Conformational preferences of two imidazolium-based ionic liquids at high pressures

High Pressure Phase Behavior of Two Imidazolium-Based Ionic Liquids, [bmim][BF4] and [bmim][PF6]

“…We note that further compression up to 2.0 GPa induces two more changes in the I gt /I tt ratio, implying the existence of other high-pressure crystalline phase transitions in agreement with the results as shown in section 3.1. On the other hand, as to the [bmim] [BF 4 ], the value of I gt /I tt slightly increases with applied pressure as shown in Figure 13, i.e., the gt conformer is also a dominant specie and stabilized under high pressure (Takekiyo et al, 2011). Therefore, the predominance of the gt conformer under high pressure seems to be less dependent on the anionic species such as PF 6¯, BF 4¯ (Takekiyo et al, 2011), andCl¯ (Change et al, 2007).…”

“…On the other hand, as to the [bmim] [BF 4 ], the value of I gt /I tt slightly increases with applied pressure as shown in Figure 13, i.e., the gt conformer is also a dominant specie and stabilized under high pressure (Takekiyo et al, 2011). Therefore, the predominance of the gt conformer under high pressure seems to be less dependent on the anionic species such as PF 6¯, BF 4¯ (Takekiyo et al, 2011), andCl¯ (Change et al, 2007). In relation to this, previous Raman and IR studies of simple organic liquids such as dihaloethane (Taniguchi et al, 1981), halopropane (Kato & Taniguchi, 1990), and n-alkane in neat solution (Kato & Taniguchi, 1991;Schoen et al, 1979) show that the gauche conformer is more stable than the trans conformer under high pressure.…”

High-pressure phase behavior of the room temperature ionic liquid 1-ethyl-3-methylimidazolium nitrate

“…In addition, its estimated (glass) transition pressure (p g ) amounted to approximately 2. 8 3 ], which relates to molecular packing and variations in ion-pair interactions [24], may induce dissimilar phase stabilities at high pressures. Repulsive forces are also important in molecular liquids and may similarly impact RTILs.…”

“…Because of the direct correlation between the specific phase behavior of RTILs and the isomerism of the imidazolium cation [9,24,26,27], the conformational changes of this cation were investigated according to the pressure-induced phase changes. Planar (P)-nonplanar (Np) Pressure /GPa CH stretching frequency /cm -1 equilibrium shifts for the C2N1C7C8 angle of the ethyl chain are reflected in the Raman spectrum detected from 400 to 460 cm − 1 .…”

Ionic liquid; possibility of protein-preserving solvent under high pressure

“…In our primary work, we showed that aqueous IL solutions easily form a glassy state at low temperature (77 K) in wider concentration range compared with conventional aqueous salt solutions [5]. Besides, some of the imidazolium-based ILs does not crystallize even by compression up to 2.0 GPa [6,7]. We also figured out that a certain aqueous IL solution in the IL-rich condition induces partial refolding of once unfolded proteins [8].…”