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

FTIR spectra of lithium perchlorate and lithium thiocyanate in acetonitrile, benzonitrile, and propylene carbonate were recorded in the temperature range from 5 to 45 degreesC. New bands due to solvent molecules 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 numbers were deduced from the band area of the bulk solvent. For the systems acetonitrile-lithium perchlorate, benzonitrile-lithium perchlorate, and benzonitrile-lithium thiocyanate, solvation numbers of "free" and "bound" lithium ions were calculated with the help of the degree of association obtained from suitable anion vibrations.