FTIR spectroscopy of ion solvation of LiClO4 and LiSCN in acetonitrile, benzonitrile, and propylene carbonate

Abstract

FTIR spectra of lithium perchlorate and lithium thiocyanate in acetonitrile, benzonitrile, and propylene carbonate were recorded in the temp. range from 5 to 45 °C. New bands due to solvent mols. in the primary solvation shell of the lithium ions were detected in the region of the CN stretching mode of the nitriles and of the CO stretching mode of propylene carbonate. The band structures were studied in detail by deconvolution with band-fitting procedures and mean cation solvation nos. were deduced from the band area of the bulk solvent. For the systems acetonitrile-lithium perchlorate, benzonitrile-lithium perchlorate, and benzonitrile-lithium thiocyanate, solvation nos. of "free" and "bound" lithium ions were calcd. with the help of the degree of assocn. obtained from suitable anion vibrations.