Tuesday, August 08, 2006

MRC: 71Ga NMR; Grandinetti

Magnetic Resonance in Chemistry
Vol: 44, Issue: 9, September 2006
pp. 823 - 831

Title: Solid-state NMR characterization of 69Ga and 71Ga in crystalline solids
Authors: Ash, Jason T.a; Grandinetti, Philip J.a
Affiliations: a. Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, Ohio 43210‐1173, USA
Keywords: gallium NMR; quadrupolar nuclei
Abstract (English):

Gallium model systems containing four- and six-coordinate gallium sites have been investigated using solid-state NMR. Measurement of the isotropic chemical shift and electric field gradient (EFG) have been performed at 9.4 T on a-Ga2O3, b-Ga2O3, LiGaO2, NaGaO2, KGaO2, Ga2(SO4)3, and LaGaO3 using a variety of techniques on both NMR active nuclei (69Ga and 71Ga) including static, high speed magic-angle spinning (MAS), satellite transition (ST) spectroscopy, and rotor-assisted population transfer (RAPT). The chemical shift is found to correlate well with the coordination number, with four-coordinate gallium having values of approximately 50 ppm and six-coordinate gallium having values near 225 ppm (referenced to 1 M gallium nitrate solution). The magnitude of the EFG is found to be correlated to the distortion of the gallium polyhedra, with the strained systems having EFGs of 3 × 1021 Vm-2 or more, while the less strained systems have values of 1.5 × 1021 Vm-2 or less. A plot of chemical shift versus EFG suggests that solid-state NMR of gallium oxyanions can be more discriminating than liquid state NMR chemical shifts alone. Copyright © 2006 John Wiley & Sons, Ltd.

No comments: