Anatomy of Microscopic Structure of Ethaline Deep Eutectic Solvent Decoded through Molecular Dynamics Simulations

Area of Science:

• Physical Chemistry
• Computational Chemistry

Background:

• Deep eutectic solvents (DESs) exhibit unique properties influenced by their molecular composition and hydrogen bonding.
• Ethylene glycol (EG) as a hydrogen bond donor in DESs leads to complex structural arrangements due to its intra- and intermolecular hydrogen bonding capabilities.

Purpose of the Study:

• To investigate the microscopic structure and molecular-level ordering of ethaline (choline chloride:EG, 1:2 molar ratio) using atomistic molecular dynamics simulations.
• To assess the efficacy of refined force-field parameters for EG in accurately modeling ethaline DES.

Main Methods:

• Atomistic molecular dynamics simulations were employed to model ethaline DES.
• Simulated X-ray scattering structure functions, radial distribution functions, radial-angular distribution functions, and spatial distribution functions were used for analysis.

Main Results:

• Simulations revealed both short-range and long-range interactions within ethaline.
• Hydrogen bonding interactions between choline cation ([Ch]+), chloride anion ([Cl]-), and EG were extensively observed.
• A competitive hydrogen bonding interaction between [Ch]+ and EG for the [Cl]- anion was identified.

Conclusions:

• The study elucidates the intricate molecular-level structure of ethaline DES.
• Hydrogen bonding plays a critical role in defining the structural morphology and interactions within the DES.
• The findings highlight the complex interplay between the components, particularly the competition for hydrogen bonding.