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

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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.