Dipolar SASS NMR spectroscopy: Separation of heteronuclear dipolar powder patterns in rotating solids

Abstract

Two‐dimensional sample‐spinning NMR techniques for separately obtaining heteronuclear dipolar powder patterns of chemically distinct nuclei are proposed, which involve switching the spinning axis on and off the magic angle. Procedures for the computation of dipolar spectra obtained by this method are described, and various features of such spectra are discussed using simulated spectra. Practical applications of this method are demonstrated with 1 3C spectra of calcium formate, β‐quinol‐methanol clathrate, and urea‐t r a n s‐4‐octene clathrate, providing information on the absolute sign and magnitude of the indirect dipolar couplings, 1 3C–1H distances, and dynamics of trapped molecules in clathrates.