Molecular dynamic insight into imidazolium based deep eutectic solvent comprising carboxylic acids (C2 and C3): Experiments and DFT approach

The physical properties including speed of sound (u), densities (ρ), refractive indices (nD) for the binary systems of 1:3 mol ratio of [1-butyl-2,3-dimethylimidazolium chloride to ethylene glycol], [BDMIM]Cl: EG], deep eutectic solvent (DES) and selected carboxylic acids (acetic acid and or propanoic acid) were measured including those of pure DESs at temperatures ranging from (293.15–313.15) K at atmospheric pressure using Anton Paar densitometer and Anton Paar refractometer. The measured data was used to calculate excess molar volumes ($V_m^E$), deviation in isentropic compressibilities (Δ$k_s$), intermolecular free length (L_f), deviation in refractive indices (ΔnD) and isentropic compressibilities (k_s), these thermodynamic properties will be used to examine the types of intermolecular interactions between the prepared systems comprising imidazolium DES and acetic acid or propanoic acid. DFT calculations, natural bond order (NBO) analysis, electron localization function (ELF) and non-covalent interaction (NCI) analysis was done to understand the interactions occurring with DES and DES-carboxylic acid systems. Molecular Dynamics Simulations were also done for 250 ns to study root mean square deviation, root mean square fluctuations and radial distribution function of DES and DES-carboxylic acid systems. Lorentz-Lorenz equation was applied to correlate the volumetric properties and to predict the density and the refractive indices of binary mixtures. The predicted data were in good agreement with the experimental data.