Development of Imidazolium-Based Parameters for AMOEBA–IL

A new approach for the efficient parametrization of the polarizable ionic liquid potential AMOEBA–IL, and its application to develop parameters for imidazolium– based cations is presented. The new approach relies on the development of parameters for fragments that can be transferred to generate new molecules. The parametrization uses the original AMOEBA–IL parametrization approach, in- cluding the use of Gaussian Electrostatic Model-Distributed Multipoles (GEM-DM) for the permanent multipoles and approximation of the Van der Waals parameters using quantum mechanics energy decomposition analysis (QM-EDA) data. Based on this, functional groups of the selected initial structures are employed as building blocks to develop parameters for new imidazolium-based cations (symmetric or asymmetric) with longer alkyl chains. The parameters obtained with this proposed method were compared with inter-molecular interactions from QM references via energy decomposition analysis using Symmetry Adapted Perturbation Theory (SAPT) and counterpoise corrected total inter-molecular interactions. The validation of the new parametrized cations was carried out by running molecular dynamics simulations on a series of imidazolium-based IL’s with different anions to compare selected thermodynamic and transport properties, including density ρ, enthalpy of vaporization ∆H vap , radial distribution function g(r), and diffusion coefficients D±, with experimental data. Overall, the calculated gas–phase and bulk properties show agreement with the reference data. The new procedure provides a straightforward approach to generate the required AMOEBA–IL parameters for any imidazolium-based cation.