Hydrogen and Deuterium Atoms in OctasiIsesquioxanes: Experimental and Computational Studies.
Saved in:
| Title: | Hydrogen and Deuterium Atoms in OctasiIsesquioxanes: Experimental and Computational Studies. |
|---|---|
| Authors: | Päch, Michael1,2, Macrae, Roderick M.1,3 rmacrae@marian.edu, Carmichael, Ian1 |
| Source: | Journal of the American Chemical Society. 5/10/2006, Vol. 128 Issue 18, p6111-6125. 15p. 2 Diagrams, 10 Charts, 12 Graphs. |
| Subjects: | Alkanes, Hydrogen, Atoms, Germanium, Relaxation phenomena |
| Abstract: | 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 MeT8 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 29Si-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 Si7Ge 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. [ABSTRACT FROM AUTHOR] |
| Copyright of Journal of the American Chemical Society is the property of American Chemical Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
| FullText | Text: Availability: 0 |
|---|---|
| Header | DbId: egs DbLabel: Engineering Source An: 21109613 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
| IllustrationInfo | |
| Items | – Name: Title Label: Title Group: Ti Data: Hydrogen and Deuterium Atoms in OctasiIsesquioxanes: Experimental and Computational Studies. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Päch%2C+Michael%22">Päch, Michael</searchLink><relatesTo>1,2</relatesTo><br /><searchLink fieldCode="AR" term="%22Macrae%2C+Roderick+M%2E%22">Macrae, Roderick M.</searchLink><relatesTo>1,3</relatesTo><i> rmacrae@marian.edu</i><br /><searchLink fieldCode="AR" term="%22Carmichael%2C+Ian%22">Carmichael, Ian</searchLink><relatesTo>1</relatesTo> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Journal+of+the+American+Chemical+Society%22">Journal of the American Chemical Society</searchLink>. 5/10/2006, Vol. 128 Issue 18, p6111-6125. 15p. 2 Diagrams, 10 Charts, 12 Graphs. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Alkanes%22">Alkanes</searchLink><br /><searchLink fieldCode="DE" term="%22Hydrogen%22">Hydrogen</searchLink><br /><searchLink fieldCode="DE" term="%22Atoms%22">Atoms</searchLink><br /><searchLink fieldCode="DE" term="%22Germanium%22">Germanium</searchLink><br /><searchLink fieldCode="DE" term="%22Relaxation+phenomena%22">Relaxation phenomena</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: 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 MeT8 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 29Si-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 Si7Ge 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. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Journal of the American Chemical Society is the property of American Chemical Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
| PLink | https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=egs&AN=21109613 |
| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1021/ja055177d Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 15 StartPage: 6111 Subjects: – SubjectFull: Alkanes Type: general – SubjectFull: Hydrogen Type: general – SubjectFull: Atoms Type: general – SubjectFull: Germanium Type: general – SubjectFull: Relaxation phenomena Type: general Titles: – TitleFull: Hydrogen and Deuterium Atoms in OctasiIsesquioxanes: Experimental and Computational Studies. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Päch, Michael – PersonEntity: Name: NameFull: Macrae, Roderick M. – PersonEntity: Name: NameFull: Carmichael, Ian IsPartOfRelationships: – BibEntity: Dates: – D: 10 M: 05 Text: 5/10/2006 Type: published Y: 2006 Identifiers: – Type: issn-print Value: 00027863 Numbering: – Type: volume Value: 128 – Type: issue Value: 18 Titles: – TitleFull: Journal of the American Chemical Society Type: main |
| ResultId | 1 |
