Simulation of deep eutectic solvents: Progress to promises

Abstract

Deep eutectic solvents (DESs) are binary or ternary mixtures of compounds that possess significant melting point depressions relative to the pure isolated components. The discovery of DESs has been a major breakthrough with multiple fields benefitting from their low cost and tunable physiochemical properties. However, tailoring DESs for specific applications through their practically unlimited synthetic combinations can be as much a hindrance as a benefit given the expense and time-required to perform large-scale experimental measurements. This emphasizes the need for fast computational tools capable of making accurate predictions of DES physiochemical properties exclusively from molecular structure. Yet, these systems are not trivial to model or simulate at the atomic level given their exceedingly nonideal behaviors, asymmetry of components, and the complexity of their molecular electrostatic interactions. Despite the challenge, computational reports featuring quantum mechanical (QM) methods have provided significant understanding into the relationship between the melting point depression and the unique and complex hydrogen bond network present in DESs. Classical molecular dynamics (MD) methods have examined bulk-phase solvent organization in conjunction with thermodynamic and transport properties. Machine learning (ML) algorithms have shown great potential as structure-property prediction tools. Overall, this review highlights computational accomplishments that have meaningfully advanced our understanding of DESs and strives to give the reader a sense of the overall strengths and drawbacks of the methodologies employed while hinting at promises of advances to come.

Solubilities and Transport Properties of CO2, Oxalic Acid, and Formic Acid in Mixed Solvents Composed of Deep Eutectic Solvents, Methanol, and Propylene Carbonate

“…Deep Eutectic Solvents (DES) are an emerging class of solvents sharing similar properties and advantages with ILs. − Many DES, e.g., choline-based, can be easily prepared from mixing naturally occurring substances and, thus, are cheaper to produce than most ILs. , Compared to ILs, the use of DES in electrochemical processes is not as widely investigated. High viscosities can be a limiting factor toward application of pure DES as electrolytes for the electrochemical reduction of CO 2 .…”

Structure of Deep Eutectic Solvents (DESs): What We Know, What We Want to Know, and Why We Need to Know It

“…Investigations of DES structure through computational modeling can provide insight into structural features that may not be experimentally measurable or provide information on a greater diversity of DES compositions . However, DESs are complex and present challenges to computational modeling …”

“…17 However, DESs are complex and present challenges to computational modeling. 22 Bulk DES Structure. The structure of DESs in the bulk can be tuned by adjusting the molecular composition of the DES components.…”

Comparison between Ab Initio Molecular Dynamics and OPLS-Based Force Fields for Ionic Liquid Solvent Organization

“… − Delocalization of charge over several atoms and asymmetry in either the size or shape of the cation or anion are essential in the construction of these materials. The physical and chemical properties of ILs are fundamentally related to their solvent structure. , Due to their extensive potential to alter physical and chemical behavior through functionalization, considerable effort has been put forth by the IL community to better understand the nature of these intermolecular interactions. − …”