スライド 1

Charge Transfer Reaction and
Solvation Dynamics in Ionic Liquid
Satoe MORISHIMA
MIYASAKA laboratory
Contents
Introduction
✦ What is ionic liquid?
My project
✦ Sample , charge transfer reaction
✦ Solvation
✦ Time-resolved Fluorescence
✦ Result and Discussion
✦ Recent work
What is Ionic liquid ?
Ionic liquid is・・・
1-ethyl-3-methylimidazolium
（emim+）
1-butyl-3-methylpyridinium
Melted salt at room temperature
Constructed from organic cation and anion
trihexyl(tetradecyl)phosphonium
NaCl
N,N-Diethyl-N-methyl-N-(methoxyethyl)
ammonium
DEME BF4
bis(trifluoromethylsulfonyl)imide
（TFSI-）
tetrafluoroborate
m.p / ℃
NaCl
800
DEME BF4
9
emim TFSI
-16
Ionic liquids Application
•Electric conductivity
•Vapor pressure
nearly 0
Biochemistry
Energy device
• Hard to burn
•High viscosity
material
Bioreactor
a fuel cell
actuator
Heat-resist gel
•Heat-resist
・・・etc
Green chemistry
Solvent for synthesis
refining
Background
Synthesized in1992 by J.S.Wilkes and M.J.Zawarotko
Measurement of Solvation dynamics in 2002 by Karmakar. R and Samanta. A
rotation
diffusion
ｈn
ｈn
: dipole
??
Sergei Arzhantsev, Huii jin, Gray A. Baker, and Mark Maroncelli J. Phys. Chem. B 2007, 111, 4978-4989
About
My project
charge transfer reaction
BA
CT
9,9’-bianthryl
reaction
Locally excited :
LE
electrically
symmetric
Charge transfer : CT
ADMA
electrically
asymmetric
4-(9-anthryl)-N,N’dimethylaniline
C153
coumarin153
δ+
δ-
reference dye
Background ＆ Motivation
CT state
LE state
cyclohexane
DEME BF4
hν
ground state
solvent
viscosity / cP
DEME BF4
1200
cyclohexane
0.375
ethanol
0.44
cP: g / cm・s
Time-resolved Fluorescence
- principle Time-resolved spectroscopy
time
energy
Excited state
hn
time
Red shift
Directly observation of
Solvation Dynamics !
Ground state
time
Solvation coordinate
Time-resolved Fluorescence
- Time-correlated single photon counting (TCSPC) Laser pulse
Counts
t’
t
photon
125 ns
time
Light source: Ti: Sapphire laser
Exciting λ: absorption peak
（second harmonic Ti: Sapphire laser ）
System response time： ~36 ps （FWHM）
Step size: 4 ps
temperature： 295K
Result
(1)
Decay
time
(2)
Rise
(1)
(2)
LE to CT reaction
already finished !
Result ＆ Discussion
64 %
25 %
65 %
The image of Solvation in ionic liquid
Normalized (10 ps ~30 ns)
Recent work
23x10
3
(1) fs transient Absorption
(2) TCSPC under row temperature condition
21
Fitting with multi-exponential function
20
19
Why rise ?
18
10
10
Intensity
Peak Shift / cm
-1
22
17
10
1
10
2
10
3
Time / ps
10
4
10
10
10
4
3
2
1
0
0
20
40
Time / ps
60
80x10
3
Summary
The degree of solvent orientation at ground state makes for the ultra-fast
solvation dynamics after excitation
In the range of 10 ps~30 ns, the solvation time of ADMA is not so different
from that of BA.
Result suggested that initial solvent orientation in the
ground state strongly affects the ultra-fast portion of the
solvation process (<25 ps).
Fin.
Transient Absorption (TA)
(1)
I0
(2)
I
Sn
monitor pulse
pump pulse (λ: const.)
monitor pulse
detector
S1
pump pulse
⊿t
S0
(1)
(2)
Viscosity and Ion size
Stokes-Einstein equation
D =kBT / 6πηR
Application to synthesis
Huvddleston,J.G, Willauer,H.D., Swayloski, R.P., Vsser,A.E., Rogers,R.D., Chem.Commun., 1998, 1765-1766
Application to refining 1
Application to refining 2
C.Lee et al., J.Chem.Research (s), 122 (2002)
Application to energy device
anode
cathode
H2
O2
H2O
H2 O
anode
cathode
H2
Imidazole
O2
H2O
λ 
Iλ
I peak

Intpeak
Intλ
Il： Intensity at observation λ
Intl： Integration at observation λ
Ipeak： Intensity at peak λ
Intpeak： Integration at peak λ
22
Dynamics Stokes shift
Fitting with
log-normal Function
→Fluo.Max / cm-1
2


 







0
ln
1

2
b
 


  



  

I  I 0 exp ln(2)

 
b


 


 
I0 : ピーク強度 b : 非対称パラメータ
νp : ピーク波数
Δ : スペクトルパラメータ
23
Solvation time
Correlation function
C t  
Multi-exponential function
n t  n  
n 0 n  
f (t )   Ai exp(t /τi )
i
n (t)：peak wavenumber at Time=t
Ai : Intensity
n (0)： peak wavenumber at Time=0
τi : life time
溶媒和応答関数解析結果
n (∞)：peak wavenumber at Time=∞
Observed Solvation Times Derived from the time dependent Stokes Shift of CT
Life time / ps
BA
ADMA
C153
τ1
68 ± 5
89 ± 4
48 ± 3
τ2
610± 31
548 ± 28
441 ± 24
τ3
3884 ± 94
2561 ± 70
2335 ± 77
Av. solvation Time
1238
1052
986
24
Potential energy
interaction
Energy dependence of r
Average of energy
/ (kJ mol-1)
ion - ion
1/r
250
ion - dipole
1 / r2
15
dipole – dipole
(not move)
1 / r3
2
dipole – dipole
(rotate)
1 / r6
0.6
London force
1 / r6
2
アトキンス物理化学(下) 第６版２２章ｐ７１６

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