Elucidating the iron-based ionic liquid [C4py][FeCl4]: structural insights and potential for nonaqueous redox flow batteries

Christian Balischewski, Biswajit Bhattacharyya*, Josh J. Bailey, Scott D. Place, Peter Nockemann, Jiyong Kim, Armin Wedel, Shashank Gahlaut, Ilko Bald, Weiyang Li, Yann Garcia, Eric Sperlich, Christina Günter, Alexandra Kelling, Andreas Taubert*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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In this study, a low-melting organic-inorganic crystalline ionic liquid compound, N-butyl pyridinium tetrachlorido ferrate (III) is described. The material can easily be synthesized using a one-pot approach in an ionic liquid medium. Single-crystal X-ray diffraction confirms that the basic inorganic block is [FeCl4], which is counterbalanced by an N-butyl pyridinium cation. The compound exhibits a melting point of 37.6 °C by differential scanning calorimetry, which is among the lowest values for a pyridinium-based metal-containing ionic liquid. The material shows promising electrochemical behavior at room temperature in both aqueous and nonaqueous solvents, and at elevated temperatures in its pure liquid state. Given its appreciable solubility in both water and acetonitrile, the compound can act as a redox-active species in a supporting electrolyte for redox flow battery applications. These classes of low-melting ionic solids with long-range order and interesting electrochemical applications are potential candidates for a range of green energy storage and harvesting systems.

Original languageEnglish
Article number2311571
Number of pages10
JournalAdvanced Functional Materials
Issue number12
Early online date14 Dec 2023
Publication statusPublished - 18 Mar 2024


  • chloridoferrate(III)
  • Ionic liquids
  • redox flow battery

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • General Chemistry
  • Biomaterials
  • General Materials Science
  • Condensed Matter Physics
  • Electrochemistry


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