Observations of probe dependence of the solvation dynamics in ionic liquids

Abstract

Solvation and rotational dynamics of 4-aminophthalimide (4AP) in four ionic liquids (ILs) are measured using a combination of fluorescence upconversion spectroscopy and time-correlated single photon counting. These data are compared with previously reported data for coumarin 153 (C153) to investigate the probe dependence of solvation dynamics. No fast component (<15 ps) in the fluorescence anisotropy is observed with 4AP. The differences between the solvation response functions of 4AP and C153 are significant in all four ILs, but these differences can be reduced by applying a correction for solute rotation using measured emission anisotropies. Response functions of other probes available in the literature are used to further examine the validity of this correction. The corrected data are also compared to predictions of dielectric continuum models of solvation. By replacing the measured static conductivity of the ILs with an estimated value, such predictions show good agreement with the observed spectral response functions, especially when the anion size is small.

Solvation dynamics: improved reproduction of the time-dependent Stokes shift with polarizable empirical force field chromophore models

“…C153 is a commonly used fluorophore, which increases its dipole moment upon excitation. 2,14,22,[34][35][36][37][38] In contrast, MQ lowers its dipole moment upon excitation, which makes it an interesting test case, and has gained increasing interest due to its small size and rigid structure. 14,19,20,[39][40][41] As solvents, methanol (MeOH) and the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EmimOTf) were chosen.…”

“…Upon excitation, both the dipole moment and the polarizability of the chromophore change, so that both the electrostatic and dispersion interactions change. 21 In recent years, the increasing accuracy and resolution of experiments facilitated the detailed analysis of even very small effects on the TDSS, such as the probe dependence of the obtained timescale, 14,22 or the change in the TDSS upon addition of a side chain to a chromophore. 23 To account for such small effects in computer simulation more accurate solvent and chromophore models are needed.…”

Equilibrium Solvation, Electron-Transfer Reactions, and Stokes-Shift Dynamics in Ionic Liquids

“…Despite the fact that conductivity is a part of the frequency-dependent dielectric function, dielectric theories of solvation fail to capture the longtime solvation dynamics, predicting dynamics too fast compared to experiment. 13,14 This study develops a microscopic model of the dynamic susceptibility of ionic liquids to calculate the electrostatic response to altering charge distribution of the solute. The formalism combines the inverted-space charge−charge structure factors supplied by molecular dynamics (MD) simulations with dynamic memory function incorporating the experimental dielectric function.…”

Dissolution of Trihexyltetradecylphosphonium Chloride in Supercritical CO2

“…In this paper, we present a more complete spectroscopic study of the [P6, 6,6,14] + Cl − /scCO2 system. Specifically, we report on the steady-state and time-resolved spectroscopy of C153 as a reporter of [P6, 6,6,14] + Cl − dissolution in scCO2 at 323 K. C153 was chosen for these studies because it has a rich history of use as a probe of solvation and solvation dynamics in liquids and supercritical fluids [22,24,[48][49][50], and represents a nearly ideal probe of solvation. The photophysics are simple and the S0 → S1 transition is not complicated by any nearby transitions [51,52].…”