Voltammetric and physicochemical characterization of hydroxyl- and ether-functionalized onium bis(trifluoromethanesulfonyl)imide ionic liquids

Several hydroxyl- and ether-functionalized binary task specific ionic liquids (ILs) are prepared, ether-functionalized ILs exhibit higher conductivity and lower viscosity than those of hydroxyl-functionalized ILs, whereas hydroxyl-functionalized ILs show wider potential window than those of ether-functionalized ILs. The correlation between ionic conductivity and viscosity is based on the classical Walden rule: a relatively large deviation of the plots from the ideal Walden line is observed for the ILs without considering the ion size, whereas the deviation decreases significantly when the adjusted Walden plot is adopted. The a values of ILs calculated from the slopes of the Walden plots are compared to those calculated from the ratio of activation energies for viscosity and molar conductivity (E-a,E-A/E-a,E-eta). There are very few reports where electrochemically derived activation energy from conductivity and voltammetric characterization are available for comparison, so a key concept of activation energy in electrochemistry could be developed in this paper. (C) 2011 Elsevier Ltd. All rights reserved.