A new proton anisotropic-isotropic shift correlation experiment is described which operates with ultrafast MAS, resulting in good resolution of isotropic proton shifts in the detection dimension. The new experiment makes use of a recoupling sequence designed using symmetry principles which reintroduces the proton chemical shift anisotropy in the indirect dimension. The experiment has been used to measure the proton shift tensor parameters for the OH hydrogen-bonded protons in tyrosine.HCl and citric acid at Larmor frequencies of up to 850 MHz.

A new 19 F anisotropic-isotropic shift correlation experiment is described that operates with ultrafast MAS, resulting in good resolution of isotropic 19 F shifts in the detection dimension. The new experiment makes use of a recoupling sequence designed using symmetry principles that reintroduces the 19 F chemical shift anisotropy in the indirect dimension. The situations in which the new experiment is appropriate are discussed, and the 19 F shift anisotropy parameters in poly(difluoroethylene) (PVDF) are measured. In addition, similar recoupling sequences are shown to be effective for measuring 1 H -19 F distances via the heteronuclear dipolar interaction. This is demonstrated by application to a recently synthesized zirconium phosphonate material that contains one-dimensional chains linked by H -F hydrogen bonds.

A 1 H anisotropic-isotropic chemical shift correlation experiment which employs symmetry-based recoupling sequences to reintroduce the chemical shift anisotropy in ν1 and ultrafast MAS to resolve 1 H sites in ν2 is described. This experiment is used to measure 1 H shift parameters for L-ascorbic acid, a compound with a relatively complex hydrogen-bonding network in the solid. The 1 H CSAs of hydrogen-bonded sites with resolved isotropic shifts can be extracted directly from the recoupled lineshapes. In combination with DFT calculations, hydrogen positions in crystal structures obtained from X-ray and neutron diffraction are refined by comparison with simulations of the full two-dimensional NMR spectrum. The improved resolution afforded by the second dimension allows even unresolved hydrogen-bonded sites 1 H to be assigned and their shift parameters to be obtained.