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

Abstract

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.