A quantum-chemistry and molecular-dynamics study of non-covalent interactions between tri-n-butyl phosphate and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Abstract

• A multiscale approach for evaluating interactions between extractant and ionic liquids was proposed. • Good agreements between MD simulations and experimental data on the physical properties of the extractant/ILs mixture. • Different local structures were observed at different extractant concentration. The complicated behavior of extractants in ionic liquids (ILs) has posed great challenges for radionuclides separation and purification. In this regard, a theoretical investigation of combining quantum chemical (QC) calculations and molecular dynamics (MD) simulations was performed to explore the local structures, intermolecular interactions, and dynamic behaviors between the tri- n -butyl phosphate (TBP) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C 4 mimTf 2 N) system. It is demonstrated that the ion pair of C 4 mimTf 2 N rather than the separated ions is more favored either in the gas phase or in solution. Their interaction with TBP is primarily dominated by the electrostatic interaction in most cases, while the dispersion and induction ones are non-negligible. Simultaneously, the intermolecular changes the atom charges of TBP and C 4 mimTf 2 N. Similar local structures have been accessible by both QC and MD calculations. It is revealed that the local structures and intermolecular interactions are strongly dependent on the TBP concentration.