Structure and Thermodynamic Properties of Imidazolium-Based Ionic Liquids with Dicyanamide Anion: A Molecular Dynamics Study

Document Type : Research Article


Department of Chemistry and Center for Research in Climate Change and Global Warming (CRCC), Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, I.R. IRAN


Imidazolium-based Ionic Liquids (ILs) with the dicyanamide anion, [N(CN)2]-, have low melting temperature, high thermal and chemical stabilities, high ionic conductivity and low viscosity making them ideal candidates in the different industrial applications. In this work, the structural and thermodynamic properties of two ILs based on 1-alkyl-3-methylimidazolium cation, [amim]+, (alkyl = methyl and ethyl) and [N(CN)2]-, are studied using molecular dynamics simulations. The non-polarizable all-atom force field was applied to investigate the influence of the effect of changing alkyl side chain from methyl to ethyl and temperature on the behavior of ILs. The quantities such as the radial distribution function, spatial distribution function, the density of IL, molar volume, isobaric thermal expansion coefficient, and enthalpy of vaporization were studied. The density of the [dmim][N(CN)2] is larger than that of the [emim][N(CN)2] at all temperatures because of the relatively higher symmetry and greater packing of [dmim]+ in the liquid state. With increasing alkyl chain length from methyl to ethyl, the electrostatic interactions between ions are weakened and the van der Waals interactions are strengthened, and consequently, the enthalpy of vaporization is decreased.


Main Subjects

[1] Lei Z., Chen B., Koo Y-M., MacFarlane D. R., Introduction: Ionic Liquids, Chem. Rev., 117(10): 6633-6635 (2017). This Article is Part of the Ionic Liquids Special Issue: 6633-7240.
[2] Wasserscheid P. and T. Welton T., (Eds.) Ionic Liquids in Synthesis, 2nd ed., Wiley-VCH: Weinheim, (2008).
[3] Seki S., Kobayashi T., Kobayashi Y., Takei K., Miyashiro H., Hayamizu K., Tsuzuki S., Mitsugi T., Umebayashi Y., Effects of Cation and Anion on Physical Properties of Room-Temperature Ionic Liquids, J. Mol. Liq., 152: 9-13 (2010).
[5] Neves C. M. S. S.,  Kurnia K. A.,  Coutinho J. A. P.,  Marrucho I. M., Lopes J. N. C., Freire M. G., Rebelo L. P. N., Systematic Study of the Thermophysical Properties of Imidazolium-Based Ionic Liquids with Cyano-Functionalized Anions, J. Phys. Chem. B, 35: 10271-10283 (2013).
[6] Weber H., Kirchner B., Complex Structural and Dynamical Interplay of Cyano-Based Ionic Liquids, J. Phys. Chem. B, 120: 2471−2483 (2016).
[7] Kiefer J., Noack K., Penna T. C., Ribeiro M. C. C., Weber H., Kirchner B., Vibrational Signatures of Anionic Cyano Groups in Imidazolium Ionic Liquids, Vib. Spectrosc., 91: 141-146 (2017).
[8] Koller T.M., Ramos J., Schulz P.S., Economou I.G., Rausch M.H., Fröba A.P., Thermophysical Properties of Homologous Tetracyanoborate-Based Ionic Liquids Using Experiments and Molecular Dynamics Simulations, J. Phys. Chem. B, 121:4145-4157 (2017).
[9] Lopes J.N.C., Deschamps J., Pádua A. A. H., Modeling Ionic Liquids Using a Systematic All-Atom Force Field, J. Phys. Chem. B, 108: 2038-2047 (2004).
[10] Lopes J. N. C., Deschamps J., Padua A. A. H., Molecular Force Field for Ionic Liquid III: Imidazolium, Pyridinium, and Phosphonium Cation; Chloride, Bromide, and Dicynamide Anion, J. Phys. Chem. B,110: 19586-19592 (2006).
[11] Nośe S., A Unified Formulation of the Constant Temperature Molecular Dynamics Methods, J. Chem. Phys., 81: 511-519 (1984).
[12] Smith W., Forester T. R., Todorov I.T., “The DL_POLY Molecular Simulation Package, Version 2.18”, Daresbury laboratory: Daresbury, U.K. (2007).
[13] کشاورزی، ع.، "ترمودینامیک آماری سیالات ماکروسکوپی و محدود شده در فضای نانو"، جهاد دانشگاهی، دانشگاه صنعتی اصفهان، چاپ اول (1390).
[14] Brehm M., Kirchner B., TRAVIS - A Free Analyzer and Visualizer for Monte Carlo and Molecular Dynamics Trajectories, J. Chem. Inf. Model, 51: 2007–2023 (2011).
[15] Humphrey W., Dalke A., Schulten K., VMD: Visual Molecular Dynamics, J. Mol. Graphics, 14: 33-38 (1996).
[18] Cervinka C., Padua A. A. H., Fulem M., Thermodynamic Properties of Selected Homologous Series of Ionic Liquids Calculated Using Molecular Dynamics, J. Phys. Chem. B, 120: 2362−2371 (2016).
[19] Lovelock K. R. J., Deyko A., Corfield J., Gooden P. N., Licence P., Jones R. G., Vaporisation of a Dicationic Ionic Liquid, Chem. Phys. Chem., 10: 337 – 340 (2009).