Demystifying Preferential Solvation Phenomena.

Area of Science:

• Physical Chemistry
• Solution Chemistry
• Thermodynamics

Background:

• Preferential solvation describes how solutes interact differently with components of mixed solvents.
• Accurate assessment is crucial for understanding chemical reactions, protein behavior, and cosolvency phenomena.
• Existing models often lack a universal, molecular-based framework for diverse solvent systems.

Purpose of the Study:

• To derive a rigorous, molecular-based expression for assessing preferential solvation in any binary mixed-solvent system.
• To characterize a universal representation of the preferential solvation function (PS).
• To link the PS function to fundamental structure-making/breaking functions for mechanistic interpretation.

Main Methods:

• Developed formal expressions for inverting the Kirkwood-Buff approach to determine total correlation function integrals.
• Utilized molecular-scale perturbations and thermodynamic responses (solute's standard chemical potential) to define the PS function.
• Linked the universal PS function to fundamental structure-making/breaking functions (Sαβ).

Main Results:

• Established a unique, molecular-based signature for unambiguous assessment of preferential solvation.
• Formulated rigorous assessment for ternary systems, including dissociative and nondissociative species.
• Successfully linked preferential solvation to structure-making/breaking functions, enabling interpretation of cosolvent effects.

Conclusions:

• The derived universal preferential solvation function provides a robust framework for diverse solvent mixtures.
• This approach facilitates understanding of cosolvent effects on protein conformation, reaction kinetics, and cosolvency/co-nonsolvency.
• The molecular-scale insights offer a powerful tool for designing and optimizing chemical processes in mixed solvents.