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Nanocatalyseurs hélicoïdaux chiraux à base de polyoxométallates pour les réactions d’oxydation énantiosélectives

Abstract : Chiral polyoxometalates (POMs)-based materials have attracted particular attention in recent years due to their remarkable properties and potential application, especially in the field of catalysis. The goal of this thesis is to design a series of enantiopure nanohelical structures based on polyoxometalates (NANOPOM), for their use as heterogeneous oxidation catalysts. Two approaches were used to prepare these new materials. The first one based on the immobilization of POMs on silica nanohelices and nanoribbons by electrostatic and direct adsorption grafting. These inorganic structures increase the stability and make them less sensitive to external environment. The second approach is to include POM units within the structure of organic nanoribbons and nanohelices during self-assembly of 16-2-16 (L)- or (D)-tartrate gemini amphiphile and POM in water. The characterization of these NANOPOM hybrids by using various techniques such as 31P NMR, UV-Vis, DRIFT, Raman, TEM, HR-TEM and EDX was performed and confirms the structure of these materials, especially the grafting of POM to helical supports. These materials are generally stable, and the induction chirality to the POM anion was confirmed by circular dichroism, highlighting the enantiopurity of these NANOPOM materials. The catalytic properties of these POM hybrids have been tested in the oxidation of sulfides. They are active and recoverable catalysts, unfortunately with no significant enantioselectivity observed in the condition used. We expect that new NANOPOM systems in which POM units are introduced within the structure of nanostructure during gel formation, followed by silica transcription will be more stable, an important feature for their use as recoverable catalyst.
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Mariam Attoui. Nanocatalyseurs hélicoïdaux chiraux à base de polyoxométallates pour les réactions d’oxydation énantiosélectives. Chimie organique. Université de Bordeaux, 2018. Français. ⟨NNT : 2018BORD0447⟩. ⟨tel-02094147⟩

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