Electrical Conductivity and Association of 1-butyl-3-methylpyridinium bis{(trifluoromethyl)sulfonyl}amide in Some Polar Solvents

The influence of alternating current frequency in the determination of the electrical conductivity of ionic liquids’ (ILs) dilute solutions in polar solvents has been considered. The frequency ranges in which the influence of polarization processes on electrodes occur and ionic relaxation occurs in the bulk of the solution have been excluded from the results of the electrical conductivity measurements. The association constants for Ka ILs in polar solvents published in literature were analyzed. A discrepancy between the values of Ka was noted, which is associated with the use of different calculation equations for electrical conductivity and the insufficiently correct consideration of the frequency dependance of the measured resistance. Based on the measured values of the electrical conductivity of dilute solutions of 1-butyl-3-methylpyridinium bis{(trifluoromethyl)sulfonyl}amide ([Bmpy][NTf2]) in acetonitrile (AN), dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) in the 20--65 °C temperature range, the thermodynamic characteristics of the [Bmpy][NTf2] association were determined. The effect of temperature on the molar electrical conductivity of [Bmpy][NTf2] at infinite dilution λ0 and the association constant Ka have been considered. The Walden product (λ0η), where η is the viscosity of the solvent, was also analysed. It was shown that in AN, DMSO, and DMF, λ0η changes in different ways with increasing temperature; however, the value of λ0η/(εT) corrected for permittivity ε and absolute temperature T does not depend on the temperature and nature of the solvent. As the temperature rises, the electrical conductivity of the dilute solutions of [Bmpy][NTf2] increases in direct proportion to the ratio of the permittivity to dipole dielectric relaxation time of the solvent