Comparison of Polarities of Room-Temperature Ionic Liquids Using FT-IR Spectroscopic Probes

Guo-hong Tao; Ming Zou; Xiao-hua Wang; Zhi-yu Chen; David G. Evans; Yuan Kou

doi:10.1071/CH05025

RESEARCH ARTICLE

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Comparison of Polarities of Room-Temperature Ionic Liquids Using FT-IR Spectroscopic Probes

Guo-hong Tao ^A , Ming Zou ^A , Xiao-hua Wang ^A , Zhi-yu Chen ^A , David G. Evans ^A and Yuan Kou ^A ^B

+ Author Affiliations

- Author Affiliations

^A State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.

^B Corresponding author. Email: yuankou@pku.edu.cn

Australian Journal of Chemistry 58(5) 327-331 https://doi.org/10.1071/CH05025
Submitted: 8 January 2005 Accepted: 17 March 2005 Published: 1 May 2005

Abstract

The solvent properties, especially the polarity, of room-temperature ionic liquids (RTILs) of the general type [Cnmim]X, where [C_nmim] is the 1-C_nH_2n+1-3-methylimidazolium cation and X is [BF₄]⁻, [PF₆]⁻, [NO₃]⁻, [SCN]⁻, or [NTf₂]⁻ (Tf = CF₃SO₂), have been investigated using Fourier-transform infrared (FTIR) spectroscopy. Comparing the experimental shifts in the ν_C=O stretching frequencies of acetone and N,N-dimethylformamide (DMF) as probe molecules suggests that the polarities of most common RTILs are between that of DMF and methanol. A more sensitive probe, Fe(CO)₅, can distinguish small polarity differences between RTILs with similar structures. The effects of varying the structure of RTILs by introducing functional groups and different anions on their polarity are also compared.

Acknowledgments

This research was supported by the ‘973’ Program of the Chinese Ministry of Science and Technology under contract number G-2000048002.

References

Comparison of Polarities of Room-Temperature Ionic Liquids Using FT-IR Spectroscopic Probes

Abstract

Acknowledgments

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