Adsorption of activated ketones on platinum and their reactivity to hydrogenation: a DFT study

Vargas, Ângelo

doi:10.1016/j.jcat.2003.12.006

Cited by 72 publications

(41 citation statements)

References 57 publications

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“…[41,42] Further computational details concerning the use of metal clusters to simulate a surface can be found in previous publications. [14,23,15,18,19,12] The simulations of the extended Pt surface, modelled by a Pt slab with PBC, were carried out with the cp2k [43] program package. The selected simulation box shown in Figure 1 contains 144 atoms distributed on four layers (6 6 unit cells) exposing the (111) crystallographic plane.…”

Section: Methodsmentioning

confidence: 99%

“…[22,16] The energetic distinction between bridge and hollow sites was also found to decrease in the same order. [22,16] Other monocyclic aromatic molecules whose adsorption has been investigated by means of first principles calculations are toluene, [23] 1-phenyl-1,2-propanedione, [13] anisole and 3-5-di-substituted anisoles, [14] acetophenone [18] and pyridine. [20] The adsorption of naphthalene on platinum was studied by Morin et al, [17] by means of an extended system model using a plane waves (PW) basis set and PBC.…”

Section: Introductionmentioning

confidence: 99%

“…the combination of vibrational spectroscopy and density functional theory calculations, either using slab calculations [11] or confined metal clusters [12] to describe the metal surface. The adsorption of benzene on PtA C H T U N G T R E N N U N G (111) has been the subject of several previous studies [11][12][13][14][15][16][17][18][19][20][21] which have demonstrated that the bridge(30) adsorption mode is the most stable, and is followed by the hollow(0) mode. The latter is considered only a transient species for low coverages, while it seems to be the predominant species for high coverages.…”

Section: Introductionmentioning

confidence: 99%

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Adsorption of Naphthalene and Quinoline on Pt, Pd and Rh: A DFT Study

et al. 2008

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The adsorption of naphthalene and quinoline on Pt(111), Pd(111) and Rh(111) surfaces is studied using density functional theory. The metal surfaces are simulated by means of large confined clusters and for Pt by means of a slab with periodic boundary conditions (PBC). Calculation parameters such as basis set convergence, basis set superposition error and effects of cluster relaxation and size are analyzed in order to assess the aptness of the cluster model. For all the metals, the preferred sites of adsorption are analyzed, thus revealing their different behaviors concerning structure and stability of adsorption modes. On Pt, the molecules have the richest theoretical configurational variety. Naphthalene and quinoline are found to adsorb preferentially on di-bridge[7] sites on the three metals, and Rh exhibits higher adsorption energies than Pt and Pd. Structural features of the adsorbed molecules are correlated to the calculated adsorption energies. The di-bridge[7] adsorption modes are studied in deeper detail decomposing the adsorption energies in two terms arising from molecular distortion and binding interaction to the metal. Molecular distortion is correlated to the HOMO-LUMO energy gap. The larger adsorption energies found for interactions with Rh result from the lower contribution of the distortion term. Binding interactions are described by analyzing the wave functions of naphthalene and quinoline adsorbed on a subunit of the large clusters in order to reduce the complexity of the analysis. Molecular orbitals are studied using concepts of Frontier Molecular Orbitals theory. This approach reveals that in the adsorption of naphthalene and quinoline on Pt and Pd, an antibonding state lies below the Fermi energy, while on Rh all antibonding states are empty, in agreement with the larger interaction energies. In addition, further insight is gained by projecting the density of states on the d band of the clean surfaces and of the adsorbed systems. This results in the rationalization of the structural features in terms of the concepts of electronic structure theory. The distributions of electronic density are described by means of Hirshfeld charges and isosurfaces of differential electron density. The net electron transfer from the metals to the molecules for most of the sites correlates with the trends of the adsorption energies.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Adsorption of Naphthalene and Quinoline on Pt, Pd and Rh: A DFT Study

et al. 2008

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“…All degrees of freedom of the adsorbed alkaloids were set free to optimize. Several studies dedicated to the adsorption of organic molecules on platinum clusters have pointed out that relaxation of the interacting part of the cluster results in an increase of adsorption energy [29,40,41]. This approximately accounts for the changes induced on a surface by the strong binding of adsorbates.…”

Section: Methodsmentioning

confidence: 99%

“…The bond distance for the platinum was fixed to the experimental value of 2.775 Å for bulk metal [38]. Quinoline, the anchoring moiety of the alkaloid, was initially placed on a double bridge site, in agreement with the finding that bridge sites are the most stable for benzene on a Pt(111) surface [29,39,40]. Since the hollow sites were found to be second in order of stability, double hollow sites were tested in a recent study as possible adsorption sites for CD.…”

Section: Methodsmentioning

confidence: 99%

Towards the engineering of enantioselective properties of supported platinum catalysts

Vargas

Baiker

2006

Molecular Simulation

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Understanding the sub-molecular structure of conformationally complex adsorbed molecules is still a difficult task for experimentalists interested in the structure of modified surfaces, therefore first principles calculations can be a fundamental tool for the investigation of structural details otherwise impossible to identify. Density functional theory (DFT) calculations of the adsorption of cinchonidine (CD) and O-phenyl-cinchonidine (OPhCD) have been performed, using large metal clusters to simulate the metal surface and a zero order regular approximation (ZORA) Hamiltonian to account for relativistic effects due to the heavy nuclei involved. The local geometry of chiral surface sites formed by CD was investigated in detail and discussed in relation to the reaction of enantioselective hydrogenation of activated ketones on cinchona modified platinum. Also, the relevant conformations of OPhCD were investigated and the resulting structure of the chiral sites is discussed and compared to those obtained for the parent alkaloid CD. The adsorption behavior on platinum of a series of substituted anisoles was also investigated, in order to evince the effect that phenyl substitution might have on the relative proportion of surface conformers in substituted OPhCD ethers, that have been shown to possess interesting enantioswitching properties when used as surface modifiers in the enantioselective hydrogenation of activated ketones on cinchona alkaloid modified platinum. A correlation between conformational distribution of the modifiers and the selectivity of the catalyst is proposed.

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