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 5to 45°C. New bands due to solvent molecules in the primary solvation shell ofthe lithium ions were detected in the region of the CN stretching mode of thenitriles and of the CO stretching mode of propylene carbonate. The band structureswere studied in detail by deconvolution with band-fitting procedures and meancation solvation numbers were deduced from the band area of the bulk solvent.For the systems acetonitrile—lithium perchlorate, benzonitrile—lithiumperchlorate, and benzonitrile—lithium thiocyanate, solvation numbers of “free” and“bound” lithium ions were calculated with the help of the degree of associationobtained from suitable anion vibrations.