用核磁共振技术研究[C4mim][BF4]在重水和氘代氯仿中的聚集行为

运用核磁共振技术, 研究了室温离子液体1-丁基-3-甲基咪唑四氟硼酸盐(C4mim]BF4])在重水和氘代氯仿中的聚集行为. 实验结果表明, 随着混合体系中离子液体摩尔分数的增加, 在重水中, 离子液体阳离子上各氢原子的化学位移向低场移动, 且呈现了先急剧变化, 后趋于平缓的变化趋势; 在氘代氯仿中, 离子液体阳离子上H2的化学位移向高场移动, H4和H5以及与氮原子直接相连的甲基和亚甲基上的氢原子的化学位移都向低场移动, 且各氢原子的核磁共振信号发生了变化. 根据质量作用定律及1H NMR化学位移随浓度的变化关系计算了C4mim]BF4]在重水中的临界聚集浓度和聚集数, 并在离子液体阴、阳离子缔合以及离子液体与溶剂相互作用的基础上对实验结果进行了讨论.

NMR Study on the Aggregation of [C4mim][BF4] in D2O and CDCl3

Aggregation behavior of the room temperature ionic liquid (IL) C4mim]BF4] in D2O and CDCl3 was studied by the nuclear magnetic resonance (NMR) technique. Results indicated that proton chemical shifts for the cation of the IL shift downfield as the molar fraction of IL increases. These proton chemical shifts change rapidly at lower concentrations and level off at higher concentrations in D2O. Chemical shifts for H2 on the cation shift upfield. H4, H5, methyl and methylene protons next to the nitrogen of the cation shift downfield as the molar fraction of IL increases while the NMR signals for each proton changes in CDCl3. The critical aggregation concentration (CAC) and the aggregation number were determined by applying mass action theory to the concentration dependence of the 1H NMR chemical shifts. These results are discussed based on the interactions between the cation and the anion and those between the IL and the solvents.