| Summary: | 碩士 === 國立臺灣師範大學 === 化學系 === 101 === In order to mimic the active site of MnSOD, a C2-symmetric N3O2 pentadentate ligand, H2BDPP prepared previously by our lab, was deprotonated and employed to react with MnCl2 to give a five-coordinate Mn(BDPP) (1). Complex 1 can be oxidized to form stable MnIII complexes, Mn(BDPP)(OH) (2), Mn(BDPP)(Cl) (3) and [Mn(BDPP) (H2O)](BF4) (4), which are characterized by UV/vis spectroscopy, X-ray crystallography and cyclic voltammetry. The reductive potential for dismutasing superoxide anion should be between −0.24 and +0.96 V (vs. Ag/Ag+), and preferentially near the middle of this range for one-electron oxidation and reduction of superoxide. The reductive potential of complexes 1 and 4 were +0.125 and −0.3 V, respectively. They have the potential to react with KO2. When complex 1 reacted with KO2 at −80 ˚C, three electronic absorptions (λmax = 370, 447, 720 nm) were observed. The UV/vis spectrum of the reaction mixture is similar to that of MnIII-OOH intermediate. According to the proposed MnSOD catalytic cycle, MnIII-OOH intermediate is certainly involved in the catalytic cycle. On the other hand, when complex 4 reacted with KO2 at room temperature, a UV/vis spectrum similar to that of complex 2 was obtained. We proposed that complex 4 was deprotonated by KO2 to form complex 2.
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