Dipolar couplings magic-angle spinning

Fig. 11.2 Solid-state 13C NMR spectra of a powder sample of U-13C-15N-glycine illustrating the broad NMR resonances in the static sample (a) and the effects of magic-angle spinning at 5 kHz (b) and 10 kHz (c). Both the chemicalshielding tensors and the homonuclear dipolar coupling...

Fig. 31. Representative 188-MHz l9F NMR spectra of p-fluoroaniline (top) andp-fluoroni-trobenzene (bottom) obtained in zeolites HY and HZSM-5. Spinning sidebands are denoted by asterisks. Spectra were acquired (several thousand scans) using magic angle spinning (4-mm rotors), cross polarization (2 ms), and proton dipolar coupling. (Reprinted with permission from Nicholas et al. (82). Copyright 1995 American Chemical Society.)...

Fig. 4. Quadrupolar powder patterns (a) Spin NMR powder pattern showing that the central -)<- ) transition is broadened only by dipolar coupling, chemical shift anisotropy, and the second-order quadrupolar interactions, (b) Spin 1 NMR powder pattern for a nucleus in an axially symmetric electric field gradient (see text). The central doublet corresponds to 6 = 90° in Eq. (10). The other features of low intensity correspond to 6 = 0° and 6 = 180°. (c) Theoretical line shape of the ) - -) transition of a quadrupolar nuclear spin in a powder with fast magic-angle spinning for different values of the asymmetry parameter t (IS) ...

We have successfully applied the fluorine probe approach to the estimation of the F-F distance in the microtubule-bound F2-10-Ac-docetaxel (74, SB-T-30021) using the solid-state magic angle spinning (SS MAS) 19F NMR coupled with the radio frequency driven dipolar recoupling (RFDR) technique in our preliminary study.78... 

Spectra of solids arc complicated, because of the multiplicity of parameters involved, especially by anisotropic interactions as dipolar coupling. Many techniques both experimental or computational have been developed for interpretation. A technique particularly useful for catalysis permits to selectively suppress anisotropic contributions by mechanical rotation of the sample (magic angle spinning, MASNMR) and by rotation of the nuclear magnetic dipoles with sequences of radiofrcqucncy pulses. 

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