Six novel ionic liquids based on benzotriazolium ion were synthesized by an improved method. These ionic liquids were characterized by IR, H-1 NMR, and elemental analysis. Their melting point, thermal stability, conductivity, electrochemical window and solubility properties in common solvents were investigated. The results indicate that these ionic liquids show the higher thermal stability (up to 345 degrees C), the larger electrochemical window of 3 V, the peculiar solubility in traditional solvents and the excellent electrochemical medium in the electrochemical oxidation of naphthalene and ferrocene. (c) 2005 Elsevier Ltd. All rights reserved.