Anion Radical Solvatation Enthalpies as a Function of Cation Size

Article abstract of DOI:10.1021/j100455a010

Calorimetric methods have been utilized to measure the enthalpies of reaction of solvated anthracene anion radical ion pairs with water.These enthalpies were then used in a thermochemical cycle to obtain the heats of solvation of the separated ions in the gas phase (ΔH^o for AN^-._g + M⁺_g --> (AN^-.,M⁺)_solv).These enthalpies were found to be more exothermic when dimethoxyethane (DME) rather than tetrahydrofurane (THF) served as the solvent.However, for both of these solvents the heats of solvation are more exothermic for the smaller cations (increasing exothermicity Cs⁺+++).In THF this enthalpy varies by more than 50 kcal/mol with the size of the cation.The results are explained in terms of ion solvation and ion association, and these results are compared to a previous study where the anion size was varied.