Synthesis, Physical and Ion-Conducting Properties of 1,2,3-Triazolium Ionic Liquids

1,4-Disubstituted 1,2,3-triazoles are readily obtained by copper(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC)-the most widespread illustration of click chemistry to date. 1,2,3-Triazoles form a vast and easily accessible library of precursors for synthesizing 1,2,3-triazolium ionic liquids (TILs). A series of four 1,3,4-trisubstituted TILs with N-1-n-octyl, N-3-methyl and different C-4 substituents (i.e., aromatic, aliphatic, PEGylated and perfluorinated groups) is synthesized in two steps involving: (i) CuAAC to generate 1,2,3-triazole precursors and (ii) N-alkylation of the 1,2,3-triazole groups with methyl iodide to afford the corresponding 1,2,3-triazolium salts with iodide counter-anions. A thorough investigation of the correlations between structure and properties is carried out using NMR spectroscopy, high-resolution mass spectrometry, differential scanning calorimetry, thermogravimetric analysis and broadband dielectric spectroscopy. The PEGylated TIL has also undergone ion metathesis to produce the TIL analogue with a bis(trifluoromethylsulfonyl)imide counter-anion. Of all the synthesized TILs, this derivative exhibits the lowest glass transition temperature (T_g = -76 °C), the highest thermal stability (T_d10 = 345 °C) and the greatest ionic conductivity (σ_DC = 6.5 × 10^-4 S cm^-1 at 30 °C under anhydrous conditions).