Increasing ion pairing and aggregation in supercooled and glassy dilute aqueous electrolyte solution as seen by FTIR spectroscopy of alkali metal thiocyanates

Abstract

FTIR spectra of aqueous solutions of lithium (1 M), sodium (0.04, 0.2, and 1 M), and potassium (1 M) thiocyanate in their glassy states at 83 K, and of 1 M sodium thiocyanate in supercooled solution from 298 to 230 K, are reported from 1950 to 2200 cm -1 . In the CN stretching band region of the glassy solution derivative spectra, up to six discrete bands are observed. The band at ≃2050 cm -1 is assigned to mainly «free» SCN - . Bands at 2071, 2068, and 2067 cm - are assigned contact ion pairs Li + NCS - , Na + NCS - , and K + NCS -