[(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