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Solid‐state natural abundance 25 Mg NMR studies of Na 2 MgEDTA·4H 2 O—a possible new reference compound for 25 Mg NMR spectroscopy
Author(s) -
Freitas Jair C. C.,
Wong Alan,
Smith Mark E.
Publication year - 2009
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2328
Subject(s) - chemistry , analytical chemistry (journal) , electric field gradient , quadrupole , coupling constant , nmr spectra database , nuclear magnetic resonance spectroscopy , aqueous solution , chemical shift , spectral line , stereochemistry , atomic physics , physics , organic chemistry , particle physics , astronomy
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.