Solid-State ⁸⁷Sr NMR Spectroscopy at Natural Abundance and High Magnetic Field Strength

Abstract

Twenty-five strontium-containing solids were characterized via (87)Sr NMR spectroscopy at natural abundance and high magnetic field strength (B0 = 21.14 T). Strontium nuclear quadrupole coupling constants in these compounds are sensitive to the strontium site symmetry and range from 0 to 50.5 MHz. An experimental (87)Sr chemical shift scale is proposed, and available data indicate a chemical shift range of approximately 550 ppm, from -200 to +350 ppm relative to Sr(2+)(aq). In general, magnetic shielding increased with strontium coordination number. Experimentally measured chemical shift anisotropy is reported for stationary samples of solid powdered SrCl2·6H2O, SrBr2·6H2O, and SrCO3, with δaniso((87)Sr) values of +28, +26, and -65 ppm, respectively. NMR parameters were calculated using CASTEP, a gauge including projector augmented wave (GIPAW) DFT-based program, which addresses the periodic nature of solids using plane-wave basis sets. Calculated NMR parameters are in good agreement with those measured.

87Sr, 119Sn, 127I Single and {1H/19F}‐Double Resonance Solid‐State NMR Experiments: Application to Inorganic Materials and Nanobuilding Blocks

“…For completeness of the study, the comparison of experimental and GIPAW computed quadrupolar parameters for Sr(PO 3 F) is presented in Table . As already observed for Sr1 in Sr 2 P 2 O 7 (see above), C Q ( 87 Sr) is again overestimated in the case of Sr(PO 3 F) though its order of magnitude is correct (indeed, C Q ( 87 Sr) values can reach huge values, up to ∼ 80 MHz,).…”

“…The 87 Sr NMR spectrum of crystalline Sr 2 P 2 O 7 was characterized by the superposition of two second‐order quadrupolar broadened lineshapes (Figure A). These components were easily distinguished by significant differences in C Q ( 87 Sr), whereas δ iso ( 87 Sr) was not a relevant parameter (as already mentioned in the literature,). The simulated parameters were in rather good agreement with computed data obtained from first principles GIPAW computations [9] (see Table and Figure SI‐4 for 31 P MAS NMR data).…”

“…In other words, the strategy followed here could be related to the acronym DFS VOCS WURST QCPMG. It followed that numerous “difficult” quadrupolar nuclei such as 87 Sr, 127 I, 137 Ba, 209 Bi could be studied at ultra‐high magnetic field with relative ease. Initially, the DFS VOCS WURST QCPMG approach was mainly devoted to the direct single resonance detection of quadrupolar nuclei (apart from { 1 H} decoupling during the acquisition time).…”

Recent progress in solid‐state nuclear magnetic resonance of half‐integer spin low‐γ quadrupolar nuclei applied to inorganic materials

“…[223] (c) Examples of 87 Sr QCPMG NMR spectra from crystalline strontium compounds and (d) the shift ranges for different local strontium coordinations. [224] Reproduced from the respective references with permission of the copyright holder NMR interactions are large creating some wide lines so that the experimental approaches can be steered from an initial understanding of the likely NMR interaction parameters. A key point that emerged quite early from the calculations was that the spectra were dominated by second-order quadrupolar effects, but with some CSA contributions.…”

“…Some example spectra are shown in Figure 15B. [224] There were shift ranges ascribed to different local coordinations (Figure 15C). These two studies reinforced the point made in the 2013 T A B L E 1 0 A compilation of some experimentally determined 87 Sr NMR interaction parameters in inorganic materials that have appeared in the literature since Table 4.4 in Moudrakovski [53] Compound δ iso (ppm)…”