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Photo-assisted reduction of nitrous oxide by bio-inspired copper complexes


​Master in Chemistry - Sujet de stage de Master 2
Published on 12 September 2017



Laboratory: Chemistry and Biology of Metals laboratory
Head: Dr. Stéphane Ménage
Name of the team: Bioinorganic Chemistry and Environment (BioCE)
Head of the team: Dr. Stéphane Ménage
Name and quality of the internship’s head: Dr. Stéphane Torelli, PhD, HDR
Address: Bâtiment K’, 17 avenue des martyrs, 38054 Grenoble cedex 9
Phone: 04 38 78 91 07
Master 2: Chemistry for Life Sciences (CLS) - Organic Synthesis (SOIPA)

Photo-assisted reduction of nitrous oxide by bio-inspired copper complexes

Internship's main goals:
The internship aims at preparing bio-inspired copper complexes for nitrous oxide (N2O) reduction and to initiate an original approach that will associate these active complexes with photosensitive subunits as electron suppliers. The latter will have reduction properties adapted to allow photo-induced catalysis. This approach will be first tested at a bimolecular level (Cu catalysts + Ru photo in mixture). In case of success, a covalent Ru-Cu dyad combining both metal ions in a same molecular organic unit will be considered. Reactivity studies will also be undertaken to characterize reaction intermediates.

Educational interests and skills targeted:
This internship will be multidisciplinary. It combines organic synthesis, inorganic and spectroscopic studies. The laboratory has a wide variety of techniques, ranging from UV-Vis-NIR, to EPR via Mössbauer spectroscopies. It offers a broad view of what is being done in the laboratory. Some experiments will be carried out under an inert atmosphere. The candidate will therefore be sensitized to these particular manipulations.

Abstract:
Nitrous oxide reductase (N2Or) is a Cu-containing metalloenzyme with a tetranuclear [Cu4S] active center (Figure 1). It catalyzes the 2 electrons reduction of N2O to N2 and H2O. N2O in nowadays considered as a main environmental pollutant due to its propensity to destroy the ozone layer and to promote greenhouse effect. In the laboratory, minimalists bio-inspired dinuclear mixed valence Cu2S (CuIICuI) models have been synthesized and have shown a stoichiometric N2Or activity.1-3 The actual aim is to develop a catalytic version that involves the reduction of the identified final oxidized dicopper (II) species. The electrons needed for this process will be here provided by natural light via sensitization of a Ru(II) chromophore (eq.2). This original approach is also bio-inspired from Nature since photosystem II is capable of converting photon to light in association with water oxidation. Under irradiation, the excited state (RuII*) will perform a reducing quenching of the final CuIICuII center in order to regenerate the active CuIICuI species (equ. 3 and 4). Within the team, such an approach has already shown its interest for oxidation catalysis thanks to copper complexes assisted by a photosensitive Ru center.4

2 Cu2II,I + N2O → 2 Cu2II,II + N2 (1)
RuII + Hν → RuII* (2)
2 RuII* + 2 Cu2II,II→ 2 Cu2II,I + 2 RuIII (3)
RuIII + sacrificial electron donor → RuII (4)
 
 
Figure 1. Active sites of the NuOr (CuZ* on the left and CuZ on the right). Green: copper; red: oxygen; yellow: sulfur; blue: nitrogen.

Approaches & material used:
The internship will be based in part on laboratory results. It will be based on the preparation of corresponding mono and dinucleating ligands and the associated mixed valence (II, I) complexes. The trainee will be sensitized to the techniques commonly used in the laboratory (NMR, RPE, UV-Vis, electrochemistry, ...) and will be able, depending on the progresses, to collaborate with partner laboratories. Specific techniques related to the reactivity study (HPLC, GC-MS) will also be discussed.

Technical skills needed :
Organic synthesis, inorganic synthesis, spectroscopy, reactivity studies

Internship’s date:
January to june 2018
In order to meet the deadline for entry to the CEA (3 months for the SPAS), the candidate must present himself as soon as possible.

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Concerning N2Or