Investigation of lithium chloride/ambient-temperature 1-methyl-3-ethylimidazolium chloride-aluminum chloride ionic liquids. 1. Ion interactions in a neutral tetrachloroaluminate melt

Abstract

Ion interactions in a neutral ambient-temperature tetrachloroaluminate melt were studied using FTIR and NMR techniques at different lithium concentrations. The effect of lithium on the imidazolium cation is shown to be very small, but it strongly affects the AlCl4 - anion, leading to the perturbation of the Td symmetry and the appearance of extra absorption peaks due to lithium interactions. The interactions are strong in the LiCl-ImCl-AlCl3 melt, and the absorbances of the related vibration peaks are linearly dependent on the lithium concentration. Under high Li+ concentrations, an obvious change in the conductivity, density, viscosity, and 7Li NMR shifts is observed when the mole ratio of AlCl4 -:Li+ is less than 3.5:1 to 5:1, depending on different measuring techniques. A model with the formation of a network-like structure of Li+/AlCl4 - under high Li+ concentrations was proposed to explain the above changes. © 1995 American Chemical Society.