Cobalt(II) complexes containing mefenamic acid with imidazole and pyridine based auxiliary ligands: Synthesis, structural investigation and cytotoxic evaluation

The interaction between CoCl2.6H2O and mefenamic acid (2-[(2,3-dimethylphenyl)amino]benzoic acid) in the presence of imidazole and pyridine based ligands resulted in the formation of [Co(mef)2(imi)2]; C-1 , [Co(mef)2(nic)2(H2O)2].2H2O; C-2 , [Co2 (& mu;-H2 O)(& mu;-mef-O,O')2(mef)2(py)4].CH3CN; C-3 , and [Co2(& mu;-mef-O,O')4(apy)2].2CH3CN; C-4 , (mef is monodentate mefenamato, & mu;-H2O is bridging aqua ligand, & mu;-mef-O, O' is bridging bidentate mefenamato, imi is imidazole, nic is nicotinamide, py is pyridine, and apy is 2-aminopyridine). The complexes were characterized spectroscopically and by physicochemical properties. Single-crystal X-ray diffraction studies confirmed the structures of the complexes. In C-1 , Co(II) is in four -coordinate geometry, while in C-2 , Co(II) is in hexa-coordination with two mefenamato carboxylate oxy-gen atoms, two nitrogen atoms, and two oxygen atoms from two solvent ligands. Complex C-3 consists of two cobalt centers linked by an aqua ligand and bridged by two mefenamato ligands. Furthermore, the octahedral geometry in each Co(II) in C-3 was completed by coordinating two monodentate mefe-namato ligands and monodentate pyridine ligands. Similarly, in C-4 , a Co-Co bond connects two Co(II) centers in six-coordinate geometry, with four bidentate mefenamato ligands acting as bridges between the two Co(II) and two 2-aminopyridine nitrogen, in monodentate coordination to each Co(II). The lattice solvents in C-2 to C-4 participated in intermolecular hydrogen bonding interactions with the mefenamato ligand. FTIR studies showed the presence of both monodentate and bidentate coordination of the depro-tonated carboxylate oxygen atoms of the mefenamato ligand, as well as the coordination of the nitrogen donor ligands in the complexes. TG analysis determined the complexes' thermal stability and decomposi-tion steps and ascertained their compositions, which agreed with the analytical and X-ray crystallography studies. Furthermore, the cytotoxicity of mefenamic acid and the cobalt (II) complexes on lung carcinoma cells (NCIH-460) and breast cells (MDAMB) were assessed using MTT assay. The complexes showed higher cytotoxicity than mefenamic acid against the MDAMB cell line.& COPY; 2023 Elsevier B.V. All rights reserved.