title: Radical intermediates in chloroform reactions over triphenylphosphine-protected Au nanoparticles.
abstract: Reactions of chloroform over triphenylphosphine-protected Au nanoparticles have been studied using electron paramagnetic resonance (EPR) spectroscopy and a spin trapping technique. Two competing reactions, abstraction of hydrogen and halogen atoms, were identified. The hydrogen abstraction reaction showed an inverse kinetic isotope effect. Treatment of nanoparticles with oxidizing or reducing reagents made it possible to tune the selectivity of radical formation from halogen to hydrogen (deuterium) abstraction. Treatment with PbO(2) promoted the deuterium abstraction reaction followed by the loss of nanoparticle activity, whereas treatment with NaBH(4) regenerated the nanoparticle activity towards Cl atom abstraction. X-ray photoelectron spectroscopy showed an increased Au:P ratio upon treatment with oxidizing reagents. This is likely due to the oxidation of some phosphine ligands to phosphine oxides which then desorb from the nanoparticle surface.
authors.affiliation: Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom.
authors.forename: Marco
authors.initials: M
authors.lastname: Conte
authors.forename: Karen
authors.initials: K
authors.lastname: Wilson
authors.forename: Victor
authors.initials: V
authors.lastname: Chechik
mesh_terms: D002725:Chloroform / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D009943:Organophosphorus Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D013499:Surface Properties
chemical_list: D005609:Free Radicals; D009943:Organophosphorus Compounds; C061896:triphenylphosphine; D006046:Gold; D002725:Chloroform