Effect of Water, Methanol, and Acetonitrile on Solvent Relaxation and Rotational Relaxation of Coumarin 153 in Neat 1Hexyl3-methylimidazolium Hexafluorophosphate (original) (raw)
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The Journal of Physical Chemistry B, 2008
Molecular dynamics simulations of mixtures of 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM+][PF6-]) and water have been performed in order to investigate how small amounts of water affect the translational and rotational dynamics of this ionic liquid (IL). We find that water is closely associated with the anions and that its presence enhances both the translational and rotational dynamics of the IL. In agreement with experiments, we find that the fluorescence spectra of Coumarin-153 is red-shifted because of the presence of water. Small amounts of water enhance the speed of relaxation of the solvent surrounding the solute probe after photoexcitation, but only at a "local environment" level. Interconversion between environments still occurs on a long time scale compared with the fluorescence lifetime of the probe. Excitation wavelength-dependent emission is observed both in the neat IL and in the IL+water mixture.
Journal of Molecular Liquids, 2000
Steady-state and time-resolved fluorescence behavior of C-153 in neat ultra hydrophobic 1-(2-methoxyethyl)-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate and its mixture with toluene has been investigated. Steady-state absorption and emission spectral behavior of C-153 is found not to be affected by the nonpolar cosolvent. Time-resolved fluorescence anisotropy measurements show that the rotational diffusion of the probe becomes faster in presence of toluene. Solvation dynamics in
Journal of Molecular Liquids, 2017
Using picosecond time-correlated single photon counting (TCSPC) technique, C-153 fluorescent probe solvation and orientational dynamics in [BMIM][TFSI]/PC mixtures have been investigated. The bi-exponential fit of the solvation response gives tens and hundreds of picoseconds time-components, respectively. Both components are dependent on mixture composition. A characteristic power-law relation between integral solvation times and mixture viscosity has been extracted. As the solvation dynamics is controlled by translational motion, we chose to confront integral solvation times of C-153 in [BMIM][TFSI]/PC with the translational diffusion coefficients of BMIM + cations and propylene carbonate molecules, as well as with average rotational times , obtained measuring time-resolved fluorescence anisotropy. Our results allow to make the hypothesis that the solvation dynamics of C-153 in this mixture is mainly influenced by the cation. Highlights. Solvation responses of [BMIM][TFSI]/propylene carbonate mixtures.. Time-resolved anisotropies. A characteristic power-law relation between solvation times and mixture viscosity. The solvation dynamics of C153 is mainly influenced by the BMIM + cation entity
Chemical Physics Letters, 2010
We have investigated the micelle formation by room-temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium octyl sulfate (bmimOs) with another RTIL, ethyl ammonium nitrate (EAN). In addition, the effect of micelle formation on the solvation and rotational relaxation dynamics have been observed using steady-state and picoseconds time-resolved spectroscopy. Both the solvent and rotational relaxations of Coumarin-153 are retarded in the micelle compared to that of neat EAN. The increase in average solvation time on going from neat EAN to bmimOs-EAN micelle is very small compared to the increase in solvation time on going from pure water to water containing micelle.
Journal of Applied Solution Chemistry and Modeling, 2013
Steady state and time-resolved fluorescence behavior of coumarin153(C153) in bis(1-methyl-1H-imidazol-3ium-3-yl)dihydroborate cation containing room temperature ionic liquid and its mixture with dimethylformamide (DMF) has been investigated. Density functional calculations on the present ionic liquid have been carried out to have ground state structural information of this system. C-H N and C-H O hydrogen bonding interactions between cationic and anionic moiety of the present ionic liquid has been observed. Steady state absorption and emission spectral profiles of C153 are found not to be influenced by the polar cosolvent. Time-resolved fluorescence anisotropy experiments show that the rotational motion of the probe becomes faster in presence of DMF. During time dependent dynamic Stokes shift measurements in ionic liquid-DMF mixtures, the average solvation time is found to decrease with the addition of DMF to the ionic liquid. The decrease in both average solvation and rotational time of probe molecule upon gradual addition of polar organic co-solvent is attributed to the lowering of bulk viscosity of the medium.
Solvation dynamics of coumarin 153 in mixtures of carbon dioxide and room temperature ionic liquids
Chemical Physics Letters, 2011
Effects of dissolved carbon dioxide (CO 2 ) on the solvation dynamics of coumarin 153 were studied in 1butyl-3-methylimidazolium hexafluorophosphate, and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide by the time resolved fluorescence spectroscopy. The solvation dynamics showed an ultrafast response less than 1 ps and a slower response extended to a half of ns under ambient condition. With increasing the CO 2 pressure, the slower component became fast, although no significant change was observed for the faster component. The CO 2 effect on the average solvation time was compared with that on the translational diffusion of the solute molecule dissolved in the mixture.
Journal of Physical Chemistry B, 2007
Carbohydrates are known to serve as an abundant, diverse, and reusable source of carbon, but their derivatization for industrial applications is still a challenging task because of their low solubility in solvents other than water; they are only sparingly soluble in common organic solvents as well as in weakly coordinating ionic liquids, such as 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF 4 ). In this manuscript, we have shown that the solubility of cyclodextrins (CDs) in ethylammonium nitrate (EAN), at 298 K is comparable to that in water. This combination of EAN and γ-CD can be useful in many ways: (i) combination of both γ-CD and EAN can provide selectivity and resolution for separations that otherwise are not possible (vide infra); (ii) the combination of these two can find interesting applications in proteinÀdetergent systems (vide infra), and (iii) they can improve chiral resolutions in simultaneous enantioseparation by capillary electrophoresis method (vide infra). In this study, we have characterized this system using the following techniques: By the use of the competitive fluorescence method we have shown that there is no inclusion complex formation between EAN and γ-CD. Using the Benesi Hildebrand equation, we have shown the variation of binding constant of the C-153/γ-CD complex with temperature. The negative entropy and enthalpy changes indicated that the formation of the above C-153/γ-CD complex is entropically unfavorable and enthalpy-driven. We have also investigated the effect of temperature on the fluorescence anisotropy decays and the solvation dynamics of coumarin-153 (C-153) using picosecond time-resolved spectroscopy. Finally, we have shown that the aggregation behavior of γ-CD in EAN is entirely different from that in water, and the increase in average solvation time on going from neat EAN to EAN containing γ-CD is very small compared to the increase in solvation time on going from pure water to water containing γ-CD.
Journal of the Physical Society of Japan, 2012
The solvent effect on the steady-state and time-resolved fluorescence spectra of coumarin 120 in water was studied utilizing a molecular dynamics simulation with combined quantum mechanical/molecular mechanical method. The constructed steady-state fluorescence spectra reproduced the Stokes shift of the experimental data. The solvent effects on the spectra were examined by constructing three different spectra: spectra using the entire system, spectra including water molecules only in the first solvent shell, and spectra excluding all water molecules. We found that the variation in C-C bond length makes the largest contribution to the solvent shift in the fluorescence spectrum, which indicates the importance of the electronic structure variation.
Dynamic Solvation in Room-Temperature Ionic Liquids †
The Journal of Physical Chemistry B, 2004
The dynamic solvation of the fluorescent probe, coumarin 153, is measured in five room-temperature ionic liquids using different experimental techniques and methods of data analysis. With time-resolved stimulatedemission and time-correlated single-photon counting techniques, it is found that the solvation is comprised of an initial rapid component of ∼55 ps. In all the solvents, half or more of the solvation is completed within 100 ps. The remainder of the solvation occurs on a much longer time scale. The emission spectra of coumarin 153 are nearly superimposable at all temperatures in a given solvent unless they are obtained using the supercooled liquid, suggesting that the solvents have an essentially glassy nature. The physical origin of the two components is discussed in terms of the polarizability of the organic cation for the faster one and the relative diffusional motion of the cations and the anions for the slower one. A comparison of the solvation response functions obtained from single-wavelength and from spectral-reconstruction measurements is provided. Preliminary fluorescence-upconversion measurements are presented against which the appropriateness of the single-wavelength method for constructing solvation correlation functions and the use of stimulated-emission measurements is considered. These measurements are consistent with the trends mentioned above, but a comparison indicates that the presence of one or more excited states distorts the stimulated-emission kinetics such that they do not perfectly reproduce the spontaneous emission data. Fluorescence-upconversion results indicate an initial solvation component on the order of ∼7 ps. †