Sodium cation, nuclear properties

Extraframework cations are needed in anionic zeolites for charge balance, and for several zeolite topologies their locations are well investigated [281, 282]. Different cations have been investigated by solid state NMR in the past with different NMR properties and different project targets. We restrict this section to a tutorial example on sodium cation motion in sodalite and cancrinite structures [283-285], 23Na has a nuclear electric quadrupole moment, and quadrupolar interaction is useful to investigate jump processes, especially when they are well defined. 

Sodium is unlike any other cation in its charge and radius. Thus, sodium must be followed by its own nuclear properties (18). Potassium can be replaced, in principle, by thallium(I) and cesium. Both are useful as they have suitable nuclei for NMR studies but thallium has additionally an absorption band at 214 nm which is very ligand-dependent, a readily observable fiuorescence, and a small temperature-independent paramagnetism which can cause marked shifts in the nuclear resonances of ligand nuclei. We (19) have aimed in the first instance to discover if thalhum replaces potassium eflFectively in enzymes. Table VII shows that it does. 

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