Other Anisotropic NMR Parameters

RDCs are easy to measure and the interpretation with respect to distance and angular information is readily available. Other anisotropic parameters contain similar information, but are either difficult to obtain experimentally or are more complex in terms of interpretation. In the following, a brief introduction into RQCs, RCSA and PCSs is given. 

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RDCs belong to the so-called anisotropic NMR parameters which cannot be observed in isotropically averaged samples as, for example, is the case in liquids. Besides RDCs, a number of other anisotropic parameters can be used for structure elucidation, like residual chemical shift anisotropy, residual quad-rupolar couplings for spin-1 nuclei, or pseudo-contact shifts in paramagnetic samples. Here, we will focus on RDCs where we give a brief introduction into the dipolar interaction, then into the averaging effects with the description by the alignment tensor and concepts to deal with the flexibility of molecules. For the other anisotropic NMR parameters, we refer the reader to ref 19 for an introduction and to refs. 6-8 for a detailed description. 

The NMR data for NMR coesite were derived from the anisotropic dimension of a DAS data set (Figure 6.9, Grandinetti et al. 1995). The NMR parameters for all the other samples were taken from ID static and MAS data. The static measurements of the Si02... 

Brownian motion and hence no quadrupole splitting is observed. A few key references will also be given of selected solid state studies (excluding intermetallics), where there is only a restricted number of other data, or where NMR parameters obtained under anisotropic conditions have been correlated with solution data ( V, Mn). 

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