Ultrafast Solvation Dynamics of Coumarin 153 in Imidazolium- Based Ionic Liquids Barnhard Lang,...
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![Page 1: Ultrafast Solvation Dynamics of Coumarin 153 in Imidazolium- Based Ionic Liquids Barnhard Lang, Gonzalo Angulo, and Eric Vauthey J.Phys.Chem.A 2006, 110.](https://reader035.fdocuments.net/reader035/viewer/2022081513/56649f055503460f94c19dec/html5/thumbnails/1.jpg)
Ultrafast Solvation Dynamics of Coumarin 153 in Imidazolium-Based Ionic Liquids
Barnhard Lang, Gonzalo Angulo, and Eric VautheyJ.Phys.Chem.A 2006, 110. 7028-7034
Miyasaka Lab.
Masayasu Muramatsu
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Contents
Introduction• Room-Temperature Ionic Liquids• Solvation dynamics
Experimental• Fluorescence up-conversion• Three-pulse photon-echo peak-shift
Results & discussion
Summary
N+
N
N
N-
S S
O
OO
O F
F
F
F
F
F
[cnpmim]+
[Tf2N]-
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Room-Temperature Ionic Liquids
Room-temperature ionic liquids (RTILs) are organic molten salts
Ultralow volatility: 揮発性
Flameproof
Electrochemical stability
High viscosity
http://www.chem.eng.osaka-u.ac.jp/~elechem/Research.htm http://www.tuat.ac.jp/~ohno/lab/ionic_liquid/IL.html
Application for the Electron Microscope
Star sand SEM imageIonic liquidleft:with RTIL right:bulk
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Solvation dynamics
hν
Solvation in conventional liquids
Ener
gy
Solvation Coordinate
S0
S1
hν
Stabilization
Exited state
Ground state
strongly solvated
通常の有機溶媒
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Solvation dynamics
○:anion●:cation
Solvation in ionic liquidsDynamic Stokes-shift
Ener
gy
Solvation Coordinate
S0
S1
Solvation
hνemission
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Fluorescence up-conversion
Intensity
time
time
time
delay
Excitation pulse : ωe
Fluorescence : ωf
Gate pulse : ωg
Sum frequency : ωs= ωf+ ωg
0
0
0
sample
BBO
ωe
ωf
ωg
ωs
delay
mono
chr.PMT
ω s = ω f+ω gExitationGate
BBO:β-BaB2O4
monochr: モノクロメーター(分光器) PMT: 光電子増倍管
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Three-pulse photon-echo peak-shiftpeak-shift τ’
―:-k1+k2+k3
―: k1-k2+k3
T → large
τ’ → small
3PEPS resultsτ’ vs T
pulse1 makes the coherence of polarization.pulse2 interferes with pulse1 indeced polarization.pulse3 is diffracted as the signal.
τ=0 : Transient Grating → no echo
τ 0≫ : decoherent → no echo
T 0≫ : vanish diffraction fringe → no echo干渉縞
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Fluorescence up-conversion
Coumarin153 in[cnpmim+][Tf2N-] and[pmim+][BF4
-]
Excitation : 400nmResponse function : 230fs
Dynamic red shift
N+
N
N+
N
N N-
S S
O
OO
O F
F
F
F
F
F
BF4-
[pmim]+
[cnpmim]+ [Tf2N]-
Red : rise Blue : decay
Steady-state absorption and emission spectra
Fluorescence time profiles
× :490nm▼ :540nm● :580nm
× :490nm▼ :540nm● :580nm
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Fluorescence up-conversion
Dynamic red shift
Too small peak shift change → ultrafast component?
4600cm-1
600cm-1
500cm-1
Reconstructed time-dependent emission spectra
Time dependence of the emission band maximum
Missing red shift
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Three-pulse photon-echo peak-shift
Indocyanine green in[cnpmim+][Tf2N-] and ethanol
Excitation : 800nmPulse duration : 15fs
Differ from Stokes-shift measurements
Inertial part: Signal starts at a higher level and decays slower in ionic liquids
in ionic liquid
in ehtanol
molecular vibration
inertial part
3PEPS results
溶媒の平均自由行程内
分子振動
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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.