An overview of the performance of the COSMO-RS approach in predicting the activity coefficients of molecular solutes in ionic liquids and derived properties at infinite dilution

Abstract

This paper reports a comprehensive evaluation of the conductor-like screening model for real solvents (COSMO-RS) in predicting infinite dilution activity coefficients (γ^∞) of molecular solutes in ionic liquids (ILs). In particular, comparative analysis of two quantum chemical levels of calculations used in the COSMO part of COSMO-RS, namely, TZVP-COSMO and TZVPD-FINE, is presented and discussed. The final assessment of the model performance is established based on a comparison of its predictions with the experimental data pool consisting of 41 868 data points extracted form 182 references, covering 233 ILs (including salts belonging to 12 different cationic families) and 150 molecular solutes (including a great variety of non-polar, polar and self-associating organic compounds and water) combined with 8554 distinct binary systems. The impact of the chemical family of both IL and molecular solute on the accuracy of the COSMO-RS predictions is analyzed in terms of both quantitative and qualitative measures. Relevant thermodynamic properties derived from γ^∞, namely, infinite dilution partial excess enthalpy of mixing and infinite dilution selectivity are considered and their values obtained from experimental and COSMO-RS predicted γ^∞ data are confronted. Finally, the impact of the molecular conformation of cations/anions/solutes on the quality of predictions is demonstrated based on some representative systems.