Steady-state and time-resolved fluorescence behavior of coumarin-153 in a hydrophobic ionic liquid and ionic liquid–toluene mixture (original) (raw)
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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
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.
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.
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.
Dual Fluorescence and Solvatochromic Study on 3-Acyl Coumarins
Journal of Fluorescence, 2017
Electronic absorption and emission spectra of 3acetyl coumarin, 3-(bromoacetyl) coumarin and 3-(di bromoacetyl) coumarin have been recorded at room temperature in thirteen solvents with different polarities. Both ground and excited state dipole moments have been calculated for both locally excited and charge transfer transitions by using the solvatochromic method. Excited state dipole moments of all the three compounds are higher than their ground state values. DFT calculations have been profound to estimate their ground and excited state dipole moments. The estimated change in dipole moment by the application of microscopic solvent polarity parameter and bulk solvent polarity methods are in close agreement. Concentration dependent dual fluorescence has been observed in the emission spectra of all the three compounds.
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 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.
Luminescence : the journal of biological and chemical luminescence, 2017
The UV/Vis absorption and fluorescence characteristics of 3-cyano-7-hydroxycoumarin [CHC] and 7-amino-4-methyl-3-coumarinylacetic acid [AMCA-H] were studied at room temperature in several neat solvents and binary solvent mixtures of 1,4-dioxane/acetonitrile. The effects of solvent on the spectral properties are analyzed using single and multi-parameter solvent polarity scales. Both general solute/solvent interactions and hydrogen bond interactions are operative in these systems. The solvation of CHC and AMCA-H dyes in 1,4-dioxane/acetonitrile solvent mixtures has been studied. The solutes CHC and AMCA-H are preferentially solvated by acetonitrile and a synergistic effect is observed for both molecules in dioxane/acetonitrile solvent mixtures. In addition, using the solvatochromic method the ground- and the excited-state dipole moments of both the dyes were calculated. The ground- and excited-state dipole moments, absorption and emission maxima and HOMO-LUMO gap were also estimated t...
Journal of Physical Chemistry A, 2005
The dynamics of solvent relaxation in ionic liquid (IL)-water, IL-methanol, and IL-acetonitrile mixtures have been investigated using steady state and picosecond time-resolved fluorescence spectroscopy. We have used Coumarin 153 (C-153) and 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF 6 ]) as fluorescence probe and IL, respectively. The steady-state emission spectra showed that the gradual addition of cosolvents increases the polarity of the mixtures. In neat [hmim] [PF 6 ] and all IL-cosolvent mixtures, solvation occurs in two well-separated time regimes within the time resolution of our instrument. A substantial portion of the solvation has been missed due to the limited time resolution of our instrument. The gradual addition of cosolvents decreases the viscosity of the medium and consequently solvation time also decreases. The decrease in solvation time is more pronounced on addition of acetonitrile compared to water and methanol. The rotational relaxation time of the probe is also decreasing with gradual addition of the cosolvents. The decrease in viscosity of the solution is responsible for the decrease in the rotational relaxation time of the probe molecule.