X-ray Photoelectron Spectroscopy of 1-Butyl-2,3-Dimethylimidazolium Ionic Liquids: Charge Correction Methods and Electronic Environment of the Anion

Abstract

In this study, six 1-butyl-2,3-dimethylimidazolium ionic liquids are analyzed by X-ray photoelectron spectroscopy. A reliable fitting model is developed for the C 1s region. The charge correction method is discussed in detail. It suggests that the aliphatic carbon component can be used as an internal reference only if the Kamlet-Taft hydrogen bond acceptor ability value is larger than 0.57. The electronic environment of each anion-based component is compared to that of 1-butyl-3-methylimidazolium ionic liquids. It is found that noticeable binding energy shift can be observed in the spectra of S 2p for [TfO]– and P 2p for [PF6]–.