Infrared (attenuated total reflection) study of propylene carbonate solutions containing lithium and sodium perchlorate

Attenuated total reflection infrared spectroscopy was used to examine the concentration dependent solvation of LiClO4 and NaClO4 electrolytes in propylene carbonate (PC). Factor analysis and curve fitting techniques were performed on the measured spectra and the results compared with ab initio computations to provide evidence for ion–solvent solution geometries. Factor analysis of the measured data allowed the identification of the spectrum of ion-associated PC that is uniquely different from the self-associated PC spectrum. The results indicate Li+ and ClO4− ions are contact ion-paired even at relatively low electrolyte concentrations whereas Na+ and ClO4− ions are not, up to ∼2 mol dm−3.