Theoretical and Experimental Infrared Spectrum Analysis of 1-Ethyl-3-Methylimidazolium Cation

Abstract

In this study, molecular structure of 1-ethyl-3-methylimidazolium cation (EMIM +) was undertaken at the DFT(B3LYP)/6-311++G(2d,2p) level of approximation using the GAUSSIAN 09 suit of programs. EMIM has two conformers (EMIM-1 and EMIM-2) with minimum energies. EMIM-1 and EMIM-2 were found C1 (double degenerated by-symmetry form) and Cs symmetries, respectively. Normal coordinate analyses were performed with the BALGA program. Experimental infrared spectra of EMIM were obtained by increasing temperature (between room temperature and 150 o C) and compared with calculations. Assignment of the spectra and normal coordinate analyses to characterize the vibrations in EMIM conformers were undertaken. p-electron delocalization through the aromaticity index Harmonic Oscillator Measure of Aromaticity (HOMA) of EMIM calculated using Kruszewski and Krygowski definations.