Copper(II) complexes containing derivative of aminobenzoic acid and nitrogen-rich ligands: Synthesis, characterization and cytotoxic potential

Abstract

Four mixed ligand copper(II) complexes bearing mefenamic acid and different heterocyclic nitrogen donor ligands have been synthesized. A direct one-step metal-ligand complexation method was adopted in synthesizing the complexes. These newly formed complexes are [Cu(mef)2(imi)2]; CM-1, [Cu(mef)2(py)2]; CM-2, [Cu2(mef)4(apy)2].2CH3CN; CM-3, and [Cu(mef)2(nic)2(C2H5OH)]; CM-4 (mef = mefenamato, imi = imidazole, py = pyridine, apy = 2-aminopyridine, and nic = nicotinamide). The complexes were characterized by both analytical and spectral methods. FTIR studies confirmed the mefenamato ligand coordinated via a deprotonated carboxylato oxygen atom to the Cu(II) center. The molecular structures of CM-1 and CM-2 showed both are isostructural and exhibit square-planar geometry around Cu(II). CM-3 crystallized in the dimeric form, each Cu(II) is in five-coordinate geometry, with a structural paddle wheel motif. The resulting square pyramidal geometry in CM-4 is due to the ethanol solvent's coordination on the pyramid's axial position. The crystal lattice of the complexes was stabilized by noncovalent interactions such as N-H···O, C-H···O, CH···π, and π···π. The mononuclear complexes were more stable than the dimeric complex CM-3, revealed by thermogravimetric analysis. In addition, the cytotoxic study of the copper (II) complexes on lung carcinoma cells (NCIH-460) and breast cells (MDAMB) were evaluated using MTT dye (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay.