Effect of water, methanol, and acetonitrile on solvent relaxation and rotational relaxation of coumarin 153 in neat 1-hexyl-3-methylimidazolium hexafluorophosphate

被引:115
作者
Chakrabarty, D [1 ]
Chakraborty, A [1 ]
Seth, D [1 ]
Sarkar, N [1 ]
机构
[1] Indian Inst Technol, Dept Chem, Kharagpur 721302, W Bengal, India
关键词
D O I
10.1021/jp0460339
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
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][PF6]) 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][PF6] 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.
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收藏
页码:1764 / 1769
页数:6
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