectroscopy and the powder X-ray diffraction method. In vitro cytotoxicity of benzhydrazone-related ligands and their copper(II) complexes against THP-1 and HepG2 cells demonstrated that the complexes are significantly more cytotoxic than the corresponding ligands.