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) symmetry. Normal coordinate analyses were performed with the BALGA program. Experimental infrared spectra of EMIM were obtained by increasing temperature (between room temperature and 150^oC) 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.

Keywords

• 1-Ethyl-3-methylimidazolium,IR spectra,DFT,HOMA

References

1. [1] Rogers RD, Seddon, KR, Eds., Ionic Liquids IIIA: Fundamentals, Progress, Challenges, and Opportunities - Properties and Structure; Ionic Liquids IIIB: Fundamentals, Progress, Challenges, and Opportunities - Transformations and Processes, American Chemical Society, Washington, DC, 2005.
2. [2] Rogers RD, Seddon KR,Volkov S, Eds., Green Industrial Applications of Ionic Liquids, Kluwer, Dordrecht, 2002.
3. [3] Leal JP, Esperança JMSS, Minas da Piedade ME, Canongia Lopes JN, Rebelo LPN, Seddon KR. The Nature of Ionic Liquids in the Gas Phase. J Phys Chem A 2007; 111: 6176-6182.
4. [4] Earle MJ, Esperança JMSS, Gilea MA, Lopes JNC, Rebelo LPN, Magee JW, Seddon KR, Widegren JA. The distillation and Volatility of Ionic Liquids. Nature 2006; 439: 831-834.
5. [5] Paulechka YU, Zaitsau DH, Kabo GJ, Strechan AA. Vapor Pressure and Thermal Stability of Ionic Liquid 1-Butyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)amide. Thermochim Acta 2005; 439: 158-160.
6. [6] A.-Sada AK, Elaiwi AE, Greenway AM, Seddon KR. Evidence for the Clustering of Substituted Imidazolium Salts via Hydrogen Bonding under the Conditions of Fast Atom Bombardment Mass Spectrometry. Eur J Mass Spectrom 1997; 3: 245-247.
7. [7] Alfassi ZB, Huie RE, Milman BL, Neta P. Electrospray Ionization Mass Spectrometry of Ionic Liquids and Determination of their Solubility in Water. Anal Bioanal Chem 2003; 377: 159-164.
8. [8] Turner EA, Pye CC, Singer RD. Use of ab initio calculation towards the rational design of room temperature ionic liquids. J Phys Chem A 2003; 107: 2277-2288.

9. [9] Katsyuba SA, Zvereva EE, Vidiš A, Dyson P J. Application of density functional theory and vibrational spectroscopy toward the rational design of ionic liquids. J Phys Chem A 2007; 111: 352-370.
10. [10] Katsyuba SA, Dyson PJ, Vandyukova EE, Chernova AV, Vidis A. Molecular Structure, Vibrational Spectra, and Hydrogen Bonding of the Ionic Liquid 1‐Ethyl‐3‐methyl‐1H‐imidazolium Tetrafluoroborate. Helvetica Chem Acta 2004; 87: 2556-2565.
11. [11] Elaiwi A, Hitchcock P B, Seddon KR, Srinivasan N, Tan Y-M, Welton T, Zora, JA. Hydrogen bonding in imidazolium salts and its implications for ambient-temperature halogenoaluminate(III) ionic liquids. J Chem Soc Dalton Trans 1995; 21: 3467-3472.
12. [12] Fuller J, Carlin RT, De Long H C, Haworth D. Structure of 1-ethyl-3-methylimidazolium hexafluorophosphate: model for room temperature molten salts. J Chem Soc Chem Commun 1994; 3: 299-300.
13. [13] Pernak J, Sobaszkiewicz K, Mirska I. Anti-microbial activities of ionic liquids. Green Chem 2003; 5: 52-56.
14. [14] Scammels PJ, Scott JL, Singer RD. Ionic liquids: the neglected issues. Aust J Chem 2005; 58: 155-169.
15. [15] Gathergood N, Scammells PJ. Design and Preparation of Room-Temperature Ionic Liquids Containing Biodegradable Side Chains. Aust J Chem 2002; 55: 557-560.
16. [16] Kruszewski J, Krygowski TM. Definition of aromaticity basing on the harmonic oscillator model. Tet Lett 1972; 13: 3839-3942.
17. [17] Krygowski TM. Crystallographic studies of inter- and intramolecular interactions reflected in aromatic character of .pi.-electron systems. J Chem Inform. Comp. Sci., 1993, 33, 70-78.
18. [18] Krygowski TM, Cyranski M. Separation of the energetic and geometric contributions to the aromaticity of π-electron carbocyclics. Tetrahedron 1996; 52: 1713-1722.
19. [19] Morrison CA, Smart BA, Rankin DWH, Robertson HE, Pfeffer M, Bodenmüller W, Ruber R, Macht B, Ruoff A, Typke V. Molecular Structure of 1,3,5-Triazine in Gas, Solution, and Crystal Phases and by ab Initio Calculations. J Phys Chem A 1997; 101: 10029-10038.
20. [20] Kuş N, Breda S, Reva ID, Tasal E, Ogretir C, Fausto R. FTIR spectroscopic and theoretical study of the photochemistry of matrix-isolated coumarin. Photochem Photobiol 2007; 83: 1237-1253.