Pressure-induced phase transition of 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF₆]

An Infrared Spectroscopy Study of the Conformational Evolution of the Bis(trifluoromethanesulfonyl)imide Ion in the Liquid and in the Glass State

“…For instance, in analogy with cold crystallization usually observed when supercooled ionic liquids are reheated, high pressure Raman experiments showed that two different ionic liquids based on the [BF 4 ] − anion can be pressurized above 5.0 GPa at room temperature, undergoing crystallization after releasing the 2 Advances in Condensed Matter Physics pressure below ∼2.0 GPa [9][10][11][12][13]. Moreover, N,N-diethyl-Nmethyl-N-(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide does not crystallize up to 5.0 GPa at room temperature, but a pressure-induced change in the structural organization might occur around this pressure range [9][10][11][12]. Other studies detected below 1.0 GPa the presence of liquidcrystal and crystal phase transitions of imidazolium based ILs, having different anion, that is, Cl − , Br − , and PF 6 − [14,15].…”

Structural organization and phase behaviour of 1-butyl-3-methylimidazolium hexafluorophosphate: an high pressure Raman spectroscopy study

“…38 After acceptance of the manuscript, we became aware of the very recent work from Takekiyo and coworkers reporting on the detection of one crystalline phase for [bmim] [PF 6 ] under high pressure conditions. 39 This crystalline phase corresponds to the one that we identify as Solid_1 in the present manuscript. …”

Pressurizing the mixtures of two ionic liquids: Crystallization versus vetrification

“…Usually, the concentration of the conformers with lower volume increases upon compression. Typically, a decrease of the volume of ~1–2 cm 3 /mol is observed . The variation of populations of conformers of the imidazolium cations was also investigated by means of molecular dynamics simulations .…”

“…Phase transitions have been identified by various methods: a slope change of the pressure dependence of some vibrational wavenumbers; the broadening of the fluorescence lines emitted from the ruby spheres used for measuring pressure; the appearance of a frozen dynamics below 100 cm −1 , in the case of glass transition; and the change in the population of different conformers of ions . As to the latter method, most studies were performed on ILs containing imidazolium‐based cations, which possess isomers, and anions, which do not possess conformers, such as BF 4 , PF 6 , NO 3 , and TfO . Indeed, the alkyl chain attached to the imidazole ring has many flexible CC bonds, and, therefore, a large number of conformers are present in the ILs.…”