The electronic nature of the metal-metal quadruple bond: variable photon energy photoelectron spectroscopy of Mo2(O2CCH3)4

1992 ◽  
Vol 114 (26) ◽  
pp. 10492-10497 ◽  
Author(s):  
Dennis L. Lichtenberger ◽  
Charles D. Ray ◽  
Frank Stepniak ◽  
Yu Chen ◽  
J. H. Weaver
Keyword(s):  
Photon Energy ◽  
Photoelectron Spectroscopy ◽  
Electronic Nature ◽  
Quadruple Bond ◽  
Metal Metal

The electronic nature of the –Pn Pn– derivatives (Pn=P/As). New insight, in the light of UV photoelectron spectroscopy [1]

2001 ◽  
Vol 595 (1-3) ◽  
pp. 139-146 ◽  
Author(s):  
Karinne Miqueu ◽  
Jean-Marc Sotiropoulos ◽  
Geneviève Pfister-Guillouzo ◽  
Henri Ranaivonjatovo ◽  
Jean Escudié
Keyword(s):  
Photoelectron Spectroscopy ◽  
Electronic Nature ◽  
Uv Photoelectron Spectroscopy

Mixed Metal Oxide Interfaces: An Experimental and Theoretical Assessment of Secondary Metal Influences in Metal Impregnated Aluminas

1994 ◽  
Vol 368 ◽  
Author(s):  
M. Malaty ◽  
D. Singh ◽  
R. Schaeffer ◽  
S. Jansen ◽  
S. Lawrence
Keyword(s):  
Photoelectron Spectroscopy ◽  
Theoretical Calculations ◽  
Mixed Metal Oxide ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Mixed Metal ◽  
Metal Interactions ◽  
Metal Metal ◽  
Bimetallic System

ABSTRACTStudies of the mixed-metal interface in metal impregnated alumina have indicated the possibility of much metal-metal and metal-substrate interaction. Studies were carried out on NiCu/Al2O3 system which was evaluated to develop a better understanding of the forces that drive modification of the catalytic selectivity of Ni in the presence of Cu. Electron Paramagnetic Resonance (EPR), Powder X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD) and theoretical calculations were carried out on this bimetallic system, using Ni,Ag/Al2O3 as a reference as Ni shows negligible electron perturbation on co-adsorbance with Ag onto alumina. XRD results indicate that gross modification of the electronic fields of Ni and Cu are due to direct coupling and intercalation into the alumina matrix. As a result of this phenomena, these materials may form a good base for the development of novel ceramics based on mixed-metal interactions where the intermetallic perturbations are driven by the substrate effects.

Evidence for the Photoemission Nature of Gd 4f Resonant Photoemission

1998 ◽  
Vol 524 ◽  
Author(s):  
S. R. Mishra ◽  
T. R. Cummins ◽  
W. J. Gammon ◽  
G. D. Waddill ◽  
G. Van der-Laan ◽  
...  
Keyword(s):  
Angular Distribution ◽  
Cross Section ◽  
Photon Energy ◽  
Photoelectron Spectroscopy ◽  
Emission Cross Section ◽  
Linear Dichroism ◽  
Constructive Interference ◽  
Resonant Photoemission ◽  
Magnetic Linear Dichroism ◽  
Spectroscopy Experiment

ABSTRACTThe constructive interference between direct and indirect channels above the absorption threshold of a core level leads to a massive increase in the emission cross section leading to a phenomenon called “resonant photoemission”. Using novel magnetic linear dichroism in angular distribution photoelectron spectroscopy experiment we have tried to understand the nature of the resonant photoemission process in Gd metal. The presence of dichroism in Gd 4f photoemission intensity at a photon energy corresponding to resonant photoemission clearly demonstrates the photoemission-like nature of the resonant photoemission process.

Carbon Supported Pt+Os Catalysts for Methanol Oxidation

2002 ◽  
Vol 57 (2) ◽  
pp. 193-201 ◽  
Author(s):  
Gülsün Gökağaç ◽  
Brendan J. Kennedy
Keyword(s):  
Methanol Oxidation ◽  
Photoelectron Spectroscopy ◽  
Surface Composition ◽  
Carbon Support ◽  
Methanol Oxidation Reaction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Metal Metal ◽  
Metal Support

11% Pt/C, 10% Pt + 1%Os/C, 9% Pt + 2%Os/C, 8% Pt + 3%Os/C, 7% Pt + 4%Os/C, 6% Pt + 5%Os/C and 5%Pt + 6% Os/C catalysts have been prepared for methanol oxidation reaction. Transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and cyclic voltammetry have been used to understand the nature of the species present in these catalysts. 7% Pt + 4% Os/C was the most active catalyst, while 8% Pt + 3% Os/C was the least active one. It is found that the metal particle size and distribution on the carbon support, the surface composition and the oxidation states of the metal particles, the metal-metal and metal support interactions are important parameters to define the activity of the catalyst.

First Examples of Homogeneous Catalytic Cyclotrimerization and Polymerization of Phenylacetylene and Copolymerization of Phenylacetylene and Norbonene with Dinuclear Complexes Containing Unbridged Metal-Metal Quadruple Bond

2003 ◽  
Vol 68 (6) ◽  
pp. 1094-1104 ◽  
Author(s):  
Konstantinos Mertis ◽  
Stavros Arbilias ◽  
Demos Argyris ◽  
Nikos Psaroudakis ◽  
Jiří Vohlídal ◽  
...  
Keyword(s):  
Dinuclear Complexes ◽  
Addition Reactions ◽  
Polymer Yield ◽  
Quadruple Bond ◽  
Metal Metal ◽  
Medium Activity ◽  
Copolymer Structure ◽  
Almost All ◽  
Ligand Addition ◽  
Low Activity

First examples of application of dinuclear complexes containing unbrigded metal-metal quadruple bond as catalysts in cyclotrimerization, oligomerization and polymerization of substituted acetylene are reported. The d4-d4 dinuclear complexes (Bu4N)2[Re2X8] (1) (1a, X = Cl; 1b, X = Br and 1c, X = I) show low activity and the complex [Mo2Cl4(MeOH)2(PPh3)2] (2) medium activity in cyclotrimerization and oligomerization of phenylacetylene (PA). In contrast, the tungsten-based d4-d4, complex Na4[W2Cl8] (3) exhibits high polymerization activity (polymer yield above 90%) and ca 75% cis-selectivity in tetrahydrofuran. The activity and cis-stereoselectivity of these single-component catalysts decrease in the order 3 >> 2 >> 1, which is proportional to the metal-metal quadruple bond propensity towards ligand addition reactions. Complex 3 induces metathesis polymerization of norbornene (NBE) to poly(cyclopentene-1,3-diylvinylene) with 82% cis-selectivity and copolymerization of PA and NBE to almost all-cis high-molecular-weight copolymer containing cyclopentene-1,3-diylvinylene units, which is free of longer sequences of both PA and NBE units. This suggests that also homopolymerization of PA with 3 proceeds by the metathesis mechanism and that the PA/NBE copolymer structure is close to the alternating one.

PHOTOELECTRON SPECTROSCOPY OF SILICON–CARBON CLUSTER ANIONS

1996 ◽  
Vol 03 (01) ◽  
pp. 411-415 ◽  
Author(s):  
A. NAKAJIMA ◽  
T. TAGUWA ◽  
K. NAKAO ◽  
M. GOMEI ◽  
R. KISHI ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Photon Energy ◽  
Photoelectron Spectroscopy ◽  
Carbon Cluster ◽  
Photoelectron Spectra ◽  
Laser Vaporization ◽  
Cluster Anions ◽  
Electron Spectrometer ◽  
Silicon Carbon ◽  
Magnetic Bottle

Photoelectron spectra of [Formula: see text] cluster anions (3≤n, m≤6) were measured at the photon energy of 3.49 eV, by using a magnetic-bottle electron spectrometer having ~60-meV resolution. The [Formula: see text] clusters were produced by laser vaporization of a carbon–silicon mixture rod in a He carrier gas. The spectra of the [Formula: see text] clusters are similar to those of pure [Formula: see text] clusters in the peak positions and their envelopes, which is attributed to the similarity in electronic structure of Si and C atoms, leading to a similar geometry. In contrast, the similarity in the photoelectron spectra is not observed between [Formula: see text] and [Formula: see text] clusters, which is attributed to a change in their geometry; from chain to ring.

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