Vol. 7, Issue 2, Part A (2025)

Theoretical and computational analysis of binary mixtures composed of ionic liquids (ILs) and cyclic ethers offers critical insights into their non-ideal thermodynamic behavior and complex molecular interactions. These hybrid liquid systems have emerged as versatile and tunable media with potential applications across green chemistry, separation science, catalysis, electrochemical energy systems, and advanced solvent engineering, owing to their exceptional solvation properties and structural flexibility.
In this study, we employ a multi-theoretical framework combining density functional theory (DFT), molecular dynamics (MD) simulations, and thermodynamic excess function modeling to investigate the nature, extent, and energetic profiles of intermolecular interactions within IL-ether mixtures. Representative imidazolium-based ILs [C₄mim] [Cl], [Bmim][BF₄], and [Bmim][PF₆] are paired with cyclic ethers such as tetrahydrofuran (THF) and 1,4-dioxane to explore the influence of anion structure, ether polarity, and mole fraction on molecular behavior.
DFT calculations reveal the predominance of hydrogen bonding between ether oxygen atoms and the acidic C2-H sites on the imidazolium ring, as well as ion-dipole interactions involving both the cation and anion components. MD simulations confirm these findings through radial distribution function (RDF) analyses, indicating short-range molecular ordering and strong directional associations. Thermodynamic modeling shows positive excess enthalpy, negative excess molar volume, and composition-dependent Gibbs free energy, highlighting the disruption and reorganization of IL-IL and ether-ether networks upon mixing.
The results underscore the role of specific structural features such as anion basicity, hydrogen bonding capacity, and ring strain in governing interaction strength and macroscopic behavior. These theoretical insights offer a predictive foundation for the rational design of IL-ether mixtures tailored to meet the demands of specific applications, including fuel formulation, green solvent systems, and targeted extraction technologies.
This study not only advances the understanding of molecular interactions in IL-based binary mixtures but also supports the broader development of next-generation functional fluids through integrative computational approaches.