Preparation of [Al(hfip)4](-)-based ionic liquids with siloxane-functionalized cations and their physical properties in comparison with their [Tf2N]- analogues.

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(2)N](-) ILs with the same cations and a further siloxane-functionalized [Tf(2)N](-) 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(2)N](-) analogues at all measured temperatures and higher conductivities at room temperature.

Understanding the polarity of ionic liquids.

The polarities of a wide range of ionic liquids have been determined using the Kamlet-Taft empirical polarity scales α, ß and π*, with the dye set Reichardt's Dye, N,N-diethyl-4-nitroaniline and 4-nitroaniline. These have been compared to measurements of these parameters with different dye sets and to different polarity scales. The results emphasise the importance of recognising the role that the nature of the solute plays in determining these scales. It is particularly noted that polarity scales based upon charged solutes can give very different values for the polarity of ionic liquids compared to those based upon neutral probes. Finally, the effects of commonplace impurities in ionic liquids are reported.