Pentafluoroethyl(fluoro)phosphate ionic liquids: synthesis and properties

Area of Science:

• Materials Science
• Electrochemistry
• Organic Chemistry

Background:

• Ionic liquids (ILs) are versatile solvents with tunable properties.
• Fluorophosphate anions offer unique characteristics for IL applications.
• Understanding structure-property relationships is crucial for designing advanced ILs.

Purpose of the Study:

• Synthesize novel fluorophosphate ionic liquids (FAP ILs).
• Characterize their structural, thermal, physicochemical, and electrochemical properties.
• Investigate the influence of anion structure on IL properties.

Main Methods:

• Synthesis of FAP ILs using tris(pentafluorethyl)difluorophosphorane.
• Characterization via NMR, IR, Raman spectroscopy, and elemental analysis.
• Single crystal X-ray diffraction for structural elucidation.
• Measurement of thermal, physicochemical, and electrochemical properties.
• Density Functional Theory (DFT) calculations for theoretical insights.

Main Results:

• Successful synthesis and characterization of FAP ILs with [EMIm]+, [BMIm]+, and [Pyr14]+ cations.
• Crystal structures of selected [EMIm]+ and [BMIm]+ FAP ILs were determined.
• [BMIm]FAP2 demonstrated the lowest dynamic viscosity and highest specific conductivity among [BMIm]+ ILs.
• Weakly coordinating nature of anions increased: [PF6]- < FAP1 < FAP2 < FAP3.
• Anion size, shape, flexibility, and coordination influenced IL properties.

Conclusions:

• FAP ILs represent a promising class of ionic liquids with tunable properties.
• [BMIm]FAP2 is identified as a potential candidate for applications requiring high conductivity and low viscosity.
• The study provides valuable insights into the structure-property relationships of fluorophosphate-based ionic liquids.