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High-resolution 19F MAS NMR spectroscopy: Structural disorder and unusual J couplings in a fluorinated hydroxy-silicate

Griffin, J.M.; Yates, Jonathan R.; Berry, Andrew; Wimperis, Stephen; Ashbrook, Sharon E.

Description

High-resolution 19F magic angle spinning (MAS) NMR spectroscopy is used to study disorder and bonding in a crystalline solid. 19F MAS NMR reveals four distinct F sites in a 50% fluorine-substituted deuterated hydrous magnesium silicate (clinohumite, 4Mg2SiO4· Mg(OD1-xFx)2 with x = 0.5), indicating extensive structural disorder. The four 19F peaks can be assigned using density functional theory (DFT) calculations of NMR parameters for a number of structural models with a range of possible local...[Show more]

dc.contributor.authorGriffin, J.M.
dc.contributor.authorYates, Jonathan R.
dc.contributor.authorBerry, Andrew
dc.contributor.authorWimperis, Stephen
dc.contributor.authorAshbrook, Sharon E.
dc.date.accessioned2015-12-13T22:45:08Z
dc.identifier.issn0002-7863
dc.identifier.urihttp://hdl.handle.net/1885/79611
dc.description.abstractHigh-resolution 19F magic angle spinning (MAS) NMR spectroscopy is used to study disorder and bonding in a crystalline solid. 19F MAS NMR reveals four distinct F sites in a 50% fluorine-substituted deuterated hydrous magnesium silicate (clinohumite, 4Mg2SiO4· Mg(OD1-xFx)2 with x = 0.5), indicating extensive structural disorder. The four 19F peaks can be assigned using density functional theory (DFT) calculations of NMR parameters for a number of structural models with a range of possible local F environments generated by F-/OH- substitution. These assignments are supported by two-dimensional 19F double-quantum MAS NMR experiments that correlate F sites based on either spatial proximity (via dipolar couplings) or through-bond connectivity (via scalar, or J, couplings). The observation of 19F-19F J couplings is unexpected as the fluorines coordinate Mg atoms and the Mg-F interaction is normally considered to be ionic in character (i.e., there is no formal F-Mg-F covalent bonding arrangement). However, DFT calculations predict significant 19F-19F J couplings, and these are in good agreement with the splittings observed in a 19F J-resolved MAS NMR experiment. The existence of these J couplings is discussed in relation to both the nature of bonding in the solid state and the occurrence of so-called "through-space"19F- 19F J couplings in solution. Finally, we note that we have found similar structural disorder and spin-spin interactions in both synthetic and naturally occurring clinohumite samples.
dc.publisherAmerican Chemical Society
dc.sourceJournal of the American Chemical Society
dc.subjectKeywords: Clinohumite; Covalent bonding; Crystalline solids; Density functional theory calculations; DFT calculation; Dipolar couplings; Double-quantum; High resolution; J coupling; Magic angle spinning NMR; Magnesium silicates; MAS NMR; MAS-NMR spectroscopy; Natur
dc.titleHigh-resolution 19F MAS NMR spectroscopy: Structural disorder and unusual J couplings in a fluorinated hydroxy-silicate
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume132
dc.date.issued2010
local.identifier.absfor020400 - CONDENSED MATTER PHYSICS
local.identifier.absfor040200 - GEOCHEMISTRY
local.identifier.ariespublicationf5625xPUB8015
local.type.statusPublished Version
local.contributor.affiliationGriffin, J.M., University of St Andrews
local.contributor.affiliationYates, Jonathan R., University of Oxford
local.contributor.affiliationBerry, Andrew, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationWimperis, Stephen, University of Glasgow
local.contributor.affiliationAshbrook, Sharon E., University of St Andrews
local.description.embargo2037-12-31
local.bibliographicCitation.issue44
local.bibliographicCitation.startpage15651
local.bibliographicCitation.lastpage15660
local.identifier.doi10.1021/ja105347q
local.identifier.absseo970104 - Expanding Knowledge in the Earth Sciences
dc.date.updated2016-02-24T09:39:08Z
local.identifier.scopusID2-s2.0-78649724628
CollectionsANU Research Publications

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