(156d) Modelling Solubility of Metal Complexes in Non-Aqueous Media from First Principle Calculations: Application to Redox Flow Cell

Solubility is a very fundamental equilibrium thermodynamical property and needs to be addressed in non-aqueous Redox Flow Cell because the energy density of a cell is directly related with the solubility of redox active species in non-aqueous medium. At present, there is no such efficient way to predict the solubility of transition metal complexes in non-aqueous media from first principle calculations. During solubility, the transition metal complex and the non-aqueous solvent are in equilibrium with each other. At equilibrium condition, one can predict solubility by modelling the activity coefficient at infinite dilution of the redox active species in the non-aqueous solvent. We have used the first principle COSMO calculation followed by post statistical thermodynamical treatment of self-consistent properties of the solute and solvent molecules for our calculations. The transition metal complex and the non-aqueous medium have been treated as a simple binary mixture using “LANL” activity coefficient model. We used the new activity coefficient model to explain the duel-solute effect already found in the Vanadium redox flow cell containing Vanadium (III) acetylacetonate (V(acac)₃) as redox active species, ionic liquids as supporting electrolytes and Acetonitrile as organic solvent. The present model has been applied to a set of non-aqueous solvents and probable mixtures of them. The solvation mechanism of the metal complexes in those non-aqueous media was obtained from our calculations. We have compared our results with the other experimental and theoretical results wherever they are available to check the accuracy of the new activity coefficient model.