Solid-state natural abundance 25Mg NMR studies of Na2MgEDTA·4H2O—a possible new reference compound for 25Mg NMR spectroscopy
✍ Scribed by Jair C. C. Freitas; Alan Wong; Mark E. Smith
- Publisher
- John Wiley and Sons
- Year
- 2009
- Tongue
- English
- Weight
- 409 KB
- Volume
- 47
- Category
- Article
- ISSN
- 0749-1581
- DOI
- 10.1002/mrc.2328
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
Natural abundance solid‐state ^25^Mg NMR measurements were made of the disodium salt of magnesium ethylenediaminetetraacetate tetrahydrate (Na~2~MgEDTA·4H~2~O). Both magic angle spinning (MAS) and static experiments were employed to determine the quadrupole coupling constant (C~q~) and the asymmetry parameter (η~q~) of the electric field gradient (EFG) tensor associated with ^25^Mg in this compound, giving the values C~q~ = 1.675(5) MHz and η~q~ = 0.15(1). The isotropic chemical shift was determined to be δ~iso~ = 0.25(10) ppm (relative to 11 M MgCl~2~ aqueous solution) and a small chemical shift anisotropy (CSA) contribution (∼− 13 ppm) was detected, one of the first CSA reports in ^25^Mg NMR. This compound exhibited remarkably good ^25^Mg NMR sensitivity, due to its fast spin‐lattice relaxation and modest quadrupole coupling, which allowed its use as a secondary shift reference and as a test sample for the implementation and optimisation of signal‐enhancement methods in ^25^Mg NMR spectroscopy, such as double frequency sweeps (DFS) and the use of adiabatic hyperbolic secant (HS) and WURST pulses. Copyright © 2008 John Wiley & Sons, Ltd.