title: Size-selective catalytic activity of Pd nanoparticles encapsulated within end-group functionalized dendrimers.
abstract: The synthesis and size-selective catalytic activity of Pd nanoparticles encapsulated within dendrimers functionalized with different-sized end groups is described. We designed and synthesized a series of fourth-generation poly(amidoamine) dendrimers having various extents of steric crowding on their periphery. This was accomplished by reacting the terminal amine groups of these dendrimers with epoxyalkanes substituted with different-sized alkyl groups. The modified dendrimers were characterized by 1H NMR, 13C NMR, and matrix-assisted laser desorption ionization mass spectrometry. Nearly monodisperse (1.7 +/- 0.2 nm) Pd nanoparticles were encapsulated within the interior of these dendrimers, and the resulting composite catalysts were used for the hydrogenation of three alpha-allylic alcohols having different sizes. The results showed a clear correlation between the extent of steric crowding on the dendrimer surface and the turnover frequencies (TOFs) for the substrates: more steric crowding on the dendrimer surface led to lower TOFs.
authors.affiliation: Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, USA.
authors.forename: Sang-Keun
authors.initials: SK
authors.lastname: Oh
authors.forename: Yanhui
authors.initials: Y
authors.lastname: Niu
authors.forename: Richard M
authors.initials: RM
authors.lastname: Crooks