Excess chemical potential of thiophene in the [C4MIM] [BF4, Cl, Br, CH3COO] ILs using Polarizable Forcefields

Thiophene and other aromatic sulfur compounds are some of the hardest pollutants to remove from fuels [1] and a significant cause of air pollution from vehicle emissions, in the form of sulfur oxides. [2,3]. Ionic liquids (IL) are a potential group of solvents with a broad range of interactions with polar and non-polar chemicals. They have distinctive physicochemical characteristics such low vapor pressure and are used as solvents in a number of chemical extraction processes [6,4,5].

Commonly used classical non-polarizable atomistic force fields (FF) are able to reproduce the structural, solvation, and transport properties of ionic liquids (IL) with reasonable agreement with experimental values, in certain cases, by scaling their fixed atomic charges [7,8]. Other calculated properties in condensed phases, however, such as hydrogen-bond length, coordination numbers, viscosities, diffusion coefficients, and dielectric constant, differ from their corresponding experimental values [9].

In an effort to further enhance these traditional non-polarizable forcefields, drude oscillators have been used to incorporate polarization effects. As a result, numerous researchers have created polarizable FF for ILs [7,10,11] that more accurately reproduces both thermodynamic and transport properties.

Regrettably, there are currently very few molecular simulations that use polarizable forcefields to determine the excess chemical potential of thiophene within ILs. Therefore, in this work, the solvation free energies (excess chemical potentials) for thiophene within the ILs [C4mim][Cl], [C4mim][Br], [C4mim][BF4], and [C4mim][CH3COO] were estimated using replica exchange and the PER T module within the CHARMM program [12,13,14].

References:

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