عنوان مقاله [English]
The geometrical and electronic structures of four imidazolium-based ILs with different alkyl chain length paired with dicyanamide anion were studied and the effect of ether functionalization was also investigated. The geometrical structures and relative stabilities of the ion pairs were discussed. In the most stable geometries, the anion locates above the imidazolium plane and has close contact with the C2–H of cation. The cation-anion interaction energies (Eint) were also calculated for the most stable conformers. The Eint values have no clear trend with alkyl chain lengthening for imidazolium-based ILs, whereas decrease for ether-functionalized ones. It was found that the interaction energies increase with ether functionalization. MEP surfaces were created in order to elucidate the sites of the cations and anions at which they are most likely to interact. The cation-anion interaction in the most stable conformers were investigated by performing the NBO analysis, the partial charges and E(2) were evaluated. Finally, the gas phase enthalpy of formation of the studied ionic liquids has been calculated by G3(MP2) level using atomization energy approach. The effect of the alkyl side chain length upon the enthalpy of formation of the ionic liquids was also studied. The calculated enthalpies of formation were found to decrease in magnitude with increasing alkyl side chain length and the contribution of the CH2 group was also calculated.