Symmetry-based recoupling of 17O–1H spin pairs in magic-angle spinning NMR
Jacco D. van Beek, 1, Ray Dupree and Malcolm H. Levitt
School of Chemistry, Southampton University, Highfield, Southampton, SO17 1BJ, UK
Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
We have performed magic-angle-spinning solid-state NMR experiments in which protons are recoupled to oxygen-17 nuclei by applying a symmetry-based recoupling sequence at the proton Larmor frequency. Two-dimensional quadrupole-dipole correlation spectra are produced, in which the second-order quadrupolar shift of the oxygen-17 central transition is correlated with the recoupled heteronuclear dipole–dipole interaction. These spectra are sensitive to the relative orientation of the electric field gradient at the site of the oxygen-17 nucleus and the O–H internuclear vector. We also demonstrate experiments in which polarization is transferred from protons to oxygen-17, and show that oxygen-17 signals may be selected according to the protonation state of the oxygen site. We discuss the small observed value of the heteronuclear dipolar splitting in the central-transition oxygen-17 spectra.
Keywords: Solid-state NMR; Quadrupolar nuclei; Oxygen-17; Correlation spectroscopy; Symmetry-based recoupling; MAS; Brucite