Modeling Superoxide Reductase and Superoxide Dismutase Reactivity

The detoxification of superoxide (O2·- ) is managed by iron (Fe) containing metalloenzymes in anaerobic (Fe-SOR) and aerobic (Fe-SOD) organisms by similar pathways: both reduce O2 ·- to hydrogen peroxide (H2O2), but Fe-SOD also oxidizes O2·- to O 2. To understand this selectivity in redox reactivity, a functional SOR, model, [FeII(SMe 2N4-(tren))](BPh4) (1), is tested for O2·- oxidation in an environment that models the active site of SOD. Active site environment effects on Fe catalyzed O2·- oxidation are tested by using a non-coordinating, aprotic, solvent (THF) to replicate the hydrophobic Fe-SOD binding pocket. This work shows that the oxidized Fe-SOR, model [Fe III(SMe2N 4(tren))](BPh4)2 (2) can oxidize O2·- to O2 when the solvent is THF. This reaction can be inhibited with small anions, such as Cl -, indicating an inner-sphere mechanism. The products of the oxidation may include a rare example of an FeIII mu-peroxo dimer observed at room temperature.