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[(CF3SO2)2N]-
BF
F FF
NR
NN R
R
Charge Transfer Reaction and Solvation Dynamics in Ionic
Liquid
Satoe MORISHIMAMIYASAKA 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 ?
trihexyl(tetradecyl)phosphonium
N NCH3CH2
N
NS S CF3
O
OF3C
O
O
PC6H13C6H13
C6H13 C14H29
BF
F FF
NCH3CH3
CH3 CH2CH2OCH3
tetrafluoroborate
DEME BF4
1-ethyl-3-methylimidazolium( emim+ )
bis(trifluoromethylsulfonyl)imide( TFSI- )
1-butyl-3-methylpyridinium N,N-Diethyl-N-methyl-N-(methoxyethyl) ammonium
Ionic liquid is ・・・ Melted salt at room temperature
Constructed from organic cation and anion
NaCl
m.p / ℃
NaCl 800
DEME BF4 9
emim TFSI
-16
Ionic liquids Application
a fuel cellactuator
Bioreactor
Heat-resist gel
Green chemistry
Biochemistry
Energy device
material
Solvent for synthesis
refining
•Electric conductivity
•Vapor pressure
nearly 0
• Hard to burn
•High viscosity
•Heat-resist
・・・ etc
Background
Measurement of Solvation dynamics in 2002 by Karmakar. R and Samanta. A
Synthesized in1992 by J.S.Wilkes and M.J.Zawarotko
Sergei Arzhantsev, Huii jin, Gray A. Baker, and Mark Maroncelli J. Phys. Chem. B 2007, 111, 4978-4989
??
: dipole
rotation diffusion
h h
AboutMy project
electricallysymmetric BA
9,9’-bianthryl
ADMA4-(9-anthryl)-N,N’-
dimethylaniline
C153coumarin153
Locally excited : LE Charge transfer : CT
electricallyasymmetric
NCH3CH3
N O O
CF3
δ+
δ-N O O
CF3
NCH3CH3
CT
reaction
reference dye
charge transfer reaction
Background & Motivation
NCH3CH3
NCH3CH3
solvent viscosity / cP
DEME BF4 1200
cyclohexane 0.375
ethanol 0.44
LE state
CT state
hν
ground state
cyclohexane DEME BF4
cP: g / cm ・ s
Directly observation of
Solvation Dynamics !
Excited state
h
Ground state
Solvation coordinate
ener
gy
Time-resolved spectroscopy
Red shift
time
Time-resolved Fluorescence - principle -
time
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
t t’
photon
Laser pulse
125 ns time
Co
un
ts
Time-resolved Fluorescence - Time-correlated single photon counting (TCSPC) -
Result
Rise
Decay
time
(1) (2)
(1)
(2)
LE to CT reaction already finished !
The image of Solvation in ionic liquid
Result & Discussion
65 %25 %64 %
Normalized (10 ps ~30 ns)
100
101
102
103
104
Inte
nsity
80x103
6040200
Time / ps
Recent work23x10
3
22
21
20
19
18
17
Pea
k S
hift
/ c
m-1
101
102
103
104
Time / ps
(1) fs transient Absorption
(2) TCSPC under row temperature condition
Fitting with multi-exponential function
Why rise ?
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.
I0 I
pump pulse (λ: const.)
monitor pulse
⊿t
detector pump pulse
monitor pulse
S0
Sn
S1
(1)
(2)
(1) (2)
Transient Absorption (TA)
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
N NCH3CH2
CH3F3C S
O
O
O
F3C S
O
O
OH H F3C S
O
O
O
Application to refining 1
Application to refining 2
C.Lee et al., J.Chem.Research (s), 122 (2002)
catho
de
ano
de
OH
HOH
HOH
HOH
HH
catho
de
ano
deN N HH
N N H N NH
H2O
Imidazole
H2
H2
O2
H2O
O2
H2O
Application to energy device
22
λ
peak
peak
λλ Int
Int
I
I
Il : Intensity at observation λ
Intl : Integration at observation λ
Ipeak : Intensity at peak λ
Intpeak : Integration at peak λ
23
Fitting with
log-normal Function
→Fluo.Max / cm-1
2
0
0
21ln)2ln(exp
b
bII
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
Dynamics Stokes shift
24
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
溶媒和応答関数解析結果(t) : peak wavenumber at Time=t
(0) : peak wavenumber at Time=0
(∞) : peak wavenumber at Time=∞
0
ttC
Correlation function
Multi-exponential function
i
ii tAtf )/exp()( τ
Ai : Intensity
τi : life time
Observed Solvation Times Derived from the time dependent Stokes Shift of CT
Solvation time
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
Potential energy