title: Stabilization of Mn(II) and Mn(III) in mononuclear complexes derived from tridentate ligands with N2O donors: synthesis, crystal structure, superoxide dismutase activity and DNA interaction studies.
abstract: A new family of tridentate ligands PhimpH (2-((2-phenyl-2-(pyridin-2-yl)hydazono)methyl)phenol), N-PhimpH (2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)napthalen-1-ol), Me-PhimpH (2-(1-(2-phenyl-2-(pyridine-2-yl)hydrazono)ethyl)phenol) have been synthesized and characterized. The ligands PhimpH and N-PhimpH after deprotonation react with manganese(II) and manganese(III) starting materials affording [Mn(Phimp)(2)] (1), [Mn(Phimp)(2)](ClO(4)) (2), [Mn(N-Phimp)(2)] (3), [Mn(N-Phimp)(2)](ClO(4)) (4). Complexes [Mn(Phimp)(2)] (1) and [Mn(N-Phimp)(2)] (3) convert to [Mn(Phimp)(2)](+) (cation of 2) and [Mn(N-Phimp)(2)](+) (cation of 4) respectively upon oxidation. Ligand Me-PhimpH stabilized only manganese(III) centre resulting [Mn(Me-Phimp)(2)](ClO(4)) (5). The molecular structures of [Mn(Phimp)(2)], 1 and [Mn(Phimp)(2)](ClO(4)), 2 were determined by single crystal X-ray diffraction. X-ray crystal structures of 1 and 2 have revealed the presence of distorted octahedral MnN(4)O(2) coordination sphere having meridionally spanning ligands. Electrochemical studies for the complexes showed Mn(II)/Mn(III), (E(1/2)=0.14-0.40V) and Mn(III)/Mn(IV), (E(1/2)=0.80-1.06V) couples vs. Ag/AgCl. The redox properties were exploited to examine superoxide dismutase (SOD) activity using Mn(II)/Mn(III) couple. The complexes 1, 2, 4 and 5 have been revealed to catalyze effectively the dismutation of superoxide (O(2)(.-)) in xanthine-xanthine oxidase-nitro blue tetrazolium assay and IC(50) values were found to be 0.29, 0.39, 1.12 and 0.76 microM respectively. DNA interaction studies with complex 2 showed binding of DNA in a non-intercalative pathway. Complexes 1, 2 and 4 exhibited nuclease activity in presence of H(2)O(2) and inhibition of activity was noted in presence of KI.
authors.affiliation: Department of Chemistry, Indian Institute of Technology, Roorkee, Roorkee 247 667, Uttarakhand, India. ghoshfcy@iitr.ernet.in
authors.forename: Kaushik
authors.initials: K
authors.lastname: Ghosh
authors.forename: Nidhi
authors.initials: N
authors.lastname: Tyagi
authors.forename: Pramod
authors.initials: P
authors.lastname: Kumar
authors.forename: Udai P
authors.initials: UP
authors.lastname: Singh
authors.forename: Nidhi
authors.initials: N
authors.lastname: Goel
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry*; D008024:Ligands; D008345:Manganese / Q000737:chemistry*; D015394:Molecular Structure; D009585:Nitrogen Dioxide / Q000737:chemistry*; D013482:Superoxide Dismutase / Q000737:chemistry*; D014131:Trace Elements / Q000737:chemistry
chemical_list: D056831:Coordination Complexes; D008024:Ligands; D014131:Trace Elements; D008345:Manganese; D004247:DNA; D013482:Superoxide Dismutase; D009585:Nitrogen Dioxide