Unraveling the catalytic cycle of redox reactions mediated by metal-based biomimetic complexes through EPR abd NMR spectroscopy

SIGNORELLA, S.

Santa Fe

Workshop; 3rd Workshop on Magnetic Resonance; 2016

FBYCQ - UNL

The special role played by manganese in the redox buffering of living cells results of its unrivaled repertoire of redox chemistry. This redox function of Mn is reflected in the active site of specialized enzyme systems that allow the cell to create an effective defense against oxidative challenges. Manganese catalases (MnCAT) and superoxide dismutases (MnSOD) are among these antioxidant enzymes. Evidence on the effect of the metal environment on the mechanism and oxidation states employed during catalysis has been obtained from studies of low molecular weight MnCAT and MnSOD mimics.1EPR and 1H NMR spectroscopies have proven useful for identifying oxidation states of the metal and the structure of Mn complexes in solution.2 Particularly, in dinuclear systems, EPR is a powerful tool for characterizing the paramagnetic Mn oxidations states that originate from the exchange coupling between the two Mn ions, while 1H NMR is a probe for the nature of the bridging ligand. We have used EPR and 1H NMR spectroscopies to monitor Mn complexes under catalytic conditions in the presence of H2O2 (CAT activity) or O2?- (SOD activity) to characterize the Mn species involved in the catalytic cycle.Mechanistic insights into the catalytic cycle of synthetic models obtained through EPR and 1H NMR studies and their implication in the development of more efficient catalysts will be discussed.