|Name||Mr. Brian Doherty|
|Organization||University of Miami|
IONIC LIQUID OPLS-AA FORCE FIELD PARAMETERS FOR MOLECULAR DYNAMICS SIMULATIONS
Brian Doherty, Xiang Zhong, Symon Gathiaka, Bin Li, and Orlando Acevedo
Department of Chemistry, University of Miami, Coral Gables, Florida 33146
Ionic liquids (IL) have been proposed as alternatives to volatile organic solvents. These “designer” solvents are usually composed of a low symmetry organic cation and a weakly coordinating inorganic or organic anion. The cation of interest is 1-alkyl-3-methylimidazolium [RMIM] (R = E for ethyl, B for butyl, etc.), which is popular for its hydrogen bonding ability that can potentially enhance rates and stabilize substrates in multiple organic reactions. Ionic liquid parameters have been developed and tested using our non-polarizable OPLS-2009IL force field (Sambasivarao, S. V.; Acevedo, O., J. Chem. Theory Comput. 2009, 5, 1038-1050) as the foundation. Molecular dynamics simulations using GROMACS were carried out for multiple combinations of [RMIM] and anions, i.e., acetate, tetrachloroaluminate, tetrafluoroborate, benzoate, bromide, chloride, dicyanamide, formate, methylsulfate, nitrate, hexafluorophosphate, propionate, thiocyanate, tricyanomethanide, perchlorate, triflate, and bistriflimide. Computed densities, heats of vaporization, viscosities, diffusion coefficients, and other relevant solvent data compared favorably to experiment. A scaled charge model of each IL ion pair was also investigated as a means to mimic polarization and charge transfer effects.