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 .
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.