| Abstract: | The density functional theory (DFT) has been employed to investigate the electronic structures of EMIM ( 1-ethyl-3-methylimidazolium ), CuCl2-, Cu2Cl3- and EMIM -CuCl2-, EMIM -Cu2Cl3- pairs.Full optimization and frequency analyses of EMIM , CuCl2-, Cu2Cl3-, eight initial EMIM -CuCl2-, and six initial EMIM -Cu2Cl3- geometries have been carried out using Gaussian-94 software-package at 6-31 G (d,p) basis set level for hydrogen, carbon, nitrogen, chlorine atoms and the Hay-Wadt effective core potential for copper atoms. The electronic structures of the lowest energy of EMIM -CuCl2-, EMIM -Cu2Cl3-pairs, single EMIM , CuCl2-, and Cu2Cl3- have been comparatively studied. The calculated results showed that the optimized EMIM -CuCl2- pair conformer of the lowest energy was five ring moiety parallel to CuCl2- plane with a distance of around 3.5A, while EMIM -Cu2Cl3- pair conformer of the lowest energy was five ring moiety of EMIM perpendicular to Cu2Cl3- plane with a distance of around 3.0 A between terminal chlorine atoms and 5-ring plane of EMIM~. The cohesion between cation and anion is electrostatic interaction and C-H-Cl hydrogen bonds are reinforced by charge assistance. The frequency analyses suggested that all stationary points are minimum points because of absence of imaginary frequency. The low energy of interaction caused by bulky asymmetry of EMIM , and charge dispersion of cation and anion give rise to low melting point of ionic liquids EMIM -CuCl2-, and EMIM -Cu2Cl3-. The interaction energy caused by the distance between cations and anions was investigated by single point energy scan. |
