Hydrogen and Deuterium Atoms in OctasiIsesquioxanes: Experimental and Computational Studies.
The rate of detrapping of atomic hydrogen from several octasilsesquioxanes is the same for dissolved and solid samples and is independent of the presence of other species such as free radicals or oxygen; varying the cage substituents leads to only minor differences in the activation parameters. Hydr...
| Publicado en: | Journal of the American Chemical Society Vol. 128; no. 18; pp. 6111 - 6126 |
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| Autores principales: | , , |
| Formato: | Artículo |
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American Chemical Society
5/10/2006
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| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=21109613&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 21109613 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 5/10/2006 vid: 128 iid: 18 pid: 997 pub: American Chemical Society artinfo: ui: 21109613 10.1021/ja055177d ppf: 6111 ppct: 15 formats: tig: atl: Hydrogen and Deuterium Atoms in OctasiIsesquioxanes: Experimental and Computational Studies. aug: au: Päch, Michael Macrae, Roderick M. Carmichael, Ian affil: Contribution from the Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556 Institute of Chemistry: Metalorganics and Inorganic Materials, Technical University of Berlin, Strasse der 17. Juni 135, Sekr. C2, 10623 Berlin, Germany Department of Natural and Behavioral Sciences, Marian College, Indianapolis, IN 46222 su: Alkanes Hydrogen Atoms Germanium Relaxation phenomena sug: subj: Alkanes Hydrogen Atoms Germanium Relaxation phenomena ab: The rate of detrapping of atomic hydrogen from several octasilsesquioxanes is the same for dissolved and solid samples and is independent of the presence of other species such as free radicals or oxygen; varying the cage substituents leads to only minor differences in the activation parameters. Hydrogen atoms are found to be more strongly stabilized in homosubstituted octasilsesquioxanes compared with singly Ge-substituted cages. A kinetic isotope effect observed for the detrapping of H and D from MeT is ascribed to the difference in the zero-point energies of the trapped atoms. There is a secondary H/D isotope effect in the temperature dependence of the Si-superhyperfine splitting constants in the range 228-353 K. Cage relaxation has a substantial effect on the detrapping barrier but little influence on the intracage potential. Calculations using a rigid cage approximation give satisfactory agreement with zero-point parameters extracted from experimental data. Different model chemistries yield qualitatively different pictures of the dependence of the hyperfine coupling constant of the trapped H atom upon the detrapping coordinate. Within an isotropic approximation of the vibrational displacements, the B3LYP data give fairly close agreement with the experimental temperature dependence, subject to a shift of the absolute value related to known weaknesses of the method. For the SiGe cage, it is found that the transition state in which the H atom passes through a Ge-containing face is strongly favored, accounting for the larger detrapping rate parameters observed experimentally for this species. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2006 holdings: @attributes: islocal: N |
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