Quantum Chemistry Study of the Ionic Liquid 1-ethyl-3-methylimidazolium Tetrafluoroborate

The results of the quantum chemistry study of the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM+BF4-) were reported. The ab initio method and density functional theory (B3LYP method) was used to optimize the stable structure of the gas phase ion pair at the level of 6-311++G** basis set, respectively. An IR spectra for EMIM+BF4- were obtained through the vibrational analysis. The changes of atomic charge assignments have been investigated using the Natural Bond Orbital method. The computational results show that there exist hydrogen bonds and other weak interactions between the cation and the anion. Using counterpoise correction method to estimate the basis set superposition error, the interaction energy between the cation and anion is 346.78 kJ/mol.