INQUIMAE   12526
INSTITUTO DE QUIMICA, FISICA DE LOS MATERIALES, MEDIOAMBIENTE Y ENERGIA
Unidad Ejecutora - UE
artículos
Título:
Synthesis, Characterization, and Catalase Activity of a Water-Soluble diMnIII Complex of a Sulphonato-Substituted Schiff Base Ligand: An Efficient Catalyst for H2O2 Disproportionation
Autor/es:
PALOPOLI, C.; BRUZZO, N.; HUREAU, C.; LADEIRA, S.; MURGIDA, D.H.; SIGNORELLA, S.
Revista:
INORGANIC CHEMISTRY
Editorial:
AMER CHEMICAL SOC
Referencias:
Lugar: Washington; Año: 2011 vol. 50 p. 8973 - 8973
ISSN:
0020-1669
Resumen:
A new diMnIII complex, Na[Mn2(3-Me-5-SO3-salpentO)(μ-MeO)(μ-AcO)(H2O)] 3 4H2O (1), where salpentOH = 1,5-bis(salicylidenamino) pentan-3-ol, was synthesized and structurally characterized. The complex possesses a bis(μ-alkoxo)(μ-acetato) triply bridged diMnIII core, the structure of which is retained upon dissolution. Complex 1 is highly efficient to disproportionate H2O2 in an aqueous solution of pH g 8.5 or in DMF, with only a slight decrease of activity. Electrospray ionization mass spectrometry, EPR, and UVvis spectroscopy used to monitor the H2O2 disproportionation in buffered basic medium, suggest that the major active form of the catalyst during cycling occurs in the MnIII2 oxidation state and that the starting complex retains the dinuclearity and composition during catalysis,with the acetate that moves from bridging to terminal ligand. UVvis and Raman spectroscopy ofH2O2 + 1+Bu4NOHmixtures in DMF suggest that the catalytic cycle involves MnIII 2/MnIV2 oxidation levels. At pH 10.6 in an Et3N/Et3NH+ buffer, complex 1 catalyzes dismutation of H2O2 with saturation kinetics on the substrate, first order dependence on the catalyst, and kcat/KM = 16(1) 102 s1 M1. During catalysis, the exogenous base contributes to retain the integrity of the bis(μ-alkoxo) doubly bridged diMn core and favors the formation of the catalystperoxide adduct (low value of KM), rendering 1 a highly efficient catalyst for H2O2 disproportionation.