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

In this contribution results of a joint investigation by dielectric and infrared spectroscopy into the ion association of LiClO4, NaClO4, Mg (ClO4)(2) and Ca(ClO4)(2) in acetonitrile solutions at 25 degrees 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(ClO4)(2) (T-0) is additionally observed for the earth-alkali salts. For Ca(ClO4)(2) there are also indications for the formation of [Ca2ClO4](3+) triples (T+). Also discussed are effective solvation numbers derived from the acetonitrile relaxation. (C) 2006 Elsevier B.V All rights reserved.