Attenuated total reflection Fourier-transform infrared spectroscopic study of ion–solvent and ion–ion interactions in lithium perchlorate–nitromethane solutions

Abstract

Lithium perchlorate solutions in nitromethane, 0.04–0.18 mol dm^–3, have been investigated using attenuated total reflection Fourier-transform infrared (ATR FTIR) spectroscopy. Despite the relatively poor electron-donating ability of nitromethane, some evidence for lithium ion coordination is seen. Frequency shifts for the symmetric NO₂ stretching fundamental of +7 cm^–1, and for the symmetric CH₃ bending fundamental of +2 cm^–1 are found for nitromethane complexed to the alkali-metal cation. The infrared-active absorption for the ClO^–₄ anion at 1100 cm^–1 shows substantial splitting, an effect due to the extensive ion-pairing of the solute species. The distribution and relative concentrations of the different electrolyte species were found to be concentration dependent.