Synthesis, characterization and activity of imidazolate-bridged and Schiff-base dinuclear complexes as models of Cu,Zn-SOD. A comparative study

MALLET-LADEIRA, S.; SIGNORELLA, S. R.; RIVIÈRE, E.; HUREAU, C; DAIER, V.; MORENO, D.

JOURNAL OF INORGANIC BIOCHEMISTRY

ELSEVIER SCIENCE INC

Lugar: Amsterdam; Año: 2016 vol. 163 p. 162 - 175

0162-0134

Two imidazolate-bridged diCuII and CuIIZnII complexes, [CuZn(dien)2(μ-Im)](ClO4)3·MeOH (1) and [Cu2(dien)2(μ-Im)](ClO4)3 (2) (Im = imidazole, dien = diethylenetriamine), and two complexes formed with Schiff base ligands, [CuZn(salpn)Cl2] (3) and [Cu2(salbutO)ClO4] (4) (H2salpn = 1,3-bis(salicylidenamino)propane, H3salbutO = 1,4-bis(salicylidenamino)butan-2-ol) have been prepared and characterized. The reaction of [Cu(dien)(ImH)](ClO4)2 with [Zn(dien)(H2O)](ClO4)2 at pH ≥ 11 yields complex 1; at lower pH, the Cu3Zntetranuclear complex [{(dien)Cu(μ-Im)}3Zn(OH2)(ClO4)2](ClO4)3 (1a) forms as the main reaction product. X-ray diffraction of 1a reveals that the complex Contains a metal centered windmill-shaped cation having three blades with a central Zn ion and three peripheral capping Cu(dien) moieties bound to the central Zn ion through three imidazolate bridges. The four complexes are able to disproportionate O2?− in aqueousmedium at pH 7.8, with relative rates 4 N 1 N 2 ≫ 3. [Cu2(salbutO)]+ (4) is the most easily reducible of the four complexes and exhibits the highest activity among the SOD models reported so far; a fact related to the ligand flexibility to accommodate the copper ion in both CuI and CuII oxidation states and the lability of the fourth coordination position of copper facilitating stereochemical rearrangements.