Solvation from nuclear magnetic resonance

Perhaps the best method for the determination of the solvation numbers of cations in their non-aqueous solutions is nuclear magnetic resonance (NMR) spectroscopy [Sw 62], The procedure is based on the fact that under optimal conditions the NMR absorption band of the coordinated solvent molecules separates from that of the free solvent, and the ratio of the magnitudes of the areas under the two bands provides direct information on the solvation number of the cation. The conditions for the separation of the two NMR signals are that the rate of exchange between the coordinated solvent and the free solvent molecules should be comparatively low, and the spin relaxation time should be short. Successful studies in dimethyl sulphoxide [Th 66], ditnethylformamide [Fr 67a, Fr 67b, Ma 67] and methanol [A1 69b] have been reported. Jackson et al. [Ja 60] have developed a method that can also be used in cases where the proton resonance signals of the coordinated solvent molecules and the free solvent are so close to one another that they do not separate [Ch 68, Al 69a]. 

Contact ion pairs, solvated ion pairs, free ions, and ionic associates can often be experimentally distinguished from each other with UV, IR, Raman, or nuclear magnetic resonance spectroscopy. At room temperature, a tetrahydrofuran solution of sodium fluorenyl... 

---