Solid-State QCPMG NMR of Low-γ Quadrupolar Metal Nuclei in Natural Abundance

Abstract

Taking advantage of an order of magnitude in sensitivity enhancement obtained by sampling of quadrupolar-echo (QE) solid-state NMR spectra during a quadrupolar Carr−Purcell−Meiboom−Gill (QCPMG) pulse sequence, we demonstrate that the coordination environment of low-γ quadrupolar metal nuclei can be studied routinely for powders with these nuclei in natural abundance. The general applicability of the method is demonstrated by 39K, 25Mg, 67Zn, and 87Sr QCPMG solid-state NMR experiments for K2MoO4, KVO3, Mg(VO3)2, Zn(CH3COO)2·2H2O, Zn(Ala)2·H2O, Sr(NO3)2, and SrMoO4. For all samples the quadrupolar coupling parameters and the isotropic chemical shifts are extracted by numerical simulation and iterative fitting of the spin−echo sideband spectra observed in the experimental QCPMG NMR spectra. These parameters are discussed in light of the crystal structures for the compounds.