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  • Publication
    Accès libre
    Superparamagnetic Core-Shell-Type Fe3O4/Ru Nanoparticles as Catalysts for the Selective Hydrogenation of an Unconstrained α,β-Unsaturated Ketone
    (2012)
    Khan, Farooq-Ahmad
    ;
    Superparamagnetic core-shell-type Fe3O4/Ru nanoparticles (particle size ca. 15 nm) synthesized by co-precipitation, adsorption and reduction methods were found to selectively hydrogenate the carbon-oxygen double bond in trans-4-phenyl-3-penten-2-one (conversion 100 %, selectivity > 90 %) with a catalytic turnover of 900 under mild reaction conditions (30 °C, 15 bar H2). The finely dispersed catalyst can be separated from the reaction mixture by using an external magnet, recycled, and reused without significant loss of activity and selectivity.
  • Publication
    Accès libre
    Metallic ruthenium nanoparticles derived from arene ruthenium complexes: synthesis, characterization and applications
    (2012)
    Khan, Farooq-Ahmad
    ;

    The present work deals with the preparation of ruthenium nanoparticles using an organometallic approach. In the first part, the synthesis of ruthenium nanoparticles stabilized by mesogenic isonicotinic ester ligands is presented. We have been interested in the use of long-chain isonicotinic esters as lipohilic components in order to increase the anticancer activity of arene ruthenium complexes, while using them as stabilizers for ruthenium nanoparticles with the aim of exploring self-organization and biological (anticancer) properties of these new hybrid materials. The ruthenium nanoparticles thus obtained as well as their organometallic precursors showed anticancer activity comparable to cisplatin or superior to cisplatin in the cancer cell lines A2780 and cisplatin-resistant cell line A2780cisR, the highest cytotoxicity being 0.179 µM, a value 9 fold lower than cisplatin – a platinum-based chemotherapy drug widely used to treat different types of cancers.

    In second part, silicate-supported ruthenium nanoparticles with a special emphasis on hectorite-supported Ru(0) is presented. Size- and shape-selective preparation of hectorite-supported ruthenium nanoparticles was achieved by using either molecular hydrogen or solvothermal reduction route employing different organometallic precursors. The catalytic efficiency of these nanoparticles was evaluated for different arenes, furfuryl alcohol and α,β-unsaturated ketones. Hectorite-supported ruthenium nanoparticles were found to be promising hydrogenation catalysts. It was observed that the modification of intercalated particles size and reaction conditions tune the catalytic activity for chemo-selective reactions. Thus, these nanoparticles preferentially reduce the C=C olefinic bond in α,β-unsaturated ketones at 35 °C. However, change in particle size results in high selectivity towards C=O bond of α,β-unsaturated ketones, if an excess of solvent is used at low temperatures. A selectivity > 98 % for an unconstrained α,β-unsaturated ketone, trans-4-phenyl-3-penten-2-one, was observed at 0 °C. This kind of selectivity is unique for a heterogeneous catalyst especially when the C=C olefinic bond in α, β-unsaturated moiety is sterically not hindered. It was believed that such a preferential C=O bond hydrogenation in α,β-unsaturated ketones was not possible with heterogeneous catalysts.

    In the last part, superparamagnetic core-shell-type Fe3O4/Ru nanoparticles (particle size ~ 15 nm), synthesized by co-precipitation, adsorption and reduction methods, are presented. Their catalytic efficiency for selective C=O hydrogenation in an unconstrained α,β-unsaturated ketone was evaluated using <>trans-4-phenyl-3-penten-2-one. These particles present a green and sustainable approach towards catalyst separation from the reaction mixture, as they can be efficiently separated from the reaction mixture by applying an external magnetic field.

    It was the aim of this study to develop metallic ruthenium nanoparticles stabilized by mesogenic isonicotinic ester ligands, intercalated in hectorite and supported on magnetite and to evaluate their catalytic and biological potential.
  • Publication
    Accès libre
    Highly selective low-temperature hydrogenation of furfuryl alcohol to tetrahydrofurfuryl alcohol catalysed by hectorite-supported ruthenium nanoparticles
    (2011)
    Khan, Farooq-Ahmad
    ;
    Vallat, Armelle
    ;
    Metallic ruthenium nanoparticles intercalated in hectorite (particle size ~ 4 nm) were found to catalyse the hydrogenation of furfuryl acohol to give tetrahydrofurfuryl alcohol in methanolic solution under mild conditions. The best results were obtained at 40 °C under a hydrogen pressure of 20 bar (conversion 100%, selectivity > 99%). After a total turnover number of 1423, the hectorite supported ruthenium nanoparticles are deactivated but can be recycled and regenerated.
  • Publication
    Accès libre
    Synthesis and Anticancer Activity of Long-Chain Isonicotinic Ester Ligand-Containing Arene Ruthenium Complexes and Nanoparticles
    (2010) ;
    Khan, Farooq-Ahmad
    ;
    Juillerat-Jeanneret, Lucienne
    ;
    Dyson, Paul J.
    ;
    Renfrew, Anna K.
    Arene ruthenium complexes containing long-chain N-ligands L1 = NC5H4–4-COO–C6H4–4-O–(CH2)9–CH3 or L2 = NC5H4–4-COO–(CH2)10–O–C6H4–4-COO–C6H4–4-C6H4–4-CN derived from isonicotinic acid, of the type [(arene)Ru(L)Cl2] (arene = C6H6, L = L1: 1; arene = p-MeC6H4Pr i , L = L1: 2; arene = C6Me6, L = L1: 3; arene = C6H6, L = L2: 4; arene = p-MeC6H4Pr i , L = L2: 5; arene = C6Me6, L = L2: 6) have been synthesized from the corresponding [(arene)RuCl2]2 precursor with the long-chain N-ligand L in dichloromethane. Ruthenium nanoparticles stabilized by L1 have been prepared by the solvent-free reduction of 1 with hydrogen or by reducing [(arene)Ru(H2O)3]SO4 in ethanol in the presence of L1 with hydrogen. These complexes and nanoparticles show a high anticancer activity towards human ovarian cell lines, the highest cytotoxicity being obtained for complex 2 (IC50 = 2 μM for A2780 and 7 μM for A2780cisR).
  • Publication
    Accès libre
    Highly selective C = C bond hydrogenation in α,β-unsaturated ketones catalyzed by hectorite-supported ruthenium nanoparticles
    (2010)
    Khan, Farooq-Ahmad
    ;
    Vallat, Armelle
    ;
    Metallic ruthenium nanoparticles intercalated in hectorite (particle size ∼7 nm) were found to catalyze the specific hydrogenation (conversion 100%, selectivity > 99.9%) of the carbon–carbon double bond in α,β-unsaturated ketones such as 3-buten-2-one, 3-penten-2-one, 4-methyl-3-penten-2-one. The catalytic turnovers range from 765 to 91,800, the reaction conditions being very mild (temperature 35 °C and constant hydrogen pressure 1–10 bar). After a catalytic run, the catalyst can be recycled and reused without loss of activity and selectivity.
  • Publication
    Accès libre
    Shape- and Size-Selective Preparation of Hectorite-Supported Ruthenium Nanoparticles for the Catalytic Hydrogenation of Benzene
    (2009) ;
    Khan, Farooq-Ahmad
    ;
    Boudon, Julien
    ;
    Spassov, Vladislav
    The cationic organometallic aqua complexes formed by hydrolysis of [(C6H6)2RuCl2]2 in water, mainly [(C6H6)Ru(H2O)3]2+, intercalate into white sodium hectorite, replacing the sodium cations between the anionic silicate layers. The yellow hectorite thus obtained reacts in water with molecular hydrogen (50 bar, 100 °C) to give a dark suspension containing a black hectorite in which large hexagonally shaped ruthenium nanoparticles (20–50 nm) are intercalated between the anionic silicate layers, the charges of which being balanced by hydronium cations. If the reduction with molecular hydrogen (50 bar, 100 °C) is carried out in various alcohols, spherical ruthenium nanoparticles of smaller size (3–38 nm depending on the alcohol) are obtained. In alcohols other than methanol, the reduction also works without H2 under reflux conditions, the alcohol itself being the reducing agent; the ruthenium nanoparticles obtained in this case are spherical and small (2–9 nm) but tend to aggregate to form clusters of nanoparticles. Whereas the ruthenium nanoparticles prepared by reduction of the yellow hectorite in refluxing alcohols without hydrogen pressure are almost inactive, the nanoparticles formed by hydrogen reduction catalyze the hydrogenation of benzene to give cyclohexane under mild conditions (50 °C) with turnover frequencies up to 6500 catalytic cycles per hour, the best solvent being ethanol.