Hydroxypropyl-α-Cyclodextrin-Capped Palladium Nanoparticles: Active Scaffolds for Efficient Carbon-Carbon Bond Forming Cross-Couplings in Water

Authors

  • Jaqueline D. Senra,

    1. Núcleo de Pesquisas de Produtos Naturais, Universidade Federal do Rio de Janeiro, CCS Bloco H, Cidade Universitária, Rio de Janeiro RJ 21941-614, Brasil
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  • Luiz Fernando B. Malta,

    1. Instituto de Química, Universidade Federal do Rio de Janeiro, CT Bloco A 641, Cidade Universitária, Rio de Janeiro RJ 21941-909, Brasil, Fax: (+55)-21-2562-7559
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  • Marcelo E. H. M. da Costa,

    1. Departamento de Física, Pontifícia Universidade Católica, Rio de Janeiro RJ 22452-970, Brasil
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  • Ricardo C. Michel,

    1. Instituto de Macromoléculas, Universidade Federal do Rio de Janeiro, Rio de Janeiro RJ 21945-970, Brasil
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  • Lúcia C. S. Aguiar,

    1. Núcleo de Pesquisas de Produtos Naturais, Universidade Federal do Rio de Janeiro, CCS Bloco H, Cidade Universitária, Rio de Janeiro RJ 21941-614, Brasil
    2. Instituto de Química, Universidade Federal do Rio de Janeiro, CT Bloco A 641, Cidade Universitária, Rio de Janeiro RJ 21941-909, Brasil, Fax: (+55)-21-2562-7559
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  • Alessandro B. C. Simas,

    1. Núcleo de Pesquisas de Produtos Naturais, Universidade Federal do Rio de Janeiro, CCS Bloco H, Cidade Universitária, Rio de Janeiro RJ 21941-614, Brasil
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  • O. A. C. Antunes

    1. Núcleo de Pesquisas de Produtos Naturais, Universidade Federal do Rio de Janeiro, CCS Bloco H, Cidade Universitária, Rio de Janeiro RJ 21941-614, Brasil
    2. Instituto de Química, Universidade Federal do Rio de Janeiro, CT Bloco A 641, Cidade Universitária, Rio de Janeiro RJ 21941-909, Brasil, Fax: (+55)-21-2562-7559
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    • Deceased on May, 31, 2009


Abstract

A new approach for the preparation of palladium nanoparticles in water from a renewable source, 2-hydroxypropyl-α-cyclodextrin (α-HPCD), which acts both as a reductant and capping agent, is presented. The palladium nanoparticles were characterized by using dynamic light scattering (DLS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), which revealed the formation of spherical particles in the size range of 2–7 nm. Further analysis by Fourier-transform infrared spectroscopy (FT-IR) and 1H NMR did not show covalent bonds between cyclodextrins and palladium nanoparticles, suggesting that α-HPCD is only physically adsorbed on the nanoparticle surface, presumably through hydrophobic interactions which limit the mutual coalescence of nanoclusters. The catalytic activity was tested in Suzuki, Heck and Sonogashira reactions in neat water, providing good yields and selectivities of coupling products under very low Pd loadings (0.5–0.01 mol%). Remarkably, the nanocatalyst showed significant stability hence the aqueous phase remained active for four subsequent runs. The combination of a binding site for substrates (the HPCD cavity) and a reactive centre (Pd core) provides a potential to explore functional catalysis in aqueous medium.

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