Cobalt(II) complexes with non-steroidal anti-inflammatory drugs and α-diimines

Cobalt(II) complexes with a series of non-steroidal anti-inflammatory drugs (diflunisal, flufenamic acid, mefenamic acid and niflumic acid) in the presence of nitrogen-(2,2′-bipyridylamine, 2,2′-bipyridine, 1,10-phenanthroline) and/or oxygen-donor ligands (methanol) have been synthesized and characterized with physicochemical and spectroscopic techniques. The deprotonated NSAID ligands are coordinated to Co(II) ion through their carboxylato groups in diverse binding modes. The crystal structures of complexes [Co(diflunisal-O)2(methanol)4], [Co(niflumato-O)2(methanol)4], [Co(flufenamato-O,O′)2(2,2′-bipyridylamine)], [Co(mefenamato-O,O′)2(2,2′-bipyridylamine)] and [Co3(flufenamato-O,O′)4(flufenamato-O,O,O′)2(2,2′-bipyridine)2] have been determined by X-ray crystallography. The interaction of the complexes with serum albumins was studied by fluorescence emission spectroscopy and the albumin-binding constants were determined. The ability of the complexes to scavenge 1,1-diphenyl-picrylhydrazyl, 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and hydroxyl radicals was investigated and the complexes were more active than the corresponding free drugs. Spectroscopic (UV and fluorescence), electrochemical (cyclic voltammetry) and physicochemical (viscosity measurements) techniques were employed in order to study the binding mode of the complexes to calf-thymus (CT) DNA and to calculate the corresponding binding constants; for all complexes, intercalation was suggested as the most possible DNA-binding mode. The cobalt(II) complexes with a series of non-steroidal anti-inflammatory drugs (diflunisal, flufenamic acid, mefenamic acid and niflumic acid) and nitrogen-donor (2,2′-bipyridylamine, 2,2′-bipyridine, 1,10-phenanthroline) and/or methanol as ligands were prepared and characterized. The complexes exhibit noteworthy antioxidant activity and significant binding affinity for serum albumins and calf-thymus DNA. [Display omitted] •Nine cobalt(II) complexes with non-steroidal anti-inflammatory drugs were synthesized.•The crystal structures of five Co-NSAID complexes were determined.•The Co-NSAID complexes can bind to human or bovine serum albumins.•The complexes show significant radical scavenging activity.•Intercalation is the most possible binding mode of the complexes to calf-thymus DNA.