ESR spin probes in ionic liquids.
ESR spin probes in ionic liquids.
复制标题
离子液体中的 ESR 自旋探针。
作者：
R. Stoesser;W. Herrmann;A. Zehl;V. Strehmel;A. Laschewsky
在基于取代咪唑鎓阳离子的多种离子液体中检查自旋探针 2,2,6,6-四甲基哌啶-1-氧基 (TEMPO)、4-羟基-2,2,6,6-四甲基哌啶-1-氧基 (TEMPOL) 和 2,2,6,6-四甲基-4-三甲基哌啶-1-羟基碘化物 (CAT-1)分别为四氟硼酸根和六氟磷酸根阴离子。这些系统中自旋探针的重新定向相关时间 tau(R) 已通过完整的光谱模拟确定，并且为了快速重新定向，通过分析电子自旋共振 (ESR) 光谱的超细线的强度来确定。将结果与模型系统甘油/水和选定的有机溶剂的结果进行比较。添加抗磁性和顺磁性离子可以得出这样的结论：盐效应和自旋交换是存在的，并且两者都由运动效应叠加。离子液体中以及自旋探针分子与离子液体成分之间的特定相互作用反映在自旋探针的光谱中，具体取决于它们的分子结构。
The spin probes 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL), and 2,2,6,6-tetramethyl-4-trimethylammoniumpiperidine-1-oxylIodide (CAT-1) are examined in a number of ionic liquids based on substituted imidazolium cations and tetrafluoroborate and hexafluorophosphate anions, respectively. The reorientation correlation times tau(R) of the spin probes in these systems have been determined by complete spectra simulation and, for rapid reortientation, by analysis of the intensities of the hyperfine lines of the electron spin resonance (ESR) spectra. A comparison of the results with those from the model system glycerol/water and selected organic solvents is made. Additions of diamagnetic and paramagnetic ions allow the conclusion that salt effects and spin exchange are present, and that both are superimposed by motional effects. Specific interactions in the ionic liquids, as well as between the spin-probe molecules and the constituents of the ionic liquids are reflected in the spectra of the spin probes, depending on their molecular structure.