Fluorosulfonyl-(trifluoromethanesulfonyl)imide ionic liquids with enhanced asymmetry

New ionic liquids with an asymmetric anion, fluorosulfonyl-(trifluoromethanesulfonyl)imide (FTFSI), were prepared and their chemical-physical properties were investigated. The ionic liquids based on N-methyl-N-propylpyrrolidinium, PYR13, N-butyl-N-methylpyrrolidinium, PYR14, and N-methoxyethyl-N-methylpyrrolidinium, PYR12O1, exhibit high electrochemical stability (>5.5 V on platinum) and thermal stability (>250 degrees C in N-2 and >200 degrees C in O-2). Due to the highly asymmetric anion, the prepared ionic liquids do not crystallize down to -150 degrees C while maintaining ionic conductivity above 10(-4) S cm(-1) even at -40 degrees C. Conductivity and viscosity values at 20 degrees C are in the range 3.5-5.0 mS cm(-1) and 30-60 mPa s respectively. PFG-NMR measurements showed high self-diffusion coefficients of cations and the anion.