NMR interactions

Table 16. Fluorine-Heteroatom NMR Interactions in the Trifluoromethyl Moiety...

For a receptor concentration of approximately the dissociation constant and a 10-fold excess of ligand Pbomid" 1. he- essentially all receptor molecules are complexed with maximum intensity of the desired NMR interactions. Lower receptor concentrations relative to Ku can be compensated by a higher ligand excess and might be pushed up to a 1000-fold ligand excess [95], but experiments are easiest appUcable with the mentioned 10-20 fold excess. 

An important aspect of all exchange-transferred experiments is the occurrence of nonspecific binding which contributes equally to the NMR interactions in the bound state and carmot easily be distinguished. Nonspecific interaction is best... 

Table 1 NMR interactions in irreducible spherical tensor form ...

All available NMR methods are aimed at the exploitation of the important NMR interactions which contain structural information. The most important interactions are as follows ... 

The main NMR interactions in solution of interest to chemists are the chemical shift relative to some stated standard (6), the indirect coupling constant (7) and the relaxation times T1 (spin-lattice) T2 (spin-spin related to the line width) and T p, the relaxation time in the rotating frame. In the case of solids and oriented samples both the direct dipole-dipole and the electric quadrupole interactions assume greater importance. We shall confine our attention in this chapter to diamagnetic compounds so that we may neglect nuclear interactions with electron spins. 

Samoson and Lippmaa (16) used a two-dimensional NMR technique for the study of half-integer spin quadrupole nuclei in powders, without resorting to MAS. They found that central transition excitation spectra provide a useful means of selective determination of quadrupole interaction parameters in correlation with those describing other NMR interactions. 

Table 5. Summary of solid-state NMR interaction parameters for 14N...

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