Cation Functionalization Alters Cohesion, Not Interaction Type, in Ionic Liquids: Evidence from Infinite Dilution...

Area of Science:

• Physical Chemistry
• Materials Science
• Chemical Engineering

Background:

• Ionic liquids (ILs) are tunable solvents with applications in various chemical processes.
• Understanding solute-solvent interactions in ILs is crucial for designing efficient chemical systems.
• Cation structure significantly influences the properties and solvation behavior of ILs.

Purpose of the Study:

• To investigate the effect of cation functionalization on solute-solvent interactions in ionic liquids.
• To quantify the impact of introducing an oxygen atom into the cation ring on solvation thermodynamics.
• To explore how cation modification influences the affinity of ILs for different types of solutes.

Main Methods:

• Experimental determination of infinite dilution activity coefficients (IDACs) for 34 molecular solutes in two ILs using gas-liquid chromatography.
• Measurements conducted over a temperature range of 308.15 K to 358.15 K.
• Analysis supported by linear solvation energy relationship, regular-solution treatment, and COSMO-RS calculations.

Main Results:

• Insertion of an oxygen atom into the cation ring systematically increases IDACs, reducing solvent affinity.
• This effect is more pronounced for nonpolar solutes than for polar compounds.
• Cation functionalization primarily increases the thermodynamic cost of solvation without changing the fundamental interaction hierarchy.

Conclusions:

• Cation functionalization is a viable strategy for tuning solvation thermodynamics in ILs.
• The study demonstrates that modifying cation structure can control the balance of liquid-state interactions.
• Results provide insights for rational design of ILs with tailored solvent properties.