Ion sites in deuterated dimethylsulfoxide solutions of NaNO3 and cryptand complexed NaNO3 by digital infrared spectroscopy

Infrared spectra in digitized form were measured for NaNO₃ and [Na·C221]⁺NO₃^– solutions in DMSO-d₆ between 1150 and 1500 cm^–1 using a technique and instrumentation that obtains each point of the average absorbance spectrum at the same (reduced) noise level. Similar spectra were also obtained for the solvent and the Na⁺ complexed cryptand C221 and used to remove the contribution of these entities from the above spectra. By taking appropriate differences of spectra, it was possible to reveal both bands of the contact ion pair in the NaNO₃/DMSO-d₆ solution-removing one from under the strong band of the D_3h site—and to show the presence of three ion sites in this solution. The third site is tentatively identified as a close ion pair. Two ion sites are also identified in the [Na·C221]⁺NO₃^–/DMSO-d₆ solution.Paper X in the series, Studies of Solution Character, by Molecular Spectroscopy.