IQUIR   05412
INSTITUTO DE QUIMICA ROSARIO
Unidad Ejecutora - UE
artículos
Título:
Tuning the MnII 2/MnIII 2 redox cycle of a phenoxo-bridged diMn catalase mimic with terminal carboxylate donors
Autor/es:
DAIER, VERÓNICA; MORENO, DIEGO M.; SOLÍS, VERÓNICA; RIVIÈRE, ERIC; HUREAU, CHRISTELLE; PALOPOLI, CLAUDIA; COLLIN, FABRICE; SIGNORELLA, SANDRA
Revista:
JOURNAL OF INORGANIC BIOCHEMISTRY
Editorial:
ELSEVIER SCIENCE INC
Referencias:
Año: 2018 vol. 182 p. 29 - 36
ISSN:
0162-0134
Resumen:
A new phenoxo-bridged diMnIII complex, Na[Mn2L(OH)2(H2O)2]·5H2O (1), obtained with the ligand L5− = 5‑methyl‑2‑hydroxo‑1,3‑xylene‑α,α‑diamine‑N,N,N′,N′‑tetraacetato, has been prepared and characterized. Mass spectrometry, conductivity, UV?visible, EPR and 1H NMR spectroscopic studies showed that the complex exists in solution as a monoanionic diMnIII complex. Complex 1 catalyzes H2O2 disproportionation with second-order rate constant kcat = 305(9) M−1 min−1 and without a time-lag phase. Based on spectroscopic results, the catalase activity of complex 1 in methanol involves a MnIII 2/MnII 2 redox cycle, which distinguishes this catalyst from other phenoxo-bridged diMn complexes that cycle between MnIIMnIII/MnIIIMnIV species. Addition of base stabilizes the catalyst, restrains demetallation during catalysis and causes moderate enhancement of catalase activity. The terminal carboxylate donors of 1 not only contribute as internal bases to assist deprotonation of H2O2 but also favor the formation of active homovalent diMn species, just as observed for the enzyme.