Manganese(II) complexes with the non-steroidal anti-inflammatory drug tolfenamic acid (Htolf) with the nitrogen-donor heterocyclic ligands 1,10-phenanthroline (phen), pyridine (py), or 2,2'-bipyridylamine (bipyam) and/or the oxygen-donor ligands H2O or N,N-dimethylformamide (DMF) have been synthesized and characterized. The crystal structures of complexes [Mn(tolf-O)(tolf-O,O')(phen)(H2O)], [Mn2(μ2-tolf-O,O')2(tolf-O,O')2(bipyam)2], [Mn2(μ2-H2O)(μ2-tolf-O,O')2(tolf-O)2(py)4]·1.5MeOH·py, and [Mn(μ2-tolf-O,O')2(DMF)2]n have been determined by X-ray crystallography. The interaction of the complexes with serum albumin proteins was investigated, and relative high binding constant values were calculated. The ability of the compounds to scavenge 1,1-diphenyl-picrylhydrazyl, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid), and hydroxyl radicals was evaluated, and [Mn(tolf)2(phen)(H2O)] was the most active scavenger among the compounds. The compounds have also exhibited noteworthy in vitro inhibitory activity against soybean lipoxygenase. UV titration studies of the interaction of the complexes with calf-thymus (CT) DNA have proved the binding to CT DNA with [Mn(μ2-tolf)2(DMF)2]n exhibiting the highest DNA-binding constant (Kb = 5.21 (±0.35) × 10(5) M(-1)). The complexes bind to CT DNA probably via intercalation as suggested by DNA-viscosity measurements and competitive studies with ethidium bromide (EB), which revealed the ability of the complexes to displace the DNA-bound EB.

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Employment of the monoanion of 2,6-diacetylpyridine dioxime (dapdoH2) as a tridentate chelate in palladium(II) and platinum(II) chemistry is reported. The syntheses, crystal structures, spectroscopic and physicochemical characterization, and biological evaluation are described of [PdCl(dapdoH)] (1) and [PtCl(dapdoH)] (2). Reaction of PdCl2 with 2 equivs of dapdoH2 in MeOH under reflux gave 1, whereas the same reaction with PtCl2 in place of PdCl2 gave 2 in comparable yields (70–80%). The divalent metal center in both compounds is coordinated by a terminal chloro group and a N,N′,N″-tridentate chelating (η3) dapdoH– ligand. Thus, each metal ion is four coordinate with a distorted square planar geometry. Characterization of both complexes with 1H and 13C NMR and UV–vis and electrospray ionization mass spectroscopies confirmed their integrity in DMSO solutions. Interaction of the complexes with human and bovine serum albumin has been studied with fluorescence spectroscopy, revealing their affinity for these proteins with relatively high values of binding constants. UV study of the interaction of the complexes with calf-thymus DNA (CT DNA) has shown that they can bind to CT DNA, and the corresponding DNA binding constants have been evaluated. Cyclic voltammograms of the complexes in the presence of CT DNA solution have shown that the interaction of the complexes with CT DNA is mainly through intercalation, which has been also shown by DNA solution viscosity measurements. Competitive studies with ethidium bromide (EB) have revealed the ability of the complexes to displace the DNA-bound EB, suggesting competition with EB. The combined work demonstrates the ability of pyridyl–dioxime chelates not only to lead to polynuclear 3d-metal complexes with impressive structural motifs and interesting magnetic properties but also to yield new, mononuclear 4d- and 5d-metal complexes with biological implications.

The interactions of MnII ions with the nonsteroidal anti‐inflammatory drug sodium diclofenac in the presence of 1,10‐phenanthroline and 2,2′‐dipyridylamine lead to the formation of the trinuclear [Mn3(diclofenac)6(1,10‐phenanthroline)2(MeOH)] (1) and the mononuclear [Mn(diclofenac)2(2,2′‐dipyridylamine)] (2), respectively, which have been characterized by X‐ray crystallography. Three different coordination modes of the diclofenac ligands exist in 1, whereas the bidentate chelating mode is observed in 2. In the initial evaluation of their biological properties and potential applications, the complexes exhibited good binding propensity to human or bovine serum albumin proteins and have relatively high binding constants. The ability of the compounds to scavenge 1,1‐diphenylpicrylhydrazyl, 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid), and hydroxyl radicals was evaluated, and 1 was the most‐effective scavenger among 1, 2, and sodium diclofenac.

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