Synthesis, structure and properties of an imidazolate bridged copper, zinc binuclear complex:A model compound for Cu,Zn-SOD

Abstract A new imidazolate bridged Cu 2+ , Zn 2+ binuclear complex [(dtma) CuImZn (dtma)]ClO 4 · 2.5H 2 O taken as an active site model for Cu,Zn-SOD has been synthesized and its crystal structure has been determined. All the bond lengths, bond angles and the distance between copper and zinc atoms in the CuImZn core of the model complex are close to those in Cu,Zn-SOD. ESR parameters of the model complex as a function of pH show that the imidazolate bridge is stable in the pH range 10–12, and is broken on the zinc side at pH ∼ 9. With decreasing pH, the imidazole is released at pH ∼ 4 and the dtma ligand dissociates from the copper-containing fragment at pH ∼ 2.4.