Molecular dynamics simulation studies of 1,3-dimethyl imidazolium nitrate ionic liquid with water

by Selleckchem | Mar 24 2023

The fundamental understanding of intermolecular interactions of ionic liquids (ILs) with water is essential in predicting IL-water thermodynamic properties. In this study, intermolecular or noncovalent interactions were studied for 1,3-dimethyl imidazolium [DMIM]+ cation and nitrate [NO3]- anion with water, employing quantum mechanics and molecular dynamics simulations. Molecular dynamics simulations were performed using a revised multipolar polarizable force field. The effect of water on ionic liquids was evaluated in terms of thermodynamic and dynamic properties. Thermodynamic properties included liquid densities ρ, excess molar volumes ΔVE, and liquid structures gr. Dynamic properties included self-diffusion coefficients D of mixture constituents as a function of water concentration. The density of ionic liquid-water mixtures monotonically decrease with increasing concentration of water. A negative excess volume was obtained for low and high water concentrations, demonstrating strong intermolecular interactions of water with ionic liquid components. Liquid structures of ionic liquid-water mixtures revealed a tendency for anions to interact with cations at shorter intermolecular distances when the water concentration is increased. Diffusion rates were found to increase for all mixture components with increase in the fraction of water. A significant change in the diffusion rate was found at ∼0.3 weight fraction of water. However, the water self-diffusion coefficient was dominant at all concentrations. The ratio of water/anion and anion/cation self-diffusion coefficients was found to decrease linearly with increasing concentration of water molecules.

Comments：

In this study, the researchers investigated the interactions between 1,3-dimethyl imidazolium [DMIM]+ cation and nitrate [NO3]- anion with water using quantum mechanics and molecular dynamics simulations. The researchers used a revised multipolar polarizable force field to perform the molecular dynamics simulations.

The thermodynamic properties of the ionic liquid-water mixtures were studied, including liquid densities, excess molar volumes, and liquid structures. The results showed that the density of the ionic liquid-water mixtures decreased monotonically with increasing concentration of water. The excess molar volumes were negative for low and high water concentrations, indicating strong intermolecular interactions between water and the ionic liquid components. The liquid structures of the mixtures revealed a tendency for the anions to interact with cations at shorter intermolecular distances as the water concentration increased.

The researchers also studied the dynamic properties of the mixtures, including self-diffusion coefficients of the mixture constituents as a function of water concentration. The diffusion rates of all mixture components increased with increasing fraction of water, with a significant change observed at around 0.3 weight fraction of water. However, the water self-diffusion coefficient was dominant at all concentrations. The ratio of water/anion and anion/cation self-diffusion coefficients decreased linearly with increasing concentration of water molecules.

Overall, the study provides fundamental insights into the intermolecular interactions between ionic liquids and water, which are important for predicting the thermodynamic and dynamic properties of ionic liquid-water mixtures.