NUCLEAR MAGNETIC RESONANCE STUDY OF CONFIGURATIONS AND INTERIONIC SEPARATIONS IN R4N+MXN3- ION PAIRS

A systematic nmr study was made of line widths and chemical shifts for ion pairs in solution, consisting of tetraethylammonium ions and various complex paramagnetic anions of iron(III) and chromium(III). Anions of identical charge (3-) but of varying size were employed in the study. Solutions in solvent mixtures of D2O and dimethyl-d6 sulfoxide were investigated over the temperature range 6-95° Results of the study indicate that the experimental data are best fit by a model in which there is restricted tumbling of the counterions within the ion pairs. Calculated interionic separations indicate that “contact” ion pairs are formed in dimethyl-d6 sulfoxide, and “solvent-separated” ion pairs are formed in D2O. Only minor changes in configuration are observed over the temperature range studied. © 1969, American Chemical Society. All rights reserved.