Anion-based regulating mechanism of structural and diffusive property of ionic liquids

Understanding the regulating mechanism of diffusive properties of ionic liquids (ILs) is vital for their practical chemical engineering applications. Herein, we investigate the regulating mechanism of three properties, the structural, thermodynamical, and diffusive properties, of imidazole ILs with 18 kinds of anion via molecular dynamics simulations combined with theoretical analysis. It shows that the radial distribution function and coordinate number for these 18 ILs are similar to each other. However, the vibrational spectrum and diffusive property change greatly with the anion structure, in which the self-diffusive coefficient (SDC) even changes by an order of magnitude. Furthermore, free energy and entropy have an exponential relationship with SDC, while other structural properties or cation-anion correlations cannot be directly related to SDC. These quantitative relationships suggest that entropy or free energy can serve as the key indicators in designing functional ILs for high-performance applications in the chemical engineering field.

Automated summary

In this study, the regulating mechanism of structural, thermodynamical, and diffusive properties of 18 imidazole ionic liquids (ILs) with different anions was investigated using molecular dynamics simulations and theoretical analysis. It was found that the radial distribution function and coordinate number of these ILs were similar, while the vibrational spectrum and diffusive property varied greatly with the anion structure, resulting in a significant change in the self-diffusive coefficient (SDC). Moreover, the SDC was found to have an exponential relationship with free energy and entropy, suggesting that these can be key indicators in designing high-performance ILs for practical chemical engineering applications.