Carboxyl-Functionalized Task-Specific Ionic Liquids for Solubilizing Metal Oxides

Imidazolium, pyridinium, pyrrolidinium, piperidinium, morpholinium, and quaternary ammonium bis(trifluoromethylsulfonyl)imide salts were functionalized with a carboxyl group. These ionic liquids are useful for the selective dissolution of metal oxides and hydroxides. Although these hydrophobic ionic liquids are immiscible with water at room temperature, several of them form a single phase with water at elevated temperatures. Phase separation occurs upon cooling. This thermomorphic behavior has been investigated by 1H NMR, and it was found that it can be attributed to the temperature-dependent hydration and hydrogen-bond formation of the ionic liquid components. The crystal structures of four ionic liquids and five metal complexes have been determined.

咪唑鎓（Imidazolium）、吡啶鎓（Pyridinium）、吡咯烷鎓（Pyrrolidinium）、哌啶鎓（Piperidinium）、吗啉鎓（Morpholinium）以及季铵（Quaternary ammonium）类双(三氟甲磺酰基)亚胺（bis(trifluoromethylsulfonyl)imide）盐均经羧基官能化修饰。此类离子液体可用于金属氧化物与氢氧化物的选择性溶解。尽管该类疏水离子液体在室温下与水不互溶，但部分品种在升温条件下可与水形成均相体系，降温后则发生相分离。其温变相行为已通过核磁共振氢谱（¹H NMR）开展研究，结果显示该行为可归因于离子液体组分随温度变化的水合作用与氢键形成过程。已解析得到四种离子液体及五种金属配合物的晶体结构。