Chemical shift of alkali metals

In order to simplify the determination of free energies of transfer, Covington et deduced a relation between AG and the chemical shifts of ions. It is well known that the chemical shift of alkali metal and halide ions in mixed solvents e.g. 

A useful probe of the immediate chemical environment of solute ions is the NMR chemical shift of alkali metal ions obtained in binary solvent mixtures [111, 126, 295]. These measurements are based on the assumption that the chemical shift of the solute cation is determined in an additive fashion by the solvent molecules comprising the first solvation shell. For example (cf. Fig. 2-11), the iso-solvation point of Na in dimethyl sulfoxide/acetone mixtures occurs at xxO.21 cmol/mol dimethyl sulfoxide, indicating the higher solvating ability of this solvent relative to acetone. As shown schematically in Fig. 2-11, the preferential solvation of Na by dimethyl sulfoxide displaces its chemical shift towards <5dmso and a deviation from the straight line is observed. 

Counterions. 1. Sodium-23 Alkali metal MIR is a sensitive >robe of the immediate chemical environment and mobility of alkali metal ions in aqueous and nonaqueous solvents (7, 8). The chemical shifts of alkali metal nuclei will respond to" electronic changes only in the immediate environment of the cation since alkali metals rarely participate in covalent bonding (7). All alkali metal nuclei have spins greater than 1/2 and hence have quadrupole moments. The interaction of these moments with electric field gradients, produced by asymmetries in the electronic environment, is modulated by translation and rotational diffusive motions in the liquid. It is via this relaxation mechanism that the resonance line width is a sensitive probe of ionic mobility. 

The chemical shifts of alkali metal nuclei are a very direct probe of ionic solutions and related systems (6,7,8,9). Perturbations of the... 

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