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

The transfer Gibbs energies, Delta(trs) G(n), of KClO3, KBrO3, KlO(4), KClO4, KlO(4) and the corresponding caesium salts have been obtained through gravimetric measurements of the solubility in aqueous mixtures with methanol (MeOH) and propan-2-ol ((PrOH)-O-i) at 298.2 K. In addition, the solubility of Ph(4)P(pic) (pic = picrate anion) as well as K(pic) and KBPh(4) and the corresponding caesium salts are reported in these mixtures at 298.2 K. Single-ion values of Delta(trs) G(0) have been calculated using the tetraphenylphosphonium tetraphenylborate (TPTB) assumption. The semiempirical quantum-chemical AM1 method was used for calculations of interaction energy of BPh(4)(-) and Ph(4)P(+) with a series of five solvent molecules and energy demands associated with a deformation of these ions. Trends observed for Delta(trs) G(0) are discussed in terms of specific ion-solvent interactions and the structural effect of solvent mixtures.