Synthesis, characterisation and catalase-like activity of dimanganese(III) complexes of 1,5-bis(5-X-salicylidenamino)pentan-3-ol (X = nitro and chloro)

VERÓNICA DAIER; HERNÁN BIAVA; CLAUDIA PALOPOLI; SERGIU SHOVA; JEAN-PIERRE TUCHAGUES; SANDRA SIGNORELLA

JOURNAL OF INORGANIC BIOCHEMISTRY

Elsevier

Año: 2004 vol. 98 p. 1806 - 1817

0162-0134

The dimanganese(III,III) complexes [MnIII2(5-NO2-salpentO)(m-AcO)(m-MeO)(methanol)2]Y (1: Y = Br, 2a: Y = I, 2b: Y = I3), [MnIII2(5-NO2-salpentO)(m-AcO)(m-MeO)(methanol)(ClO4)] (3) and [MnIII2(5-Cl-salpentO)(m-AcO)(m-MeO)(methanol)2]Br (4), where salpentOH is the symmetrical Schiff base ligand 1,5-bis(salicylidenamino)pentan-3-ol, were synthesised and structurally characterized. Complex 2b crystallises in the monoclinic system, space group P21/c, and exhibits Mn···Mn separation of 2.911 Å. This Mn···Mn separation is very close to the other characterized (m-alkoxo)2(m-acetato)MnIII2 complexes of X-salpentOH (X = MeO, Br and H) and reveals that the aromatic substituent has little influence on the geometric parameters of the bimetallic core. A correlation between the electronic character of the different ring substituents, the redox potentials of the dinuclear complexes and their catalase activity was evidenced. Complexes 1-4 show saturation kinetics with [H2O2] and the H2O2 disproportionation involves redox cycling between the MnIII2/MnIV2 levels. The catalytic activity studies show that bound acetate is required for catalase activity and that the acetato and alkoxo bridges serve as internal bases facilitating the proton transfer coupled to oxidation of the metal centre.