Experimental and Theoretical Investigations of Solvation Dynamics of Ionic Fluids:  Appropriateness of Dielectric Theory and the Role of DC Conductivity

Abstract

An analysis is provided of the subnanosecond dynamic solvation of ionic liquids in particular and ionic solutions in general. It is our hypothesis that solvation relaxation in ionic fluids, in the nonglassy and nonsupercooled regimes, can be understood rather simply in terms of the dielectric spectra of the solvent. This idea is suggested by the comparison of imidazolium ionic liquids with their pure organic counterpart, butylimidazole (J. Phys. Chem. B 2004, 108, 10245-10255). It is borne out by a calculation of the solvation correlation time from frequency dependent dielectric data for the ionic liquid, ethylammonium nitrate, and for the electrolyte solution of methanol and sodium perchlorate. Very good agreement is obtained between these theoretically calculated solvation relaxation functions and those obtained from fluorescence upconversion spectroscopy. Our comparisons suggest that translational motion of ions may not be the predominant factor in short-time solvation of ionic fluids and that many tools and ideas about solvation dynamics in polar solvents can be adapted to ionic fluids.

Assessing the Roles of the Constituents of Ionic Liquids in Dynamic Solvation: Comparison of an Ionic Liquid in Micellar and Bulk Form

“…23- 25 Here we compare the micellar system formed by 1-cetyl-3-vinylimida- A typical instrument response function is shown. The decay at blue end of the spectrum decays faster than that of at the red end of the spectrum.…”

“…[33][34][35][36] Major questions regarding dynamic solvation by ionic liquids deal with whether the organic cation or the inorganic anion solvate preferentially on different time scales, the role of the correlated motion of the ion pairs and their lifetime, and the importance of translational motion of the ions relative to dipolar relaxation. [23][24][25] Here, we attempt to address some of these questions by studying the solvation of the dye, coumarin 153, in a bulk ionic liquid and its corresponding micelle in water ( Figure 1). Because coumarin 153 is only sparingly soluble and weakly fluorescent in water, a clear distinction can be made between its fluorescent properties in the bulk ionic liquid and that in the micelles formed from the ionic liquid.…”

Liquid Structure and the Ion-Ion Interactions of Ethylammonium Nitrate Ionic Liquid Studied by Large Angle X-Ray Scattering and Molecular Dynamics Simulations

“…We demonstrated a direct pH measurement in EAN by using an ion selective field effect transistor (IS-FET) electrode [22]. Moreover, dynamic properties such as a dielectric spectroscopy [23] and solvation dynamics of EAN ionic liquid [24,25] have also been reported. For further understanding of both static and dynamic properties of EAN as liquid and/or solvent, it is indispensable to elucidate the liquid structure of EAN at a molecular level.…”

Dynamic Solvation in Phosphonium Ionic Liquids: Comparison of Bulk and Micellar Systems and Considerations for the Construction of the Solvation Correlation Function, C(t)

“…35 Major questions regarding dynamic solvation by ionic liquids deal with whether the organic cation or the inorganic anion solvates preferentially on different time scales, the role of the correlated motion of the ion pairs and their lifetime, and the importance of translational motion of the ions relative to dipolar relaxation. [23][24][25] Previously, we attempted to address some of these questions by studying the solvation of the dye coumarin 153 in a bulk imidazolium ionic liquid, 1-cetyl-3-vinylimidazolium bromide ([CVIM + ][Br -]), and its corresponding micelle in water. 36 (There is a growing body of work on the subject of ionic liquids in micelles, microemulsions, and related systems.…”