|Name||Mr. Xiang Zhong|
A CUSTOM OPLS-AA FORCE FIELD FOR DICATIONIC IMIDAZOLIUM-BASED IONIC LIQUID SIMULATIONS
Xiang Zhong, Brian Doherty, and Orlando Acevedo*
Department of Chemistry, University of Miami, Coral Gables, FL 33146
Ionic liquids are a remarkable class of solvents composed exclusively of ions, characteristically at room temperature. Recently, imidazolium-based dicationic ionic liquids (DILs) have gained promising attention as a solvent medium for organic reactions, such as Claisen rearrangements, due to a broader variability in physical properties, e.g., increased thermal stability compared to 1-alkyl-3-methylimidazolium [RMIM]. This study focuses on simulations of 3,3’-(1, N-diyl)bis[1-methyl], where N=5-pentane, 6-hexane, 8-octane, 9-nonane, 10-decane, and 12-dodecane, in conjunction with the bis(trifluoromethylsulfonyl)imide [TFSI] anion. The unique sets of DIL force field parameters were developed by adapting our OPLS-2009IL force field (Sambasivarao, S. V.; Acevedo, O., J. Chem. Theory Comput. 2009, 5, 1038-1050), which was originally created for [RMIM]. Molecular dynamics simulations were performed using GROMACS for the combination of each C5-[MIM]2, C6-[MIM]2, C8-[MIM]2, C9-[MIM]2, C10-[MIM]2, and C12-[MIM]2 cation with the [TFSI] anion. Predictions from OPLS-2009IL DIL force field are presented for relevant solvent data that includes: densities, heats of vaporization, diffusion coefficients, and heat capacities. It has been shown for [RMIM]-based ionic liquid simulations that scaling charges improves thermodynamic properties, such as heat of vaporization, and transport properties. A scaling of ±0.8 e was also tested for the DILs.