Influence of Hydration on the Structure of Reline Deep Eutectic Solvent: A Molecular Dynamics Study

Abstract

In this article, we have performed an all-atom molecular dynamics simulation study to investigate the influence of water on the molecular level arrangement of reline deep eutectic solvent for different hydration levels ranging from 3.4 to 58.1 wt % of water and complemented the observations of recently measured neutron scattering experimental data. This study is particularly important because water is being introduced as a second hydrogen bond donor/acceptor in reline, wherein the structure is primarily governed by hydrogen bonding and electrostatic interactions. We have analyzed the simulated X-ray scattering structure functions, their partial components, and hydrogen bonding interactions to understand the effects of water on various intermolecular interactions in reline–water mixtures. It is observed that at lower hydration level, reline structure is qualitatively retained. At higher hydration level, most water molecules preferentially solvate chloride anions and ammonium group of choline cations mostly impacting choline–choline, choline–chloride, and chloride–chloride interactions. The present study reveals that at and above 41 wt % of water, the molecular arrangement of reline drastically changes and set to transition from reline to an aqueous solution of reline components with further increase in the hydration level. Hydrogen bond analysis reveals the presence of strong chloride–water H-bonding interaction, which gradually replaces choline–chloride and urea–chloride hydrogen bondings as the hydration level in the mixture increases.

Structural, Thermodynamic, and Transport Properties of Aqueous Reline and Ethaline Solutions from Molecular Dynamics Simulations

“…41 Our results further indicate that water preferentially solvates the Cl – anion over cation. 41 This can be seen also by the HB networks between water molecules and the species of DESs, which are presented in Figure S10 of the Supporting Information. It is found that EG makes approximately 0.7 HBs per EG with the anions in the absence of water, whereas the addition of 80% of water greatly decreases this to 0.04 HBs per EG molecule.…”

“…27 Recently, the influence of the hydration of different DESs was investigated using MD simulations, particularly focusing on static properties including densities, RDFs, spatial distributions, and hydrogen bonding. 39−41 Baz et al 42 performed MD simulations to compute static and dynamic properties of glyceline–water mixtures at various temperatures. The simulations were additionally supported by equation-of-state modeling.…”

Influence of water content and applied potential on the electrodeposition of Ni coatings from deep eutectic solvents

“…Recently it has been shown that H 2 O content significantly influences the interactions of DES constituents (water, choline, urea, chloride and nickel) [41,44,45]. Therefore, it is known that the increase of water content from 0.1 wt% to 2.1 wt% (or to 0.25 wt% in blank electrolyte) changes the interactions between water and DES components by possibly increasing the electrolyte integrity, which occurs by strengthening the Ch þ -Cl e interactions [42]. This could cause the shift of Ni 2þ reduction to more negative potentials upon presence of small amounts of water (up to $2-3 wt%).…”

Band-Gap Energies of Choline Chloride and Triphenylmethylphosphoniumbromide-Based Systems

“…Only System 2 (choline chloride/imidazole) showed an energy value below 5 eV. Among systems containing triphenylmethylphosphonium bromide, System 5 was of interest, showing an indirect band gap of 3.74 eV, similar to other known semiconductors [30][31][32][33]. To date, 3.74 eV is the lowest value of an energy band gap ever reported for such kind of systems.…”