Preparation of [Al(hfip) _4] ~--based ionic liquids with siloxane-functionalized cations and their physical properties in comparison with their [Tf _2N] - analogues

摘要

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 [Tf _2N] ~- ILs with the same cations and a further siloxane-functionalized [Tf _2N] ~- 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 [Tf _2N] ~- analogues at all measured temperatures and higher conductivities at room temperature.