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Jordan Mangue

Bio-inspired copper complexes syntheses for catalytic nitrous oxide and dioxygen reduction

Published on 5 December 2018

Thesis presented December 05, 2018

N2O is the third most important global warming gas and one of the most aggressive gas against ozone layer. A bio-inspired approach from N2Oreductase (N2Or), enzyme catalysing the two electron reduction of N2O with a four sulfur-bridged copper ions centre, helps for the design of new systems. Six mixed valent copper complexes containing the minimum Cu2(µ-S) core were then synthetized. It has been shown that these structures are affected by solvents in solution. Indeed, in a non-coordinating solvent like acetone, all these complexes have an intermetallic bond and a delocalized valence at room temperature. However in a coordinating solvent, the acetonitrile coordination makes it impossible to form a Cu-Cu bond and localize the valences.
To test the N2Or activity, a prototype allowing a constant N2O bubbling in a UV cuve using a closed system was designed. The aim is to develop a catalytic reduction using sacrificial reductant and proton source. However, the gas bottle used for activity tests seems to contain a small amounts of O2 preventing results interpretation. The aim is now to optimize the prototype by adding a system that can purify N2O before activity tests.
In a second time, the O2 reduction using two electrons to produce H2O2 (a soft oxidant) or four electron to produce H2O (useful in fuel cells) are of interest. It has been shown that all these new complexes are capable of catalytically reducing O2 in acetone using sacrificial electron donors and that only the one without exchangeable position can do it in acetonitrile. The latter has also demonstrate its ability to change its selectivity to produce H2O2 or H2O by changing the sacrificial reductant concentration. These results bring interesting insights for O2 activation with bio-inspired copper complexes.

Bio-inorganic chemistry, bio-inspiration, catalysis, dioxygen, nitrous oxide, copper

On-line thesis.