Biomimetic Dicopper Architecture for Catalytic Oxygen Activation

Informations projet

BiomCatOx

N° de convention de subvention: 796762

DOI

10.3030/796762

Projet clôturé

Date de signature de la CE 21 Février 2018

Date de début 1 Mars 2018

Date de fin 29 Février 2020

Financé au titre de

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Coût total

€ 175 419,60

Contribution de l’UE

€ 175 419,60

Coordonné par

UNIVERSITAET BERN
Switzerland

Periodic Reporting for period 1 - BiomCatOx (Biomimetic Dicopper Architecture for Catalytic Oxygen Activation)

Période du rapport: 2018-03-01 au 2020-02-29

Résumé du contexte et des objectifs généraux du projet

In the current ecological and economical context (global warming, pollution, waste treatment…) researchers are pushed to develop new industrial processes that are environmental friendly and profitable. In chemistry, syntheses can be very costly in energy, such as the transformation of raw material from natural sources as for example petroleum and gas. Those reactions demand high temperatures and pressure, and conditions that are long and polluting. BiomCatox will develop a new concept for the realization of these reactions in mild conditions, i.e. performing them in water and using dioxygen as a mild oxidant. This will provide a strict control on the reactivity of the process and will improve the efficiency of the synthetic catalyst.
BiomCatOx explored a unique catalyst design for the valorisation of hydrocarbons by oxygen insertion into a C–H bond under mild reaction conditions and using O2 as cheap and benign oxidant. The major challenge that needed to be addressed is the control of the activation of O2 into reactive oxygen species (ROS) for selective and catalytic insertion of an oxygen atom into a C–H bond. The key concept of BiomCatOx was to rigorously control the activation of O2 and the formation of metal-based reactive oxygen species (ROS) to accomplish selective and catalytic oxidation of hydrocarbons. The novelty of BiomCatOx lied in the design of the catalyst that consisted in connecting a heavily truncated protein as electron relay for controllable intramolecular electron transfer (IET) to a synthetic oxidation catalyst. The intramolecular electron transfer could be rationally custom-tailored and therefore provides strict control on the reactivity of the catalytic center and on the formation of the ROS.
BiomCatOx used a stepwise approach involving (i) the development of copper-NHC complexes as powerful catalysts for the formation of ROS and hydrocarbon oxidation, (ii) the development of a copper peptide derived from the azurin active site for efficient electron transfer, and (iii) the covalent connection of the two copper sites into a peptide-complex dicopper conjugate for controlled intramolecular electron transfer. The implementation of BiomCatOx provided efficient catalytic systems and fundamental insights into O2 activation, and disclosed a new catalyst design concept. The results of this project provides a new strategy for more economic and more sustainable hydrocarbon oxidation catalysis that will benefit the organometallic and bio-inorganic chemistry communities. New oxidation catalysts were designed, synthetic academics and the chemical industry will gain access to new strategies for C–H bond functionalization by O2 activation.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

The scientific part of the project was separated in 3 work packages that have been run over the 2 years.

Work Package 1: Synthetic copper complexes for oxidation catalysis
During the first period of the project, the focus was on the design of a synthetic copper complex that would allow oxidation reactions to perform under mild and environment friendly conditions. Two lines of research were conducted in parallele in order to maximize the impact.
On one hand, our attention was focused on the comprehension of N-heterocyclic carbenes (NHCs) based copper complexes. Indeed, very few investigations on the influence of NHC ligand on copper(II) had been performed so far. While many information can be found on precious metals, low valence metals and low oxidation states, it was of interest to get insights into the influence of NHC ligands on high oxidation metals such as copper(II). Synthetic NHC-copper(II) complexes were succesfully synthesized and allowed a better understanding of NHC-Cu bonds via a full spectroscopic study. The results were presented at different international conferences (ICBIC, SCF, ISOC) and reported in a peer-reviwed paper (Inorg. Chem. 2019).
On the other hand, another class of ligands was used (PYA) to generate new copper(II) complexes. Through a thorough study, different types of PYA ligands were discriminated as best targets for the preparation of copper(II) complexes for oxidation catalysis. This methodology allowed the establishment of a new procedure for the oxidation of a type of organic compounds, benzylic alcohols, in a more gentle and environment friendly manner than reported so far. Those results will be published in the coming weeks.

Work Package 2: Copper peptide design
First, a peptide mimick of a well known protein was prepared and copper(II) binding was investigated. The results showed that a too flexible peptide couldn't stabilize a metal into the coordination site, such as copper(II). Based on this result, two lines of research were conducted.
We moved to the use of the full protein to study how to modify an active enzyme known to oxidize organic compounds to accelerate its activity. Indeed, many enzymes have been discovered but are rarely used in the industry world due to their sensitivity. We thus studied the modification of selected enzymes with NHC ligands. The pilar of this line of research was the results found in Work Package 1: using the information we previously discovered, NHC ligands were succesfully incorporated into a modified protein which incresead its activity as electron transfer. Those results were communicated through a peer-reviewed paper (Angewandte, 2019) and international conferences (ICBIC, SCF, SOC, SCS).
Since it is anyway easier to synthesize and use peptides instead of proteins, espacially for industrial application, peptides were designed and synthesized where an NHC ligand was incorporated. Different metals could be coordinated to those artificial peptides and the host group is now focusing on the binding of copper.

Work package 3: Synthetic complex into a peptide
Thanks to the results obtained from the 2 first packages, members of the hostgroup are now investigating the incorportion of copper complexes into a peptide scaffold. Application for oxidation catalysis will be considered.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

The impact of this project opens new opportunity for the design of copper(II) systems for oxidation catalysis. On a short term, new catalysts could be implemented in indutrial processes to lower the economic and environmental impact of chemical industries.
Researchers have now more insights into the use of NHC ligands for the preparation of catalysts. Results from the different packages directly accelerated research within the host group, which also has an impact on research performed with international collaborators. Through the different attended conferences and the published articles, the results were broadcasted to a wider scientific audience.

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