Raman and FTIR Spectroscopic Studies of 1‐Ethyl‐3‐methylimidazolium Trifluoromethylsulfonate,its Mixtures with Water and the Solvation of Zinc Ions |
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| Authors: | Zhen Liu Prof Dr Sherif Zein El Abedin Prof Dr Frank Endres |
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| Institution: | 1. Institute of Electrochemistry, Clausthal University of Technology, Arnold‐Sommerfeld‐Strasse 6, Clausthal‐Zellerfeld (Germany). 38678 address:;2. Electrochemistry and Corrosion Laboratory, National Research Centre, Dokki, Cairo (Egypt) |
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| Abstract: | In this paper we report on the interactions of the ionic liquid 1‐ethyl‐3‐methylimidazolium trifluoromethylsulfonate (EMIm]TfO) with water and the solvation of zinc ions in neat EMIm]TfO and EMIm]TfO–water mixtures investigated by FTIR and Raman spectroscopy. The structures and physicochemical properties of the EMIm]TfO–water mixtures are strongly dependent on the interaction between cations, anions, and water. The structure was changed from ionic‐liquid‐like to water‐like solutions upon addition of water. In addition, zinc salts can precipitate in 0.2 M Zn(TfO)2/EMIm]TfO upon addition of 10 % (v/v) water, presumably as a result of polarity change of the solution. The average coordination number of TfO? per zinc ion calculated from Raman spectra is 3.8 in neat EMIm]TfO, indicating that Zn(TfO)4]2?, and Zn(TfO)3]? complexes are present in the solution. However, in the presence of water, water interacts preferentially with the zinc ions, leading to aqueous zinc species. The solvation of zinc ions in 1‐butyl‐1‐methylpyrrolidinium trifluoromethylsulfonate (Py1,4]TfO) was also investigated. In Py1,4]TfO, there are, on average, 4.5 TfO? anions coordinating each zinc ion, corresponding to the weak interaction between Py1,4]+ cations and TfO? anions. The species present in Py1,4]TfO are likely a mixture of Zn(TfO)4]2? and Zn(TfO)5]3?. |
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| Keywords: | ionic liquids IR spectroscopy Raman spectroscopy solvation water |
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