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Synthesis and Characterization of Nanocluster Polyoxometalates as Catalysts in Oxidation and Coupling Reactions

Hosseini, Hadigheh Sadat | 2019

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 52443 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Bagherzadeh, Mojtaba
  7. Abstract:
  8. In this study, a series of polyoxometalates nanoclusters is synthesized and their catalytic properties have been investigated in oxidation and coupling reactions. In the first and second sections, {Mo36} nanoclusters are primarily prepared. Then, the mesoporous silica, as a solid surface with a regular chanals and cavities through electrostatic interactions between polyoxo anions and amine functional groups with positive charge, is used to stabilize the nanocluster as well as the final structure of SBA-15-NH3 +•{Mo36}- formed. As a green and environmentally friendly substrate, natural zeolite is used to stabilize the nanoclusters and the {Mo36}@zeolite obtained. Both heterogeneous catalysts show good results in oxidative reactions due to the properties of nano size - materials. In the third section, the {Mo368} nanocluster is used with anionic surfaces as a carrier and stabilizer of palladium nanoparticles. This nanocatalysis (Pd@{Mo368}) show good activity and stability in the Heck reactions in the presence of poly(ethylene glycol) as green a solvent. Nanoparticle size and nanocatalytic activity confirm the optimum interactions between palladium nanoparticles and anionic surface and show the strong impact of the polar stabilizer nature. In the fourth section, a new compond of organic-inorganic hybrid polyoxometalate based on [γ- SiW10O36]8-, with arginine amino acid, is formed by covalent bonding to create an asymmetric environment for the enantiomeric oxidation reactions. Amino acids are one of the compounds that are suitable for synthesis of organic-inorganic hybrid polyoxometalate due to their unique structural properties. The new compound is used for the oxidation of methyl tolyl sulfide to the corresponding sulfoxide. The results showed that the new composite is active in the oxidation reaction and capable to synthesize the asymmetric compound of methyl tolyl sulfoxide. An enantiomeric excces is observed 10% for the new polyoxometalate -arginine compound
  9. Keywords:
  10. Polyoxometalates ; Mesoporous Silica Nanoparticles ; Heck Reaction ; Hybrid Organic-Inorganic Complex ; Enantiomeric Oxidation ; Green Solvent ; Polyethylen Glycol (PEG)

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