Spontaneous polyiodide formation by unbalancing of charge in room-temperature ionic liquid-lithium salt solutions

Peculiar High-Pressure Phase Behavior of 1-Butyl-3-methylimidazolium Iodide

We investigated the stability of the liquid phase of 1-butyl-3-methylimidazolium iodide (hereafter abbreviated as [C₄mim][I]) up to 16.7 GPa at room temperature. We observed a peculiar phase transition behavior in the [C₄mim][I] sample. In particular, a glassy state was formed at ∼1.3 GPa; however, the reddish-brown precipitate was formed probably due to concentrated I₃^- or I₂^- species that were formed above 12 GPa; [C₄mim][I] showed a pressure-induced partial crystallization from the glassy state. We concluded that the conformation of [C₄mim]⁺ is essential in iterative modulation to control the environmental formation of iodide precipitate.

Lithium-triggered spontaneous formation of polyiodides in room-temperature ionic liquid-alcohol solutions

In this study, the effect of alcohol on polyiodide formation in room-temperature ionic liquid (RTIL) was examined by time evolutions of Raman spectra in the low-frequency region and by color changes of the sample. The RTIL was 1-methyl-3-propylimidazolium iodide, [C₃mim][I]. Polyiodides develop in [C₃mim][I]‑lithium salt-ethanol solutions (Abe et al., Chem. Phys. 502 (2018) 72.). Without the external addition of iodine or without an external electric field, the irreversible transformation from I^- to I₃^- indicates that charge unbalancing was promoted by lithium ion. Polyiodide formations were not induced by sodium or potassium ions. Strong alcohol effects were observed directly by the time-dependent Raman bands in the low-frequency region.