Ionic liquids were synthesised that consisted of two methylimidazolium rings joined by a spacer 1-12 carbon atoms in length. The bis(triflic)imides with spacer <= C-4 were solids; the others were liquid at room temperature. The polarity of the dication liquids and their performance in the extraction of phenol from water were compared with those of similar monocationic liquids. (c) 2005 Society of Chemical Industry