1-Alkyl-3-methylbenzotriazolium salts: ionic solvents and electrolytes

Abstract

A series of 1-alkyl-3-methylbenzotriazolium halides were synthesised and purified by recrystallisation. Novel salts of these benzotriazolium cations were obtained by metathesis with a number of diverse anions including: dicyanamide N(CN)₂, mesylate CH₃SO₃, tosylate CH₃C₆H₄SO₃ and bis(trifluoromethane)sulfonamide N(SO₂CF₃)₂. Thermal analyses of these very stable salts included the determination of glass transition temperatures (−65 to −12 °C), melting points (29 to 143 °C), entropies of fusion (14 to 69 J K⁻¹ mol⁻¹) and decomposition temperatures (up to 315 °C). Electrochemical analyses show electrochemical windows of up to ≈3.5 V, the cation producing electrochemical reduction reactions below −1 V (Ag/Ag⁺). Solubility data for a range of organic compounds dissolved in the new ionic liquids and for comparison in some more common ionic liquids are also provided.