Ion-pair formation in the ionic liquid 1-ethyl-3-methylimidazolium bis(triflyl)imide as a function of temperature and concentration

被引:301
作者
Koeddermann, Thorsten [1 ]
Wertz, Christiane [1 ]
Heintz, Andreas [1 ]
Ludwig, Ralf [1 ]
机构
[1] Univ Rostock, Inst Chem, Chem Phys Abt, D-18051 Rostock, Germany
关键词
density functional calculations; hydrogen bonds; ion pairs; ionic liquids; IR spectroscopy;
D O I
10.1002/cphc.200600034
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
The structures and ion-pair formation in the ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide are studied by a combination of FTIR measurements and DFT calculations. We could clearly distinguish imidazolium cations that are completely H-bonded to anions from those that are single H-bonded in ion pairs. Ion-pair formation already occurs in the neat IL and rises with temperature. Ion-pair formation is strongly promoted by dilution of the IL in chloroform. In these weakly polar environments ion pairs H-bonded via C(2)H are strongly favored over those H-bonded via C(4,5)H. This finding is in agreement with DFT (gas phase) calculations, which show a preference for ion pairs H-bonded via C(2)H as a result of the acidic C(2)H bond.
引用
收藏
页码:1944 / 1949
页数:6
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