Cluster-Continuum Model as a Sanity Check of Sodium Ions' Gibbs Free Energies of Transfer

Abstract

An approach to estimate the uncertainty of the calculated through the monomer cycle cluster-continuum model Gibbs free energy of transfer has been developed and suggested to be used as a quantitative measure of the reliability of the predictions. A set of experimental Na+free energies of transfer from water to 18 solvents (Î"Gtr(Na+, W → S)) has been assessed. For all solvents, we find Na+(S)nclusters to be thermodynamically unstable if n > 5. For 1,2-dichloroethane (1,2-DCIE), we have resolved considerable (ca. 10 kcal mol-1) discrepancies between available experimental ΔGtr(Na+, W → S). For 1,1-DCIE, we reject the only available experimental value and recommend our own estimate instead. We strongly propose experimental revisiting of ΔGtr(Na+, W → S) for ethylene glycol and hexamethylphosphoramide. The statistical analysis performed on a set of predicted and recommended experimental ΔGtr(Na+, W → S) values, in this work, results in the mean unsigned and signed deviations of 3.4 and-1.3 kcal mol-1, respectively. The squared Pearson correlation coefficient of 0.91 encourages the extension of the utilized theoretical approach to other available experimental data on ion solvation.