| Superoxide is a toxic radical by-product of dioxygen chemistry. Aerobic organisms have built a defense mechanism using superoxide dismutase (SOD) to disproportionate superoxide to dioxygen and hydrogen peroxide. Anaerobic organisms can not tolerate dioxygen and simply reduce superoxide to hydrogen peroxide using superoxide reductase (SOR). The reduction of superoxide by SOR is a proton-dependent process proceeding through a hydroperoxide intermediate. The SOR model complex [FeII(N4SMe2(tren))] + displays reactivity with superoxide and at low temperatures (-78°C) a hydroperoxide intermediate is detected. Kinetic studies of the SOR model complex [FeII(N4SMe2(tren))] + will differentiate between three proposed mechanisms by which the model complex proceeds in the formation of the hydroperoxide intermediate, [FeIII(N4SMe2(tren))OOH]+ . Results indicate superoxide is rapidly protonated in a pre-equilibrium process forming HO2 which then oxidatively adds to [FeII (N4SMe2(tren))]+ forming the intermediate [FeIII(N4SMe2(tren))OOH] +. In addition to reducing superoxide, the SOR model complex [Fe II(N4SMe2(tren))]+ has been found to reduce nitrite to NO in a two-electron, one proton-dependent process where the second electron is from a sacrificial reductant. |
