Electrochemical Reduction of N2O with a Molecular Copper Catalyst

Deoxygenation of nitrous oxide (N2O) has significant environmental implications as it is not only a potent greenhouse gas but is also the main substance responsible for the depletion of ozone in the stratosphere. This has spurred significant interest in molecular complexes that mediate N2O deoxygenation. Natural N2O reduction occurs via a Cu cofactor but there is a notable dearth of synthetic molecular Cu catalysts for this process. In this work, we report a selective molecular Cu catalyst for the electrochemical reduction of N2O to N2 using H2O as a proton source. Cyclic voltammograms show that increasing H2O concentration facilitates deoxygenation of N2O and control experiments with a Zn(II) analog verify an essential role for Cu. Theory and spectroscopy support metal-ligand cooperative catalysis between Cu(I) and a reduced tetraimidazolyl substituted radical pyridine ligand, (MeIm4P2Py = 2,6-(bis(bis-2-N-methylimidazolyl)phosphino)pyridine) which can be observed by Electron Paramagnetic Resonance (EPR) spectroscopy. Comparison with biological processes suggests a common theme of supporting electron transfer moieties in enabling Cu-mediated N2O reduction