Hexacoordinate Nickel(II)/(III) Complexes that Mimic the Catalytic Cycle of Nickel Superoxide Dismutase

A functional model complex of nickel superoxide dismutase (NiSOD) with a non‐peptide ligand which mimics the full catalytic cycle of NiSOD is unknown. Similarly, it has not been fully elucidated whether NiSOD activity is a result of an outer‐ or inner‐sphere electron‐transfer mechanism. With this in mind, two octahedral nickel(II)/(III) complexes of a bis‐tridentate N₂S donor carboxamide ligand, N‐2‐phenylthiophenyl‐2′‐pyridinecarboxamide (HL^Ph), have been synthesized, structurally characterized, and their SOD activities examined. These complexes mimic the full catalytic cycle of NiSOD. Electrochemical experiments support an outer‐sphere electron‐transfer mechanism for their SOD activity.