Ion association of alkaline and alkaline-earth metal perchlorates in acetonitrile

Abstract In this contribution results of a joint investigation by dielectric and infrared spectroscopy into the ion association of LiClO 4 , NaClO 4 , Mg(ClO 4 ) 2 and Ca(ClO 4 ) 2 in acetonitrile solutions at 25 °C are presented. All electrolytes exhibit multi-step ion association. Whereas the alkali salts only form solvent-shared (SIP) and contact ion pairs (CIP), a significant amount of neutral triple ions M (ClO 4 ) 2 ( T 0 ) is additionally observed for the earth–alkali salts. For Ca(ClO 4 ) 2 there are also indications for the formation of [Ca 2 ClO 4 ] 3+ triples ( T + ). Also discussed are effective solvation numbers derived from the acetonitrile relaxation.