Transfer Gibbs energies for ClO3–, BrO3–, IO3–, ClO4– and IO4– anions for water–methanol and water–propan-2-ol mixtures: some quantum-chemical aspects of ionic solvation

Abstract

The transfer Gibbs energies, Δ_trsG^o, of KClO₃, KBrO₃, KIO₃, KClO₄, KIO₄ and the corresponding caesium salts have been obtained through gravimetric measurements of the solubility in aqueous mixtures with methanol (MeOH) and propan-2-ol (PrⁱOH) at 298.2 K. In addition, the solubility of Ph₄P(pic)(pic = picrate anion) as well as K(pic) and KBPh₄ and the corresponding caesium salts are reported in these mixtures at 298.2 K. Single-ion values of Δ_trsG^o have been calculated using the tetraphenylphosphonium tetraphenylborate (TPTB) assumption. The semiempirical quantum-chemical AM1 method was used for calculations of interaction energy of BPh₄^– and Ph₄P⁺ with a series of five solvent molecules and energy demands associated with a deformation of these ions. Trends observed for Δ_trsG^o are discussed in terms of specific ion–solvent interactions and the structural effect of solvent mixtures.