Synthesis and Characterization of Ni III N3S2 Complexes as Active Site Models for the Oxidized Form of Nickel Superoxide Dismutase

Nickel complexes, [Ni(H 2 BA R TPP)](ClO 4 ) 2 (R=Ph for 1 or i Pr for 2 ), supported by a pentadentate ligand H 2 BA R TPP were synthesized and oxidized to form Ni III species having a N3S2 coordination environment to mimic the active site of the oxidized form of nickel superoxide dismutase (NiSODox). The Ni III species 2 + exhibited a rhombic signal with g  values at 2.15, 2.12 and 2.02 similar to that of NiSODox. DFT calculations revealed that 2 + has an unpaired electron primarily located in the d   z   2orbital of the Ni III center, which strongly overlaps with the p z orbital of the axial pyridine nitrogen of H 2 BA Pr TPP.