Hydrogenation clusters

For the Fe-S proteins, the frequencies and sulfur Isotope dependence of the Fe-S vibrational inodes can be used to distinguish mononuclear, blnuclear, and tetranuclear clusters. Hydrogen bonding of both Fe-0 and Fe-S clusters can be detected by frequency shifts in deuterium-substituted proteins. 

G. Pino, G. Gregoire, C. Dedonder-Lardeux, C. Jouvet, S. Matrenchard and D. Solgadi, A forgotten channel in the excited state dynamics of phcnol-(am mon ia)n clusters hydrogen transfer, Phys. Chem. Chem. Phys., 2 (2000) 893-900. 

Si [91] Adsorption at dimer bridge site forming SiH2 clusters. Hydrogen on surface changes the growth mode in comparison to the clean surface. 

Figure 2 The optimized geometries of a Pt4 cluster. Hydrogen adsorbed in the atop position (A) F20 and (B) Na20 support. CH3 adsorbed atop (C) F20 and (D) Na20 support. CH2 adsorbed in the bridged position (E) F20 and (F) Na20 support. The C-H bond length was not affected by the support, the Pt-O and O-X bond lengths were unaffected by the adsorbate. The bondlengths are given in A.

Figure 2.43 (a) [Lns] clusters, hydrogen atoms have been removed for clarity (b) view of the cluster where ligands have been removed for clarity [77]. (Reproduced from S. Petit, F. Baril-Robert, G. Pilet, C. Reber and D. Luneau, Luminescence spectroscopy of europium(III) and terbium(III) penta-, octa-and nonanuclear clusters with fS-diketonate ligands, Dalton Transactions, 34, 6809-6815, 2009, by permission of the Royal Society of Chemistry.)... 

Reaction conditions Presence of Ag s+ cluster Hydrogen effect on HC-SCR Reference... 

S26.6 Hydrogen bonding and replacement of one cysteine with a histidine should lead to an increase in the reduction potential of an Fe-S cluster. Hydrogen bonding should stabilize the more reduced, electron-rich oxidation level of an Fe-S cluster. Two HiS for-Cys substitutions raise the reduction potential in the Rieske centres because... 

H. J. Neusser and K. Siglow, High-resolution ultraviolet spectroscopy of neutral and ionic clusters hydrogen bonding and the external heavy atom effect, Chem. Rev. 100,3921-3942 (2000). Y. Matsumoto, T. Ebata, and N. Mikami, Structures and vibrations of 2-naphthol-(NH3) (n = 1-3) hydrogen-bonded clusters investigated by IR-UV double-resonance spectroscopy, J. Mol. Struct. 552, 257-271 (2000). 

The experimental BDEs in ions, clusters, hydrogen-bonded species, surface-bonded, and van der Waals complexes are essential data for catalysis, high-tech, nano-materials, bioengineering, environmental, and space science however, these valuable data are dispersed throughout a variety of publications. 

Abstract The correct description of the weak interaction between small molecules and oxide surfaces is still a challenge for theory. In the present review, the current status of the cluster approach to the calculation of adsorption geometries and energies by means of quantum-chemical ab initio methods is discussed. In the first part, the physical and chemical contributions to the bonding mechanism are briefly characterized and the different clusters models currently used for treating molecule/surface interactions are presented free clusters, hydrogen saturated clusters and embedded clusters. We continue with a description of the... 

High catalytic activity is exhibited when one unit cell of NHCO is occupied by one (Pt)2 or (Pt)3 cluster. Hydrogen activation is caused by decomposition of H2 molecules to the atomic state with subsequent formation of the hydride complex. Oxidation-reduction titration as well as electron-microscopy measurements show the incorporation of Pd crystallites inside nylon grains [114]. Most have a mean diameter of about 30 A. However, under the assumption that all the metal is located on the polymeric support surface, the calculated accessible metal surface amounts to several hundred Angstroms. Therefore, during preparation of the Pd-nylon catalyst, part of the metal penetrates into the organic matrix. 

MAS) is an invaluable approach for observing local silicon environments on the silica surface. H NMR approaches distinguish clustered (hydrogen-bonded) and isolated surface silanols. Correlations between Si and H NMR behaviors in silicas have led to detailed structural models of the silica surface based on intersections of OH-terminated 100 and 111 faces of -cristobalite. Other nuclides (e.g., H, C,... 

The cyclic succession of reactions with self repair of the catalyst is illustrated for the catalytic reaction in which sulftu- is removed from thiophene with hydrogen. The successive reaction steps are shown for an Ni3S2 cluster in Fig. 8.1. Thiophene adsorbs on the vacant Ni site of the Ni3S2 complex. Hydrogen can dissociate on the 382 cluster and weaken the Ni-S bonds in the cluster. Hydrogen can subsequently add to the carbon-sulfur bond in thiophene, thus enhancing the C-S bond-breaking reaction. When the reaction is concluded, butadiene and H2S desorb and the 382 particle is restored... 

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