The Structures of alkylimidazolium fluorohydrogenate molten salts studied by high-energy X-ray diffraction

Hagiwara, Rika*; Matsumoto, Kazuhiko*; Tsuda, Tetsuya*; Ito, Yasuhiko*; Kohara, Shinji*; Suzuya, Kentaro; Matsumoto, Hajime*; Miyazaki, Yoshinori*

The structures of a series of XF2.3HF (X= 1-methylimidazolium (MI), 1-ethyl-3-methylimidazolium (EMI), 1-butyl-3-methylimidazolium (BMI), 1-hexyl-3-methyl-imidazolium (HMI)) room temperature molten salts have been investigated by high-energy synchrotron X-ray diffraction technique. The correlation peaks appeared in the total correlation function are mainly ascribed to intra-molecular correlation of alkylimidazolium cations. However, it is suggested that the peak at around 3.6 is ascribed not only to intra-molecular but also inter-molecular correlation of the cation. The contribution of the latter is also supported by the first sharp diffraction peak of the total structure factor found at almost the same position as that of a Bragg peak in the simulated X-ray diffraction pattern of solid EMIFHF with a layered structure, corresponding to the layer separation of