EFFECT OF TEMPERATURE ON THE ELECTRICAL CONDUCTIVITY OF CONCENTRATED SOLUTIONS OF 1-BUTYL-4-METHYLPYRIDINIUM TETRAFLUOROBORATE IN ACETONITRILE, DIMETHYLFORMAMIDE, AND DIMETHYL SULFOXIDE

The specific electrical conductivity (EC) of concentrated solutions of 1-butyl-4-methylpyridinium tetrafluoroborate ([BuMPy][BF4]) in acetonitrile (AN) was measured in the temperature range of 10–60 °C and in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in the range of 10–70 °C. The specific EC increases with increasing temperature and passes through a maximum with increasing concentration. The values of the maximum specific EC at a given temperature κmax and the corresponding concentrations cmax were determined. With increasing temperature, the κmax value of [BuMPy][BF4] solutions in AN, DMF, and DMSO increases proportionally to the cmax value. The activation energy Eκ of the specific EN of the studied solutions decreases with increasing temperature and increases with increasing concentration. The specific EC κ of solutions is higher, the higher the limiting high-frequency (HF) EC κ∞ of the solvent. In the series AN – DMF – DMSO, the value of κ∞ decreases, therefore, in this series, the specific EC of [BuMPy][BF4] solutions in these solvents also decreases. At temperatures of 20 – 25 °C, the maximum specific EC is achieved at the same concentrations of [BuMPy][BF4] (1.3 – 1.4 mol/l) in all three solvents (AN, DMF and DMSO). In this case, the highest specific EC (5.0 – 5.5 S/m) occurs in AN solutions, and the lowest (1.5 – 1.7 S/m) – in DMSO solutions. An increase in temperature to 60–70 °C leads to a shift in the maximum of the specific EC to concentrations of 1.6–1.8 mol/l, and the EC value increases to 7.6 S/m in AN solutions and to 3.8 S/m in DMSO solutions. It was found that at concentrations not exceeding ~1.0 mol/l with increasing temperature the specific electrical conductivity κ of [BuMPy][BF4] solutions in AN, DMF and DMSO increases directly proportionally to the limiting HF EC κ∞ of the solvent. In this case, the values of the specific EC of [BuMPy][BF4] solutions in AN and DMSO are placed on one straight line at equal concentrations. Based on the analysis of the κ – κ∞ dependencies, the solvation numbers of [BuMPy][BF4] were determined, which coincide for [BuMPy][BF4] solutions in AN and DMF. For citation: Artemkina Yu.M., Odinaev U.N., Dzyuba V.Yu., Shcherbakov V.V. Effect of temperature on the electrical conductivity of concentrated solutions of 1-butyl-4-methylpyridinium tetrafluoroborate in acetonitrile, dimethylformamide, and dimethyl sulfoxide. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2025. V. 68. N 6. P. 29-40. DOI: 10.6060/ivkkt.20256806.7196.