ION SOLVATION ENERGIES - LIMITS OF THE BORN EQUATION APPLICABILITY

Potentials of redox couples formed by cobalt dicarbollide in the charg e states 1-, 2-, and 3- were determined in various aprotic solvents. C omparison of these data with the results we obtained earlier and the l iterature data allow us to conclude that for the solvents, which have no tendency to particularly strong specific interactions (hydrogen bon ds, a strong donor-acceptor interaction), the Born equation for the io n solvation energies is well fulfilled for compact ions if the electri c induction at their surface is lower than about 15 V/nm. This limit d ecreases for ions with open structure providing a partial penetration of a solvent molecule into the ion inner coordination sphere. For smal l and/or multicharge ions with a stronger electric field, the short-ra nge interactions play an important role.