eisuke takeuchi miyasaka lab. photoinduced electron transfer in bianthryl and derivatives in ionic...
TRANSCRIPT
Eisuke Takeuchi Miyasaka Lab.
Photoinduced Electron Transfer in Bianthryl and derivatives in Ionic Liquid
Contents
I. IntroductionWhat is ionic liquid (IL)?Charge transfer (CT) of bianthryl derivatives.
II. MotivationEffect of pre-solvation on CT dynamics.
III.Experimental methodFemtosecond transient absorption (TA) spectroscopy.
IV. My workComparison of symmetric and asymmetric bianthryl derivatives.
V. Summary
What is ionic liquid (IL)?
Ionic Liquid Inorganic salt
ex. NaClDeme BF4
CH3
NC2H5 C2H4OCH3
C2H5
F
B
F F
F
m.p 9℃ m.p 800℃
N NH3C C4H9
NS S
F3C CF3
O
O O
O
Bmim TFSI m.p -4℃
Ionic Liquid : Molten organic salt at room temperature, which consists of organic cations and inorganic anions
Science 302, 792 (2003)
S. Kuwabata, et al., Chem. Lett. 35, 600 (2006)
SEM image of IL.IL does not vaporize even in vacuum.
What is ionic liquid (IL)?
Electric conductivityVapor pressure: nearly 0Hard to burn (fire resistant)Heat-resistantHigh viscosity etc…
Application in various fields.Safe and sustainable solvent
( Green solvent )Electrochemical
device ( Electrolyte )Lubricant
Organic solventIonic Liquid
hυ
: cation: anion
CH3CN
hυ
δ+ δ-
Solvation Dynamics (溶媒和ダイナミクス)
Charge transfer (CT) of bianthryl derivatives
hυ
Locally Excited (LE) state Charge Transfer (CT) state9,9’-Bianthryl (BA)
*
LE emission
CN
10-Cyano-9,9’-Bianthryl (CNBA)
Solute of this experiment
Electron withdrawing group
According to quantum chemical calculationslowering CT state 0.25eV in comparison with BA
M. Jurczok et al. Chemical Physics. . 256, (2000) 137-
LE state
hυCT emission
CT state
ener
gy
solvation coordinate
CNBA
Charge transfer (CT) of bianthryl derivatives
BA
0.25eV
MotivationPeculiarity of solvation coordinate and dynamics effect reactivity of solute
CN
polar molecule nonpolar molecule with a symmetric
Pre - solvation different ?
: cation: anion
Femtosecond transient absorption (TA) spectroscopyTransient Absorption ( 過渡吸収 )
D t
SampleDetector
delay time
pulse2
pulse1
delay time D t : several fs ~
1 fs = 10-15 s = 0.000 000 000 000 001 seconds
distance that light travels in1s 30 fs
globe7.5 times( 300,000 km )
pylori bacteria3 times( 9 μm )
pulse-duration : 30 fs
CN * CN
+
-
My work
Delay tim
e
Time constant: 0.063ps
672nm
My work
Delay tim
e-
+
CN
δ-
δ+
CN
720nm
Time constant : 60ps
Compare BA
BA
680nm
Time constant CNBA : 0.063ps BA : 1.25ps
Time constant : 60ps
Time constant: 0.063ps
hυ
*
δ-
δ+
-
+
My work
CN
CN
CN
CN
LE state
Grand state
CT state
Solvation (1.5ns)
Summary
Charge transfer in CNBA / Deme BF4 is more faster than charge transfer by solvation and unaffected by solvation
The ultrafast CT kinetics could be arising from the pre-solvation state caused by the polar nature of asymmetric CNBA, while for nonpolar symmetric BA, much drastic solvent reorganization is required.
LE stateCT state
LE state
CT state
CNBABA
0.5 kcal / mol
K. Tominaga et al. J. Phys. Chem. 95, 10485 (1991)
≈ 0