Pd-based bimetallic catalysts for parahydrogen-induced polarization in heterogeneous hydrogenations

Production of hyperpolarized catalyst-free gases and liquids by heterogeneous hydrogenation with parahydrogen can be useful for various technical as well as biomedical applications, including in vivo studies, investigations of mechanisms of industrially important catalytic processes, enrichment of nuclear spin isomers of polyatomic gases, and more. In this regard, the wide systematic search for heterogeneous catalysts effective in pairwise H2 addition required for the observation of parahydrogen-induced polarization (PHIP) effects is crucial. Here in this work we demonstrate the competitive advantage of Pd-based bimetallic catalysts for PHIP in heterogeneous hydrogenations (HET-PHIP). The dilution of catalytically active Pd with less active Ag or In atoms provides the formation of atomically dispersed Pd1 sites on the surface of Pd-based bimetallic catalysts, which are significantly more selective toward pairwise H2 addition compared to the monometallic Pd. Furthermore, the choice of the dilution metal (Ag or In) has a pronounced effect on the efficiency of bimetallic catalysts in HET-PHIP, as revealed by comparing Pd-Ag and Pd-In bimetallic catalysts.</p

Crystal structure of phosphonium carboxylate complexes. the role of the metal coordination geometry, ligand conformation and hydrogen bonding

© the Partner Organisations 2014. A series of new mononuclear and heteronuclear complexes of carboxylate phosphonium betaines with biologically important metals (Zn(ii), Cd(ii), Hg(ii) and Cu(ii)) were obtained in aqueous media at ambient temperature. X-ray single crystal diffraction showed that carboxylate phosphonium betaines exhibit versatile complexation abilities, producing monomeric, dimeric and tetrameric homonuclear and mixed metal complexes. The binding mode was found to change in the series of Zn(ii), Cd(ii) and Hg(ii) complexes with an increase of the cation radius. Water and chlorine atoms, bound to the metal, play an important role in crystal formation. In the case of α- and β-substituted phosphabetaines, the crystallization of various stereoisomers was observed including a rare case of co-crystallization of two diastereomers in one crystal. This journal i

A mild post-synthesis oxidative treatment of Pd-In/HOPG bimetallic catalysts as a tool of their surface structure fine tuning

Intermetallic Pd-In particles formation and their deliberate post-synthesis modification by oxidative treatments under carefully controlled conditions have been investigated by the combination of synchrotron radiation-based photoelectron spectroscopy and scanning tunneling microscopy. It is demonstrated that a prolonged contact of Pd-In/HOPG samples with air led to a partial decomposition of intermetallic particles giving rise to the formation of Pd0 species homogeneously distributed over bulk, surface indium hydroxide and subsurface indium oxide. A mild oxidative treatment (0.25 mbar O2, 150 °C) leads to the indium surface segregation and formation of indium oxide homogeneously distributed over the depth and metallic Pd predominantly localized in the interior. The indium oxide component becomes surface localized upon further temperature increase to 200 °C

Crystal structure of phosphonium carboxylate complexes. the role of the metal coordination geometry, ligand conformation and hydrogen bonding

© the Partner Organisations 2014. A series of new mononuclear and heteronuclear complexes of carboxylate phosphonium betaines with biologically important metals (Zn(ii), Cd(ii), Hg(ii) and Cu(ii)) were obtained in aqueous media at ambient temperature. X-ray single crystal diffraction showed that carboxylate phosphonium betaines exhibit versatile complexation abilities, producing monomeric, dimeric and tetrameric homonuclear and mixed metal complexes. The binding mode was found to change in the series of Zn(ii), Cd(ii) and Hg(ii) complexes with an increase of the cation radius. Water and chlorine atoms, bound to the metal, play an important role in crystal formation. In the case of α- and β-substituted phosphabetaines, the crystallization of various stereoisomers was observed including a rare case of co-crystallization of two diastereomers in one crystal. This journal i

La Patrie : journal quotidien, politique, commercial et littéraire

25 février 18671867/02/25 (A27)