ABSTRACT
The detail and ease of interpretability of a solution nuclear magnetic resonance (NMR) spectrum compared with its solid-state counterpart illustrates why solid-state NMR has long been less widely applied than solution-state methods. The bane and boon of solid-state NMR arise from the same source, the incomplete time averaging of spatially anisotropic phenomena. The most obvious of these is chemical shielding. The other important anisotropic phenomenon that is observed directly in solid-state NMR experiments is dipolar coupling. Much effort in solid-state NMR over the last 20 years has been directed at selectively reintroducing dipolar coupling and detecting polarization transfer between dipolar-coupled nuclei. The efforts to bring the benefits of multinuclear NMR to solid-state NMR have intensified. While the technical difficulties and theoretical complexity of solid-state NMR remain a considerable barrier to the casual user, improvements in hardware and pulse sequences have made it almost inevitable that the next important developments in NMR of complex systems will come in the solid state.
