title: Preparation of colorless ionic liquids "on water" for spectroscopy.
abstract: Although colorless ionic liquids (ILs) are most desirable, as synthesized they frequently bear color, despite appearing pure by most analytical techniques. It leads to some uncertainties and limits for the fundamental research and applications of ILs, such as spectroscopy. Using 1-butyl-3-methylimidazolium bromide (BMIMBr), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF(4)) and 1-hexyl-3-methylimidazolium bromide (HMIMBr) as models, we demonstrated that following classic preparing method except that the water was added as solvent, colorless ILs could be facilely prepared. Neither critical pre-treatment of starting materials and pre-cautions during the reaction nor time-consuming and costly post-decolor-purification was needed. The effects of "on water" reaction conditions on preparing colorless IL and the reason why using water as solvent could produce colorless ILs were also preliminary investigated. It was found that the reactant solubility played an important role in the preparation of colorless ILs. Not only as a method to evaluate the quality of as-synthesized ILs, but also as a spectroscopic analytical applications, UV-vis spectra showed that the ILs by this "on water" method was spectral pure and sufficient for future fundamental spectroscopic research and applications.
authors.affiliation: State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, and Graduate School of the Chinese Academy of Sciences, Chinese Academy of Sciences, Renmin St. 5625, Changchun 130022, PR China.
authors.forename: Yanfei
authors.initials: Y
authors.lastname: Shen
authors.forename: Yuanjian
authors.initials: Y
authors.lastname: Zhang
authors.forename: Dongxue
authors.initials: D
authors.lastname: Han
authors.forename: Zhijuan
authors.initials: Z
authors.lastname: Wang
authors.forename: Daniel
authors.initials: D
authors.lastname: Kuehner
authors.forename: Li
authors.initials: L
authors.lastname: Niu