Complexation characteristics of 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6, 18C6) with Li+ and K+ in a hydrophobic ionic liquid of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide under dry and humid conditions at 298.2 K were studied by 1H and 13C NMR chemical shifts. The comparison of the 1H and 13C chemical shifts of 18C6 molecule between the dry and humid IL solutions without the alkali metal ions showed that uncomplexed 18C6 molecules are solvated by water molecules in the humid ionic liquid solution. The changes in the 1H and 13C chemical shifts of 18C6 ligand molecule with the increases in the Li+ and K+ concentrations revealed that in both dry and humid ionic liquid solutions 18C6 molecule forms 1:1 complexes with Li+ and K+. The 1H NMR data of water molecules in the humid ionic liquid solutions demonstrated that water molecules interact with Li+-18C6 complexes and free Li+, but do not with K+-18C6 complexes and free K+. The mechanisms of the formation of the Li+ and K+ complexes in the humid ionic liquid solution are different from each other due to the differences in the complex-water interactions.

中文翻译：

---

疏水性1-乙基-3-甲基咪唑鎓双(三氟甲磺酰基)酰胺离子液体中水在1,4,7,10,13,16-六氧杂环十八烷(18-冠-6)与Li+和K+络合中的作用


1,4,7,10,13,16-六氧杂环十八烷(18-冠-6, 18C6)与Li+和K+在1-乙基-3-甲基咪唑鎓双(三氟甲磺酰基)酰胺疏水性离子液体中干燥和络合特性通过 1H 和 13C NMR 化学位移研究了 298.2 K 的潮湿条件。干燥和不含碱金属离子的潮湿IL溶液之间18C6分子的1H和13C化学位移的比较表明，未络合的18C6分子被潮湿离子液体溶液中的水分子溶剂化。 18C6配体分子的1H和13C化学位移随着Li+和K+浓度的增加而变化，表明在干燥和潮湿的离子液体溶液中18C6分子与Li+和K+形成1:1配合物。潮湿离子液体溶液中水分子的1H NMR数据表明，水分子与Li+-18C6配合物和游离Li+相互作用，但不与K+-18C6配合物和游离K+相互作用。由于络合物-水相互作用的差异，在潮湿的离子液体溶液中形成Li+和K+络合物的机制彼此不同。