Steady-state and time-resolved fluorescence behavior of coumarin-153 in a hydrophobic ionic liquid and ionic liquid-toluene mixture

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• 作者：Sudhir Kumar Das ; Moloy Sarkar ; ^{moloysarkar@gmail.com}
• 关键词：Ionic liquid ; Time-dependent Stokes shift ; Solvation dynamics ; Nonpolar cosolvent ; Anisotropy
• 刊名：Journal of Molecular Liquids
• 出版年：2012
• 出版时间：January, 2012
• 年：2012
• 卷：165
• 期：Complete
• 页码：38-43
• 全文大小：946 K

文摘

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 ionic liquid-toluene mixtures is found to be biphasic, and the average solvation time is found to decrease with the addition of nonpolar cosolvent to the ionic liquid. A significant blue shift of the time-zero maximum of fluorescence spectrum upon addition of toluene indicates a more nonpolar environment around C-153 at the initial stage of dynamics in the mixed solvent system. A comparison of the dynamics of solvation data in ionic liquid and ionic liquid-toluene mixture suggests that toluene can effectively penetrate into the ionic liquid-rich cybotactic region of the probe. This is explained in terms of favorable hydrophobic interaction between ionic liquid and toluene.