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Subject of the Master's internship

Theoretical modelling of reaction pathways for small molecule activation

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Published on 3 October 2019
Summary
Our main interest is to understand the mechanism of organic reactions using computer modelling with quantum chemistry approaches. Indeed catalysts involving ecofriendly metal ions such as Fe have been shown to promote new and promising nitrogen or carbene group transfers into organic molecules in one strike. But the mechanism is not fully understood whereas improvements in such reactions are clearly needed. Within such context, theoretical modelling is a powerful tool in conjunction with experimental data to help rationalizing the role of the catalyst. Such understanding is crucial to improve the design of the catalysts. The proposed study is to realize Density Functional Theory (DFT) calculations, a high-level theoretical method, to explore possible molecular species involved in the course of the reaction: the initial molecules, the final products and most importantly the transient species that are generated within the reaction. The calculations will give information on the structures of the species and on their electronic state, and these will be compared to experimental results in order to give a complete picture of the reaction pathway.

Full description of the subject
Nowadays the synthesis of fine chemicals, for health or agrochemical purposes for instance, is facing the challenge of sustainability, with an urge to develop more environment friendly processes. This commitment of green chemistry leads among others, to the development of strategies involving less synthetic steps and an increased use of ecofriendly catalysts. In this context, the development in the last fifteen years of the nitrene transfer reaction (nitrene = R-N group) or of the carbene transfer (carbene = CR1R2) catalyzed by transition metal complexes has open the way to new and easier synthetic routes. Such transfer allows the direct insertion of a nitrogen-group or a carbene group into an organic substrate in one strike, avoiding tedious steps of protection/deprotection. Therefore the understanding of its mechanism is of utmost importance, in order to improve the design of catalysts and broaden the scope of application.
Our team has been involved for several years in the theoretical modelling of such reactions in close collaboration with experimentalists, with two main objectives: i) obtain information by spectroscopic means on the intermediates playing a role in the reaction ii) propose reaction mechanisms with activation barriers and thermodynamic parameters in agreement with experimental catalytic observations.
We propose in this study to explore the mechanism of carbene transfer using Fe catalysts with theoretical methods rooted in the Density Functional Theory approach. Such methods have proven to be very effective in describing reaction mechanisms and spectroscopic signatures (UV-visible or infra-red spectrum, EPR, Mossbauer, …). In this study we will be interested in a bioinspired Fe catalyst which has been shown to promote efficient nitrene or carbene transfers to various organic molecules. One strong advantage is that numerous experimental data on possible intermediates and catalytic parameters have already been obtained. Such experimental inputs will help a lot the modelling and strengthen its reliability. Thus the study will be purely theoretical but will be carried out in close interaction with two experimental teams, one at CEA-Grenoble and one at IRCE-Lyon.
The outcome will be the description of the intermediates involved in the reaction and of the energetics of the reaction consistent with experimental results, in order i) to propose a full picture of the reaction and ii) to propose new route for catalyst improvement.

Requested skills
basic knowledge in physicochemistry on thermodynamics and electronic structure, molecular modelling, computer skills (Linux machines)

Keywords
molecular modelling, reaction mechanism

Contact
Pascale Maldivi - Phone: 04 38 78 53 03