Electrochemistry of Zirconium Tetrachloride in the Ionic Liquid N‐Butyl‐N‐methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide: Formation of Zr(III) and Exploitation of ZrCl₄ as a Facile Ionic Liquid Drying Agent

Abstract

The electrochemistry of zirconium tetrachloride in the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide has been studied, and the one electron reduction is proved by chronoamperometry. Furthermore, we report the application of ZrCl 4 as a facile and general ionic liquid drying agent for use in voltammetry. [3]. Ionic liquids (ILs) are important media for the electrochemical research of species which cannot be studied in aqueous solution. ILs not only have much wider electrochemical windows than regular solvents, often wider than 6 V [2] and thus allowing for electrodeposition of various semiconductors and metals [4], but they also can stabilise some compounds that would normally undergo hydrolysis in aqueous solutions, allowing for studies on water-sensitive species such as PCl 3 [5].In this work, we report the electrochemistry of zirconium tetrachloride (ZrCl 4 ) in the ionic liquid N-butyl-Nmethylpyrrolidinium bis(trifluoromethylsulfonyl)imide [C 4 mpyrr][NTf 2 ]. ZrCl 4 is the main source for production of Zr metal and Zr-based alloys [6], which are important materials and have been widely used in applications such as corrosion-resistant materials, as well as catalysts for various processes [7]. Little data on the electrochemistry of ZrCl 4 in ionic liquids has been hitherto reported. This paucity of information likely arises from its volatility and rapid hydrolysis. ZrCl 4 is readily volatile and very sensitive to air, which makes it difficult to study electrochemically in any detail. To the best of our knowledge, only Tsuda et al. have reported the electrochemistry of Zr(IV) in aluminium chloride-1-ethyl-3-methylimidazolium chloride (66.7-33.3 mol %, respectively) at 353 K [8]. However, since more and more air and moisture stable ILs have been synthesized, there is much interest in non-haloaluminate room temperature ionic liquids. The present study reports not only the electrochemistry of ZrCl 4 but also its application as a facile ionic liquid drying agent. Figure 1 shows the voltammetry of ZrCl 4 in [C 4 mpyrr]-[NTf 2 ], after being dried under vacuum prior to measurement. A limiting reduction current with a half-wave potential of 0.08 V and an oxidation peak current with a peak potential of 0.70 V are clearly visible. Interestingly, the oxidation peak remains the same size as a function of time under vacuum, while the charge under the peak remained constant over a range of scan rates and had a charge characteristic with a monolayer (see below). In contrast the reduction wave steadily decreased over time, since the ZrCl 4 concentrations could not be stabilised in the ionic liquid even if it was put under vacuum for drying for 24 h beforehand, as it both undergoes rapid hydrolysis and is extremely volatile. Thus additions of various concentrations of ZrCl 4 resulted in reductive voltammetry that did not scale with concentration and a white precipitate was always present regardless the concentra-210

Voltammetric analysis of luminescent markers in gunshot residues

“…For both (btc) and Zirconium, the voltammograms presented peaks resembling the peaks of the complex [(Eu 2 Zr)(btc) 3 (Hbtc) 0.5 .6H 2 O] in 0.44 V (vs Ag/AgCl), but do not present the peak in 0.75 V (vs Ag/ AgCl), while europium solution did not present peaks in this analysis. The authors believe that voltammetric signals observed for Zr are due to the one electron process Zr(IV)/Zr(III), which is in good accordance with the previous information observed in the literature [30,31]. The voltammograms in Figure 5, where (btc) and Zr were combined by a solid mixture, showed a higher amperometric…”