Cadena Cesar, Zhao Qi, Snurr Randall Q, Maginn Edward J
Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA.
J Phys Chem B. 2006 Feb 16;110(6):2821-32. doi: 10.1021/jp056235k.
A combined experimental and molecular dynamics study has been performed on the following pyridinium-based ionic liquids: 1-n-hexyl-3-methylpyridinium bis(trifluoromethanesulfonyl)imide ([hmpy][Tf(2)N]), 1-n-octyl-3-methylpyridinium bis(trifluoromethanesulfonyl)imide ([ompy][Tf(2)N]), and 1-n-hexyl-3,5-dimethylpyridinium bis(trifluoromethanesulfonyl)imide ([hdmpy][Tf(2)N]). Pulsed field gradient nuclear magnetic resonance spectroscopy was used to determine the self-diffusivities of the individual cations and anions as a function of temperature. Experimental self-diffusivities range from 10(-11) to 10(-10) m(2)/s. Activation energies for diffusion are 44-49 kJ/mol. A classical force field was developed for these compounds, and molecular dynamics simulations were performed to compute dynamic as well as thermodynamic properties. Evidence of glassy dynamics was found, preventing accurate determination of self-diffusivities over molecular dynamics time scales. Volumetric properties such as density, isothermal compressibility, and volumetric expansivity agree well with experiment. Simulated heat capacities are within 2% of experimental values.
1-正己基-3-甲基吡啶双（三氟甲磺酰）亚胺（[hmpy][Tf₂N]）、1-正辛基-3-甲基吡啶双（三氟甲磺酰）亚胺（[ompy][Tf₂N]）和1-正己基-3,5-二甲基吡啶双（三氟甲磺酰）亚胺（[hdmpy][Tf₂N]）。采用脉冲场梯度核磁共振光谱法测定了各个阳离子和阴离子的自扩散系数随温度的变化。实验测得的自扩散系数范围为10⁻¹¹至10⁻¹⁰ m²/s。扩散的活化能为44 - 49 kJ/mol。为这些化合物开发了一个经典力场，并进行了分子动力学模拟以计算动力学和热力学性质。发现了玻璃态动力学的证据，这妨碍了在分子动力学时间尺度上准确测定自扩散系数。诸如密度、等温压缩率和体积膨胀率等体积性质与实验结果吻合良好。模拟的热容在实验值的2%以内。
