Raman spectroscopic study of lithium and sodium perchlorate association in propylene carbonate-water mixed solvents

Abstract

Raman spectra of 1 M solutions of LiClO4 and NaClO4 in propylene carbonate (PC) with different amounts of water added (H2O/cation mole ratio = 0-55.5) were recorded in the spectral region 880-980 cm-1. Principal component analysis, a statistical method and deconvolution were applied in investigating the association in these solutions. The results indicate the existence of a band at the high-wavenumber side of the v1 band of free perchlorate anion. As established by deconvolution, the position of the band is at 938-940 cm-1. This band is attributed to monodentate contact ion pairs and is present in the solutions of perchlorates in pure PC and with a minimum amount of water added. The presence of monodentate contact ion pairs was established by deconvolution of the Raman spectrum of a 1 M solution of Mg(ClO4)2 in pure PC, but at very low concentration. (C) 2000 John Wiley and Sons, Ltd.