Preparation of [Al(hfip)4]-Based Ionic Liquids with Siloxane-Functionalized Cations and Their Physical Properties in Comparison with Their [Tf2N] Analogues


  • (hfip=(CF3)2CH[BOND]O)


Two new ionic liquids (ILs) with siloxane-functionalized cations and the weakly coordinating tetraalkoxyaluminate [Al(hfip)4] (hfip=hexafluoroisopropoxy) are prepared and characterized by nuclear magnetic resonance (NMR), infrared (IR) and Raman spectroscopy. With melting points below 0 °C they qualify as room temperature ILs (RTILs). Their temperature-dependent viscosities and conductivities, together with those of two [Tf2N] ILs with the same cations and a further siloxane-functionalized [Tf2N] IL, are measured between 0 and 80 °C, and all are described by the Vogel–Fulcher–Tammann (VFT) equations. We note that the [Al(hfip)4] ILs have lower viscosities than their [Tf2N] analogues at all measured temperatures and higher conductivities at room temperature.