19F NMR of Proton-Containing Solids

Abstract

Using three fluorinated steroids as examples, it is demonstrated that for simple multi-fluorinated organic molecules single-pulse and cross-polarization magic-angle spinning experiments with proton decoupling are both feasible and informative. Spinning sideband manifolds are used to obtain shielding tensor components, and shielding tensor information is also obtained from static lineshape analysis. Dipolar dephasing and rotational resonance effects are illustrated, and fluorine spin–lattice relaxation times have been measured. Spin-diffusion effects are demonstrated for one compound via 2-D spin-exchange experiments. In addition, one compound is shown to exhibit polymorphism. Fluorine-19 solution-state NMR spectral information is also presented, for comparison with the accrued solid-state NMR data.