Thermal effect on C-H stretching vibrations of the imidazolium ring in ionic liquids

被引:126
作者
Yokozeki, A.
Kasprzak, Daniel J.
Shiflett, Mark B.
机构
[1] DuPont Fluoroprod Lab, Wilmington, DE 19880 USA
[2] DuPont Cent Res & Dev, Expt Stn, Wilmington, DE 19880 USA
关键词
D O I
10.1039/b706497g
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
We have studied temperature dependent IR spectra of the C-H stretching modes of the imidazolium ring in [bmim][PF6], [bmim][Tf2N], [emim][Tf2N], [hmim][Tf2N], and [bmim][BF4]. Temperatures in this study are from 278 to 348 K at an interval of 10 K. Spectra of the C-H stretching modes have been deconvoluted using our previous computer program of the Voigtlineshape function. Frequency shifts, Lorentzian spectral widths, and band absorbance were examined as a function of temperature. In order to interpret the observed behaviors, we have developed a simple mechanical model as well as a chemical equilibrium model. The model analyses suggest that enthalpy changes for the cluster and/or ion-pair breaking reactions in the liquid state are several kJ mol(-1) endothermic, and the degree of dissociations of ion pairs or hydrogen bonded clusters is in the range from 0.3 to 0.9 with different magnitudes for the five ionic liquids.
引用
收藏
页码:5018 / 5026
页数:9
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