23Na NMR study

More recent studies show some variations to the above generalities. 13C and 23Na NMR studies indicate that for Na+ the complexation sequence is 18-crown-6 > 15-crown-5 > benzo-lS-crown-5,482 hinting at the need for ligand flexibility conduction data reveal that for 18-crown-6 the stability sequence is K+>Rb+>Cs+>Na+ 483 extraction studies using metal picrates show that for benzo-15-crown-5, Na+ > K+ > Rb+ > Li+ > Cs+ for 1 1 complexes and that for the corresponding 1 2 complexes K+ > Rb+ > Cs+ 484 further extraction work indicated... 

Sodium octanoate (NaO) forms reversed micelles not only in hydrocarbons but also in 1-hexanol/water. The hydration of the ionogenic NaO headgroups plays an important role in this case too. For this reason Fujii et al. 64) studied the dynamic behaviour of these headgroups and the influence of hydration-water with l3C and 23Na NMR measurements. Below w0 = [H20]/[NaO] 6 the 23Na line-width... 

Besides the 29Si and 27 A1 NMR studies of zeolites mentioned above, other nuclei such as H, 13C, nO, 23Na, 31P, and 51V have been used to study physical chemistry properties such as solid acidity and defect sites in specific catalysts [123,124], 129Xe NMR has also been applied for the characterization of pore sizes, pore shapes, and cation distributions in zeolites [125,126], Finally, less common but also possible is the study of adsorbates with NMR. For instance, the interactions between solid acid surfaces and probe molecules such as pyridine, ammonia, and P(CH3)3 have been investigated by 13C, 15N, and 31P NMR [124], In situ 13C MAS NMR has also been adopted to follow the chemistry of reactants, intermediates, and products on solid catalysts [127,128],... 

Unfortunately however, the cations most often found in natural and synthetic zeolites are not ideal for NMR studies. The 23Na nucleus has a large quadrupolar moment, while cations of most spin j nuclei (such as Y, Rh, Ag, Cd, Pb, Hg, Os, and Pt) are of relatively little interest to the zeolite chemist. For these reasons much attention has been paid to 7Li, which has a small quadrupolar moment, and to 20ST1, an attractive spin 5 nucleus. On the other hand, the 23Na resonance can be used as a sensitive probe for the electric field gradient in zeolites and the effects brought about by sorbed molecules. 

Si 4H CP/MAS-NMR, 27A1 and 23Na MQ/MAS-NMR studies have been made of amorphous aluminium silicates, to determine local atomic struc-tures. A1 MAS-NMR (together with some other nuclei) studies have been carried out on novel porous sodium aluminophosphate-silicate and sodium ammonium fluorophosphates silicate 340 an ordered hexagonal mesoporous silica material (JLU-30) 341 mesoporous Al-MSU-X aluminosilicate 342 cubic mesoporous aluminosilicate A1MB48 343 and mesoporous Al-SBA-15.344... 

A lithium NMR study has been made of lithium atoms adsorbed on a Si(lll)-(3 x 1)-Li surface.634 23Na and 35C1 NMR spectra were used to probe the distribution and state of Na+ and Cl ions in tissues.635... 

The present study uses 23Na NMR to probe ionic mobility, binding, and electronic environment in hydrated Nafion. Data that bear on the development of theoretical models (1,3) are obtained. Preliminary results for other alkali metals and for water of hydration are presented. 

The long-lasting solvates can profitably be viewed as true complexes. On this basis, if two solvents and Lg compete for coordination to the sodium cation, %a chemical shifts and linewidths will be, in the presence of preferential solvation, non-linear functions of the composition of the binary (L + L ) mixture. We observe indeed such curves, deviating strongly from ideality, when the 23Na nmr observables for Na+CIOT are plotted against composition of binary solvent mixtures of THF (as the reference solvent) and various amines unidentate amines studied(6) include aniline, pyridine, pyrrolidine, piperidine, propylamine, and i-propylamine bidentate amines studied(7) are ethylenediamine, diethylenetriamine, 1,3-diamino propane, and cadaverin. 

MAS has been applied to a highly viscous cubic phase of a lyotropic LC formed by 1-monooleolyl-rac-glycerol and water in order to obtain liquid-like and 13C spectra.330 Deuterium, sodium, and fluorine NMR spectroscopy have been applied to study the phase behaviour of several dilute lamellar systems formed by low concentrations of an ra-hexadecylpyridinium salt, a sodium salt (e.g., NaBr, NaCl, or sodium trifluoroacetate), 1-hexanol, and D20.331 The 2H, 19F, and 23Na splittings were used to monitor the phase equilibria. The last two studies are motivated by the search of new lyotropic LC for the alignment of biomolecules. 

---