Mimicking the reduced, oxidized and azide inhibited form of manganese superoxide dismutase by mononuclear Mn compounds utilizing tridentate ligands

• Published in: Inorganica Chimica Acta 2004-04, Vol.357 (6), p.1695-1702
• Main Authors: Pursche, D, Triller, M.U, Slinn, C, Reddig, N, Rompel, A, Krebs, B
• Format: Article
• Language: English
• Subjects: Crystal structures; Mononuclear manganese complexes; Superoxide dismutase; Tridentate ligands
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2003.10.008

The synthesis and crystal structures of one manganese (II) and two manganese (III) complexes are reported. Novel tridentate ligands were used to mimic the coordination sphere in the oxidized and reduced form of manganese superoxide dismutase. Similar to the enzyme an azide adduct has been obtained and characterized by UV–Vis and IR spectroscopy. The manganese complexes [Mn II(Hbmimpm) 2(NO 3)](NO 3) · Et 2O (1), [Mn III(bmimpm) 2(OAc)] · 2CH 2Cl 2 (2), and [Mn III(bmiapm) 2(OAc)] · MeOH · H 2O · CH 2Cl 2 (3) containing the new ligands Bis(1-methylimidazol-2-yl)-(4-methoxyphen-1-yl)methanol (Hbmimpm) and Bis[(1-methylimidazol-2-yl)](2-aminophenyl)methanol (Hbmiapm) were synthesized. They are good structural models for the reduced ( 1) and oxidized ( 2, 3) form of manganese superoxide dismutase. All complexes were characterized by spectroscopic methods and X-ray structure analysis. Compounds 1 and 2 crystallize in the monoclinic space group P2 1/ c whereas complex 3 crystallizes in the monoclinic space group P2 1/ n. The coordination sphere around the manganese cores is distorted octahedral with two corresponding tridentate ligands representing the protein ligands and one nitrate ( 1) or acetate ( 2, 3) ion occupying two cis positions. Similar to the enzyme the Mn(III) complex 2 reacts with sodium azide. The obtained microcrystalline azide adduct was characterized by UV–Vis and IR spectroscopy.