Abstract
An N3S2-type Ni(II) complex (8) has been synthesized as a model compound of NiSOD active site, which is coordinated with an amide, an amine, and a pyridyl nitrogens and a thioether sulfur atom in the equatorial positions and with the remaining sulfur weakly bound at the axial position. The UV-vis spectroscopic and electrochemical characterizations of complex 8 showed that the square pyramidal structure was kept in the solution in both the Ni(II) and Ni(III) states. In Ni(III) state, EPR spectrum exhibited a rhombic signal pattern without any hyperfine splittings, indicating no structural change depending on oxidation states. If a protonation to the coordinated thiolate in Cys2 or Cys6 of NiSOD is caused during the oxidative disproportionation process, the thiolate may be kicked up to the axial position because the donor ability of the sulfur has been weakened.
