Using spectroscopic data on imidazolium cation conformations to test a molecular force field for ionic liquids

A molecular force field for the computer simulation of ionic liquids is evaluated a posteriori by confrontation against Raman spectroscopic data, published after the force field had been formulated. Specifically, the terms in the force field describing the conformational aspects of dialkylimidazolium cations, which were specifically developed for these compounds using high level ab initio calculations, are those affecting the distribution of conformers in simulated ionic liquids. Those distributions are compared with analyses of the liquid-phase Raman spectra, and the features of a series of dihedral torsions along the alkyl side chains in 1-alkyl-3-methylimidazolium cations in several ionic liquids are discussed.