A series of TiCl4-based ionic liquids (ILs) was synthesized by mixing TiCl4 with quaternary ammonium, pyridinium, and imidazolium chlorogenated salt, respectively. The structure and composition of the ILs were studied with Fourier transform ion cyclotron resonance mass spectrometry. IR, and Raman spectra. The primary anions of the TiCl4-based ILs were TiCl9- and TiCl62-, whose amounts were different by variation of the molar ratio of TiCl4 to organic halogenated salt. The physical properties such as the phase transition behavior, surface tension, density, viscosity, and conductivity of these ILs were also investigated. Temperature-dependent viscocity and conductivity of the ILs followed the Vogel-Tammann-Fulcher equation, and the best-fit parameters had been estimated, together with the lienar fitting parameters for the density. The conductivity and viscosity of the TiCl4-based ILs were controlled by the ion mobility and the availability of voids with suitable dimensions. Hole theory could well explain the physicochemical properties of the TiCl4-based ILs. (c) 2008 The Electrochemical Society. [DOI: 10.1149/1.3046160] All rights reserved.