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Ultrafast Solvation Dynamics of Coumarin 153 in Imidazolium-Based Ionic Liquids

Barnhard Lang, Gonzalo Angulo, and Eric Vauthey J.Phys.Chem.A 2006, 110. 7028-7034. Ultrafast Solvation Dynamics of Coumarin 153 in Imidazolium-Based Ionic Liquids. Miyasaka Lab. Masayasu Muramatsu. Contents. Introduction Room-Temperature Ionic Liquids Solvation dynamics Experimental

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Ultrafast Solvation Dynamics of Coumarin 153 in Imidazolium-Based Ionic Liquids

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  1. Barnhard Lang, Gonzalo Angulo, and Eric Vauthey J.Phys.Chem.A 2006, 110. 7028-7034 Ultrafast Solvation Dynamics of Coumarin 153 in Imidazolium-Based Ionic Liquids Miyasaka Lab. Masayasu Muramatsu

  2. Contents • Introduction • Room-Temperature Ionic Liquids • Solvation dynamics • Experimental • Fluorescence up-conversion • Three-pulse photon-echo peak-shift • Results & discussion • Summary [cnpmim]+ [Tf2N]-

  3. Room-Temperature Ionic Liquids Room-temperature ionic liquids (RTILs) are organic molten salts • Ultralow volatility:揮発性 • Flameproof • Electrochemical stability • High viscosity Application for the Electron Microscope Ionic liquid Star sand SEM image left:with RTIL right:bulk http://www.tuat.ac.jp/~ohno/lab/ionic_liquid/IL.html http://www.chem.eng.osaka-u.ac.jp/~elechem/Research.htm

  4. Solvation dynamics Exited state Stabilization hν Ground state hν strongly solvated Solvation in conventional liquids 通常の有機溶媒

  5. Solvation dynamics Dynamic Stokes-shift Solvation hν emission Solvation in ionic liquids ○:anion ●:cation

  6. Fluorescence up-conversion Excitation pulse : ωe Intensity Fluorescence : ωf delay ωs time ωf 0 Gate pulse : ωg PMT mono chr. BBO delay ωe ωg sample time 0 ωｓ= ωｆ＋ωｇ Exitation Sum frequency : ωs= ωf+ ωg Gate 0 time BBO:β-BaB2O4 monochr:モノクロメーター（分光器） PMT:光電子増倍管

  7. Three-pulse photon-echo peak-shift pulse1 makes the coherence of polarization. pulse2 interferes with pulse1 indeced polarization. pulse3 is diffracted as the signal. peak-shiftτ’ ―:-k1+k2+k3 ―: k1-k2+k3 T→large τ’→small τ=0：Transient Grating →no echo τ≫0：decoherent→no echo T≫0：vanish diffraction fringe→no echo 3PEPS results τ’vsT 干渉縞

  8. Fluorescence up-conversion [pmim]+ [cnpmim]+ [Tf2N]- Coumarin153 in[cnpmim+][Tf2N-] and[pmim+][BF4-] Steady-state absorption and emission spectra Excitation : 400nm Response function : 230fs Dynamic red shift • Red : rise • Blue : decay Fluorescence time profiles

  9. Fluorescence up-conversion 4600cm-1 600cm-1 500cm-1 Dynamic red shift Missing red shift Reconstructed time-dependent emission spectra Too small peak shift change →ultrafast component? Time dependence of the emission band maximum

  10. Three-pulse photon-echo peak-shift in ionic liquid molecular vibration 分子振動 inertial part 溶媒の平均自由行程内 in ehtanol 3PEPS results Indocyanine green in[cnpmim+][Tf2N-] and ethanol Excitation : 800nm Pulse duration : 15fs Differ from Stokes-shift measurements Inertial part:Signal starts at a higher level and decays slower in ionic liquids

  11. Summary The dynamic Stokes shift of coumarin 153 in Room temperature ionic liquids(RTILs) has been measured using fluorescence up-conversion techniques with a response function of 230fs. Three-pulse photon-echo peak-shift(3PEPS) experiments on indocyanine green in RTILs has been measured. Ultrafast solvation in RTILs which could not be observed by fluorescence up-conversion was suggested from 3PEPS results. Improved 3PEPS may find farther information.

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