Attenuated total reflection fourier-transform infrared spectroscopic study of ion–solvent and ion–ion interactions in alkali-metal perchlorate–acetonitrile solutions

Abstract

A detailed study of the effect of alkali-metal perchlorates, especially LiClO₄ and NaClO₄, on the spectral features of acetonitrile has been made using attenuated total reflection FTIR spectroscopy. The effect of the electrolyte on the C—H stretching and deformation modes together with new information on the CN and C—C stretching modes is analysed in detail. It is shown on the basis of spectra obtained in the deuteriated acetonitrile that the Cl—O symmetrical stretching vibration (ν₁) is IR active when the anion is paired to a cation. Analysis of the perchlorate region of the spectrum provided further information on ion pairing in this system.