Role of carboxamido nitrogen in mononuclear manganese complex: Superoxide scavenging activity and nuclease activity

Three new ligands Pyimpy (2-((2-phenyl-2-(pyridin-2-yl)hydazono)methyl)pyridine), Me-Pyimpy (1-phenyl-1-(pyridin-2-yl)-2-(1-(pyridin-2-yl)ethylidene)hydrazine) and PampH (N′-phenyl-N′-(pyridin-2-yl)picolinohydrazide) were synthesized. Hexa-coordinated mononuclear complexes [Mn(Pyimpy)2](ClO4)2 (1), [Mn(Me-Pyimpy)2](ClO4)2 (2), and [Mn(Pamp)2](ClO4)·CH3OH, (3·CH3OH) were synthesized and characterized. The molecular structure of [Mn(Pamp)2](ClO4)·CH3OH, (3·CH3OH) was determined by single crystal X-ray diffraction, which afforded distorted octahedral coordination sphere having meridionally spanning ligands. The redox properties were exploited to examine superoxide dismutase (SOD) activity using Mn(II)/Mn(III) couple. The complex 3 having ligands containing carboxamido nitrogen (Nam) donor, has been revealed to catalyze more effectively the dismutation of superoxide (image) ions in xanthine–xanthine oxidase–nitro blue tetrazolium assay as compared to 1 and 2. Among the three complexes, complex 3 was found to be most effective in nuclease activity in the presence of H2O2.