The Cybotactic Region Surrounding Fluorescent Probes Dissolved in 1-Butyl-3-methylimidazolium Hexafluorophosphate:  Effects of Temperature and Added Carbon Dioxide

Abstract

We report on the local microenvironment that surrounds three fluorescent solutes (i.e., the cybotactic region) when they are dissolved in a 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF 6 ]) roomtemperature ionic liquid as a function of temperature and added CO 2 (T ) 308 K; P ) 0-150 bar). In dry [bmim][PF 6 ] at 293 K, the cybotactic region exhibits a dielectric constant and refractive index of 11.4 ( 1.0 and 1.523 ( 0.025, respectively. The activation energy that describes the [bmim][PF 6 ] viscous flow is 38.4 ( 0.9 kJ mol -1 . The activation energy for solute rotational reorientation in [bmim][PF 6 ] is equivalent to the activation energy for [bmim][PF 6 ] viscous flow, indicating that solute rotational dynamics are correlated entirely with the [bmim][PF 6 ] dynamics. There is nanosecond dipolar relaxation surrounding a solute dissolved in dry [bmim][PF 6 ] at 293 K. Even though CO 2 is highly soluble in [bmim][PF 6 ] (CO 2 mole fraction ) 0.6 at 313 K and 68 bar), addition of up to 150 bar CO 2 to [bmim][PF 6 ] at 308 K causes the solute's cybotactic region dipolarity to decrease by less than 15%. At a fixed temperature (308 K), we observe a 5-fold decrease in the apparent [bmim][PF 6 ] bulk viscosity between 0 and 150 bar CO 2 .

Electrokinetic chromatographic characterization of novel pseudo‐phases based on N‐alkyl‐N‐methylpyrrolidinium ionic liquid type surfactants

“…It is important to make the distinction that our results do not necessarily suggest that C n MPYB-based micelles are more polar than other micelles, but that they do have a greater ability to interact with polar species relative to virtually all known micelle systems. Previously it was concluded, based on the pyrene I 1 /I 3 index as a measure of the local solvent dipolarity [42,43], that the environment surrounding pyrene solubilized within C 18 MPYB micelles was toluene-like [13]. This point allows us to tentatively suggest a "dual nature" for RTIL surfactants reminiscent of the solvent duality seen in condensed RTIL phases as detailed in [15].…”

Viscosity of [bmim][PF6] and [bmim][BF4] at High Pressure

“…In this study, we measured the viscosity of two ionic liquids, [bmim] [PF 6 ] and [bmim] [BF 4 ], since these ionic liquids are widely used as solvents or catalysts for many reactions such as Diels-Alder and Heck reactions. The viscosities of these ionic liquids at normal pressure were reported by several researchers [5][6][7][8][9][10][11][12][13][14] 4 ] were prepared in our laboratory following the procedures reported by other authors [15][16][17]. The product purity was confirmed by CHN elementary analysis (Table I).…”

Laser photolysis study of anthraquinone in binary mixtures ofionic liquid [bmim][PF6] and organic solvent

“…were utilized to characterize the properties of RTILs [7][8][9]. Pulse radiolysis and time-resolved fluorescence [10][11][12][13][14][15][16] have also been applied to study the reaction processes occurring in RTILs. These studies have provided some important information on the polarity and biphasic property of RTILs and have thrown light on the dynamics of ionic diffusion and internal motion of the dissolved solutes.…”