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

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

JOURNAL OF INORGANIC BIOCHEMISTRY

ELSEVIER SCIENCE INC

Año: 2004 vol. 98 p. 1806 - 1817

0162-0134

The dimanganese(III,III) complexes 1⁄2MnIII ð5-NO2 -salpentOÞðl-AcOÞðl-MeOÞðmethanolÞ2 ŠY (1: Y = Br, 2a: Y = I, 2b: Y = I3), 2 1⁄2MnIII ð5-NO2 -salpentOÞðl-AcOÞðl-MeOÞðmethanolÞðClO4 ފ (3) and 1⁄2MnIII ð5-Cl-salpentOÞðl-AcOÞðl-MeOÞðmethanolÞ2 ŠBr (4), 2 2 where salpentOH is the symmetrical Schiff base ligand 1,5-bis(salicylidenamino)pentan-3-ol, were synthesised and structurally char- ̊ acterized. Complex 2b crystallises in the monoclinic system, space group P21/c, and exhibits MnÁ Á ÁMn separation of 2.911 A. This III MnÁ Á ÁMn separation is very close to the other characterized ðl-alkoxoÞ2 ðl-acetatoÞMn2 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 MnIII =MnIV levels. The catalytic activity studies show that bound acetate is required for catalase activity and that the 2 2 acetato and alkoxo bridges serve as internal bases facilitating the proton transfer coupled to oxidation of the metal centre.