A new mixed-valence Mn(II)Mn(III) compound with catalase and superoxide dismutase activities

• Verfasst von: Costa, Rafael O. [VerfasserIn]
• Verfasst von: Comba, Peter [VerfasserIn]
• Verfasst von: Roberts, Asha E. [VerfasserIn]
• Titel: A new mixed-valence Mn(II)Mn(III) compound with catalase and superoxide dismutase activities
• Verf.angabe: Rafael O. Costa, Sarah S. Ferreira, Crystiane A. Pereira, Jeffrey R. Harmer, Christopher J. Noble, Gerhard Schenk, Roberto W.A. Franco, Jackson A.L.C. Resende, Peter Comba, Asha E. Roberts, Christiane Fernandes and Adolfo Horn Jr.
• E-Jahr: 2018
• Jahr: 05 November 2018
• Umfang: 18 S.
• Illustrationen: Diagramme
• Fussnoten: Gesehen am 01.07.2019
• Titel Quelle: Enthalten in: Frontiers in Chemistry
• Ort Quelle: Lausanne : Frontiers Media, 2013
• Jahr Quelle: 2018
• Band/Heft Quelle: 6 (2018) Artikel-Nummer 491, Seite 1-18, 18 Seiten
• ISSN Quelle: 2296-2646
• DOI: doi:10.3389/fchem.2018.00491
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: Catalase
• Sach-SW: mix-valent manganese
• Sach-SW: polymeric manganese
• Sach-SW: reaction mechanism
• Sach-SW: Superoxide Dismutase
• Sach-SW: Tripodal ligand
• K10plus-PPN: 166815269X

Abstract

The synthesis, X-ray molecular structure, physico-chemical characterization and dual antioxidant activity (catalase and superoxide dismutase) of a new polymeric mixed valence Mn(III)Mn(II) complex, containing the ligand H2BPClNOL (N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chlorophenyl)(2-hydroxy)] propylamine) is described. The monomeric unit is composed of a dinuclear Mn(II)Mn(III) moiety, [Mn(III)(μ-HBPClNOL)(μ-BPClNOL)Mn(II)(Cl)](ClO4)2H2O, 1, in which the Mn ions are connected by two different bridging groups provided by two molecules of the ligand H2BPClNOL, a phenoxide and an alkoxide group. In the solid state, this mixed valence dinuclear unit is connected to its neighbors through chloro bridges. Magnetic measurements indicated the presence of ferromagnetic (J = +0.076(13) cm-1) and antiferromagnetic (J = -5.224(13) cm-1) interactions. The compound promotes O2• dismutation in aqueous solution (IC50 = 0.370 µmol dm-3, kcat = 3.6x106 M-1 s-1). EPR studies revealed that a high-valent Mn(III)-O-Mn(IV) species is involved in the superoxide dismutation catalytic cycle. Complex 1 shows catalase activity only in the presence of a base, e.g. piperazine or trimethylamine. The kinetic studies were carried out employing two different methods, resulting in kcat values of 0.58±0.03 s-1 (detection of O2 production employing a Clark electrode) and 2.59±0.12 s-1 (H2O2 consuption recorded via UV-Vis) . EPR and ESI-(+)-MS studies indicate that piperazine induces the oxidation of 1, resulting in the formation of the catalytically active Mn(III)-O-Mn(IV) species.