Nuclear Magnetic Resonance in Molten Salts. II. Chemical Shifts in Thallium Halide—Alkali Halide Mixtures

Abstract

The resonance frequency of the ²⁰⁵T1 nucleus in molten solutions of the thallous halides with the corresponding alkali metal halides varies linearly with the mole fraction of the added alkali halide. The direction of the chemical shift depends upon the radius of the alkali cation, being upfield for lithium and sodium halides and downfield for the halides of potassium, rubidium, and cesium relative to the pure thallous halide. For a given mole fraction of alkali halide, δ_T1 is a linear function of the alkali cation radius. The results provide information on the nature of the interactions between cations and anions in molten salts. The covalent interaction between T1⁺ and halide ions is decreased by alkali metal ions of small radius and increased by those of large radius.