Cobalt(II) complexes with the non-steroidal anti-inflammatory drug mefenamic acid in the presence or absence of nitrogen donor heterocyclic ligands (2,2'-bipyridine, 1,10-phenanthroline or pyridine) have been synthesized and characterized with physicochemical and spectroscopic techniques. The experimental data suggest that mefenamic acid acts as deprotonated monodentate ligand coordinated to Co(II) ion through a carboxylato oxygen. The crystal structures of tetrakis(methanol)bis-(mefenamato)cobalt(II), 1 and (2,2'-bipyridine)bis(methanol)bis(mefenamato)cobalt(II), 2 have been determined by X-ray crystallography. The EPR spectra of complexes 1 and 2 in frozen solution reveal that they retain their structures. UV study of the interaction of the complexes with calf-thymus DNA (CT DNA) has shown that the complexes can bind to CT DNA and bis(methanol)bis(pyridine)bis-(mefenamato)cobalt(II) exhibits the highest binding constant. Competitive study with ethidium bromide (EB) has shown that the complexes can displace the DNA-bound EB indicating that they bind to DNA in strong competition with EB. The cyclic voltammograms of the complexes recorded in dmso solution and in the presence of CT DNA in 1 : 2 dmso : buffer (containing 150 mM NaCl and 15 mM trisodium citrate at pH 7.0) solution have shown that they can bind to CT DNA by the intercalative binding mode. Mefenamic acid and its cobalt(II) complexes exhibit good binding propensity to human or bovine serum albumin protein having relatively high binding constant values. The antioxidant activity of the compounds has been evaluated indicating their high scavenging activity against hydroxyl free radicals and superoxide radicals.

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The structural features of copper(II), nickel(II), cobalt(II) and zinc(II) complexes with the antimicrobial drugs quinolones and non-steroidal anti-inflammatory drugs (NSAIDs) as ligands are discussed. The binding properties of these complexes to biomolecules (calf-thymus DNA, bovine or human serum albumin) are presented and evaluated. The biological activity (antimicrobial, antioxidant and antiproliferative) of selected complexes is investigated. Further perspectives concerning the synthesis and the biological activity of novel complexes with quinolones or NSAIDs attractive to synthetic chemists, biochemists and/or biologists are presented.

Copper(II) complexes with the non-steroidal antiinflammatory drug mefenamic acid in the presence of aqua or nitrogen donor heterocyclic ligands (2,2'-bipyridine, 1,10-phenanthroline, 2,2'-bipyridylamine or pyridine) have been synthesized and characterized. The crystal structures of [(2,2'-bipyridine)bis(mefenamato)copper(II)], 2, [(2,2'-bipyridylamine)bis(mefenamato)copper(II)], 4, and [bis(pyridine)bis(methanol)bis(mefenamato)copper(II)], 5, have been determined by X-ray crystallography. UV study of the interaction of the complexes with calf-thymus DNA (CT DNA) has shown that the complexes can bind to CT DNA and [bis(aqua)tetrakis(mefenamato)dicopper(II)] exhibits the highest binding constant to CT DNA. The cyclic voltammograms of the complexes in the presence of CT DNA solution have shown that the complexes can bind to CT DNA by the intercalative binding mode verified also by DNA solution viscosity measurements. Competitive studies with ethidium bromide (EB) indicate that the complexes can displace the DNA-bound EB suggesting strong competition with EB. Mefenamic acid and its complexes exhibit good binding propensity to human or bovine serum albumin protein having relatively high binding constant values. All the compounds have been tested for their antioxidant and free radical scavenging activity as well as for their in vitro inhibitory activity against soybean lipoxygenase showing significant activity.

Zinc complexes with the third-generation quinolone antibacterial drugs levofloxacin and sparfloxacin have been synthesized and characterized. The deprotonated quinolones act as bidentate ligands coordinated to zinc ion through the pyridone and a carboxylato oxygen atom. The crystal structures of [bis(aqua)bis(levofloxacinato)zinc(II)], 1, and [bis(sparfloxacinato)(1,10-phenanthroline)zinc(II)], 3, have been determined by X-ray crystallography. The biological activity of the complexes has been evaluated by examining their ability to bind to calf-thymus DNA (CT DNA) by UV spectroscopy and viscosity measurements. UV studies of the interaction of the complexes with DNA have revealed that they can bind to CT DNA probably by the intercalative binding mode which has also been verified by DNA solution viscosity measurements. The DNA binding constants have been also calculated. A competitive study with ethidium bromide (EB) showed that the complexes exhibit the ability to displace the DNA-bound EB indicating that they bind to DNA in strong competition with EB for the intercalative binding site. The interaction of the complexes with human and bovine serum albumin proteins has been studied by fluorescence spectroscopy showing that the complexes exhibit good binding propensity to these proteins having relatively high binding constant values. The biological properties of the complexes have been evaluated in comparison to the previously reported Zn(II) complexes with the first- and second-generation quinolones oxolinic acid and enrofloxacin.