1

陳順基明志科技大學化工系

The Exciplex Formation of Charge-Transfer Induced 4- Phenylbenzophenone with Triethylamine and the Application in

Photochemistry

4- 苯基二苯甲酮與三乙胺電荷 - 轉移誘導激態複合體的形成及其光化學的應用

中華民國一百年十二月二十四日

Jablonski Diagram

2

螢光吸收

S0

S1

T1

磷光外轉換

系統間穿越

振動弛緩

振動弛緩

激發單重態(Sn) 激發三重態(Tn)

內轉換或

S2

內轉換

Photophysics

Photochemistry

Identification of (n, *) & (, *)

3

單態的（ n , * ）及（ , * ）性質：

參態的（ n , * ）及（ , * ）性質：

3(n , *)3( , *)

磷光生命期 < 10-1～ 10-2 sec > 1 sec

磷光振動結構 恆定 可變

EST< 36 kJ/mol （酮類

） > 60 kJ/mol

S0T1 躍遷強度 f ~ 10-510-7 f ~ 10-11 （烴類）

重原子效應對 S0

T1 躍遷強度影響 影響小 強度增大

ESR 信號 無 有

1(n , *)1( , *)

吸收強度 弱 強溶劑效應 藍移 紅移

躍遷的極性 重直於分子面 平行於分子面

能量 通常為最低能量躍遷（共軛系統中有例外）

4

Molecular Complex

Electron donor-acceptor complex (EDA complex)

Mulliken CT 吸收理論

Ψ(S0) = aΨ(DA) + bΨ(D+A-)

Ψ(S1) = aΨ (D+A-) bΨ (DA)

ECT = ID EA (H1 H0)

hv(A D)..... .....D+)*(A-

.....D)(A + hv'

A- + D+

基態分子複合體 電荷轉移 激發態 光化學反應產物

S1

S0

ECT

ID

EA

D+ + A

-

D + A

H1

H0

D A 間距離

E

5

激態雙體 (Excimer, Excited dimer)

(Forster et al Z. Phys. Chem. 1954)

6

激態複合體 (exciplex, excited complex)

+

perylene

NCH3

CH3

N,N-dimethylaniline

*

NCH3

CH3

*

nonpolar solvent

polarsolvent

NCH3

CH3+

exciplex

(Leonhardt et al Ber. Bunsenges. Phys. Chem. 1963)

7

Photophysics of BP & PBP

200 300 400 500 600 700

0.0

0.2

0.4

0.6

0.8

1.0

0.0

0.2

0.4

0.6

0.8

1.0

Rel

ativ

e In

tens

ity

BP/EPA at 77K PBP/EPA at 77 K BP/benzene at 298 K PBP/benzene at 298 K

Abs

orba

nce

Wavelength(nm)

1/500

1/200

BP及 PBP 吸收及溶劑效應

化合物名稱四氯化碳

(nm) 苯 苯 (nm) (M-1cm-1)

EPA(nm)

氰甲烷(nm)

BP 350 347 120 344 340

PBP ~ 350 ~ 350 320 ~ 347 ~ 347

O O

Benzophenone (BP) 4-Phenylbenzophenone (PBP)

8

Vibrational structure

Vibrational structure provides clues as to which transitions are most possible

vC=O

O *

vC=O

O

*

vC=C

vC=C

400 450 500 550 600 650 700

0.0

0.2

0.4

0.6

0.8

1.0

Y A

xis

Titl

e

X Axis Title

400 450 500 550 600 650 700

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

Y A

xis

Titl

e

X Axis Title

300 350 400-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

Re

lativ

e In

ten

sity

Wavelength(nm)

Emission of biphenyl

vC=C

9

Lifetimes & Quantum yields BP及 PBP在 EPA 中的低溫磷

光生命期Monitored at p R2

BP（ 413 nm ） 5.26 ms 0.9990

BP（ 444 nm ） 5.28 ms 0.9993

BP（ 476 nm ） 5.29 ms 0.9988

PBP（ 469 nm ） 259.6 ms 0.9987

PBP（ 499 nm ） 259.6 ms 0.9989

0 10 20 30 40 50

0

10

20

30

0 10 20 30 40 50

0

10

20

30

40

0 10 20 30 40 50

0

10

20

30

(c) monitored at 476 nm

Data: bplifetime476_BModel: ExpDec1 Equation: y = A1*exp(-x/t1) + y0 Weighting:y No weighting Chi^2/DoF = 0.03087R^2 = 0.99875 y0 0.06513 ? .01081A1 24.25385 ? .05062t1 5.28542 ? .01823

Inte

nsi

ty

Time (ms)

(b) monitored at 444 nm Data: bplifetime444_DModel: ExpDec1 Equation: y = A1*exp(-x/t1) + y0 Weighting:y No weighting Chi^2/DoF = 0.03728R^2 = 0.99929 y0 0.03928 ? .01187A1 35.34288 ? .05568t1 5.27718 ? .01373

Inte

nsi

ty

(a) monitored at 413 nm Data: bplifetime413_FModel: ExpDec1 Equation: y = A1*exp(-x/t1) + y0 Weighting:y No weighting Chi^2/DoF = 0.02944R^2 = 0.99903 y0 0.04116 ? .01054A1 26.88735 ? .04955t1 5.26019 ? .016

Inte

nsi

ty0 200 400 600 800 1000

0

10

20

30

40

50

60

70

0 200 400 600 800 1000

0

10

20

30

40

50

60

70

(b) monitored at 499 nmData: PBP499nm_BModel: ExpDec1 Equation: y = A1*exp(-x/t1) + y0 Weighting:y No weighting Chi^2/DoF = 0.27758R^2 = 0.99888 y0 -0.74411 ? .0445A1 63.17799 ? .07037t1 259.63487 ? .74582

Intensity

Time (ms)

(a) monitored at 469 nmData: PBP469nm_BModel: ExpDec1 Equation: y = A1*exp(-x/t1) + y0 Weighting:y No weighting Chi^2/DoF = 0.31267R^2 = 0.99875 y0 -2.22877 ? .04671A1 61.94787 ? .07179t1 259.59948 ? .78394

Intensity

BP及 PBP 螢、磷光相對量子產率

化合物名稱298 K 77 K

f p f p

BP ~ 0 1.510-3 ~ 0 0.72

PBP ~ 0 9.510-4 ~ 0 0.46

10

State energy diagram

50

60

70

100

110

80

kcal/mol

S1(n , )

S2( , )

T1(n , ) T2( , )

S2( , )

S1(n , )

T1( , )

T2(n , )

Phenyl-substitutent can stabilize the (, *) energy levels.

O O

Benzophenone (BP) 4-Phenylbenzophenone (PBP)

11

Phosphorescence Quenching of BP

TEA 的濃度（M ）

磷光強度比值（ o/ ）

BP 的磷光生命期 a

（ s ）

0 1.00 6.75

2x10-5 1.09 5.52

4x10-5 1.34 4.42

1x10-4 2.17 2.39

2x10-4 3.20 1.47

5x10-4 5.95 0.796

a. Monitored at 450nm

400 450 500 550 600 650

0.0

0.1

0.2

0.3

0.4

0.5

Wavel engt h( nm)

0 M TEA

2*10-5M TEA

4*10-5M TEA

1*10-4M TEA

2*10-4M TEA

5*10-4M TEA

Re

lat

iv

e

In

te

ns

it

y

BP = 5*10 -3 M

12

Stern-Volmer Analysis

Quenching rate constant

kq a（ M-1s-1 ） 1.5×109

kq b（ M-1s-1 ） 2.2×109

kq c（ M-1s-1 ） 2×109

a： steady-stateb： transient lifetimec： Fouassier J. Chim Phys. 1983

0 1 2 3 4 5

0

20

40

60

80

100

120

0 1 2 3 4 5

1

2

3

4

5

6

r=0.9956

(b)

(τobs

-1-τ

0

-1)*10

-4

[TEA] *104 (M)

r=0.9977

(a)

Φ0/Φ

13

400 450 500 550 600 650 700

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Rel

ativ

e In

tens

ity

Ex=350 nm

0M TEA

1*10-5M TEA

2.5*10-5M TEA

5*10-5M TEA nondegas

Wavelength(nm)

300 320 340 360 380 400 420 440

0.6

0.7

0.8

0.9

1.0

1.1

1.2

Rel

ativ

e In

tens

ity

Wavelength(nm)

Em = 480 nm Em = 650 nm

Excitation spectra

Phosphorescence Quenching of PBP

14

Solvent Effect of PBP-TEA Exciplex

600 625 650 675 7000.0

0.2

0.4

0.6

0.8

1.0 benzene ( = 2.28)

ether ( = 4.30)

ethyl acetate ( = 6.02)

Rel

ativ

e In

tens

ity

Wavelength (nm)

polor solvent

SSIP

-A

+D .......

exciplex

[DA]*

15

Stern-Volmer Plot

TEA 的濃度（M ）

PBP 的生命期 a

（ s ）

0 41.4

1x10-5 39.5

2x10-5 39.7

5x10-5 36.3

1x10-4 33.0

2x10-4 28.6

5x10-4 21.0

1x10-3 14.3

a. Monitored at 480nm

0 200 400 600 800

0

1000

2000

3000

4000

5000

0.0000 0.0002 0.0004 0.0006 0.0008 0.0010

0

20000

40000

60000

80000

τobs-1-τ

0 -1

[TEA]/M

r=0.9992

Cou

nts

Time (s)

kq = 4.52 107 M-1s-1

16

Thermodynamics of Exciplex

0.0000 0.0002 0.0004 0.0006 0.0008 0.0010

20000

25000

30000

35000

40000

45000

50000

55000

60000

0.0000 0.0002 0.0004 0.0006 0.0008 0.0010

20000

30000

40000

50000

60000

70000

0.0000 0.0002 0.0004 0.0006 0.0008 0.0010

20000

30000

40000

50000

60000

70000

80000

0.0000 0.0002 0.0004 0.0006 0.0008 0.0010

20000

30000

40000

50000

60000

70000

80000

0.0000 0.0002 0.0004 0.0006 0.0008 0.0010

20000

30000

40000

50000

60000

70000

80000

0.0000 0.0002 0.0004 0.0006 0.0008 0.0010

20000

30000

40000

50000

60000

70000

80000

90000

kq=3.96E7

[TEA] / M

20 ℃

kq=4.29E7

[TEA] / M

PBP-TEA

kq=4.91E7

30 ℃

[TEA] / M

40 ℃

kq=5.49E7

[TEA] / M

50 ℃

kq=5.86E7

[TEA] / M

10 ℃

τobs

-1

60 ℃

kq=6.27E7

[TEA] / M

0.0030 0.0031 0.0032 0.0033 0.0034 0.0035 0.0036

17.5

17.6

17.7

17.8

17.9

18.0

ln (

k q)

1/T (1/K)

T （℃） kq × 10–7 （ M-1s-1 ）

10 3.96

20 4.29

30 4.91

40 5.49

50 5.86

60 6.27

Arrhenius plot

kq = Aexp(-E‡a/RT)

E‡a=1.8 kcal/mol

17

400 450 500 550 600 650 700-10

0

10

20

30

40

50

60

70 10C 20C 30C 40C 50C 60C

Re

lativ

e In

ten

sity

Wavelength(nm)

Stevens-Ban plot

0.0030 0.0031 0.0032 0.0033 0.0034 0.0035 0.0036-1.10

-1.05

-1.00

-0.95

-0.90

-0.85

-0.80

-0.75

-0.70

-0.65

Ea = 2.0 kcal/mol Slope = -Ea/R = -1014

Slope = -H/R = 1434

H = -2.8 kcal/mol

ln[Φ

(CT)/Φ

(LE)]

1/T (1/K)

Thermodynamics of Exciplex

ln[(CT)/(LE)] = A H/RT

18

Potential Energy Curve

hvLE = 59.6 kcal/mol hvCT = 44.0 kcal/mol

LE

CT

Ea = 1.8 kcal/mol

Erep(LE) Erep(CT)

H

E

= -2.8 kcal/mol

= 13.7 kcal/mol= 26.5 kcal/mol

rD-A

Erep(LE) = E LE hvLE

Erep(CT) = E LE hvCT H

19

0.0000 0.0005 0.001010000

20000

30000

40000

50000

60000

70000

80000

90000

100000

110000

120000

130000

140000

τobs

-1

[amine] / M

PA DEA DPA TEA TPA TiPA

各種胺類在室溫的 Stern-Volmer plot

N N

N

N

H

N

H

N

H

H

triethylamine (TEA) tripropylamine (TPA) triisopropylamine (TiPA)

dipropylamine (DPA) diethylamine (DEA) propylamine (PA)

20

AMINEIP（ eV

）kq × 10

–7 （ M-1s-1 ） R

PA 8.78 No quenching -

DEA 8.01 2.42 0.9943

DPA 7.84 2.91 0.9932

TEA 7.50 4.52 0.9992

TPA 7.23 6.52 0.9956

TiPA 6.95 11.0 0.9994

6.8 7.0 7.2 7.4 7.6 7.8 8.07.3

7.4

7.5

7.6

7.7

7.8

7.9

8.0

8.1

log(

k q)

Ionization Potential (eV)

不同胺類的淬熄效應

21

不同溫度各種胺類的淬熄速率常數 kq×10–7(M-1s-1)

溫度（℃）

DEA DPA TEA TPA TiPA

10 2.15 2.51 3.96 5.81 15.1

20 2.32 2.75 4.29 6.34 12.8

30 2.58 3.10 4.91 6.79 9.66

40 2.92 3.35 5.49 7.16 7.82

50 3.28 3.86 5.86 7.60 6.89

60 3.72 4.17 6.27 7.97 6.53

Temperature-dependent quenching

22

0.0030 0.0031 0.0032 0.0033 0.0034 0.0035 0.003616.8

17.0

17.2

17.4

17.6

17.8

18.0

18.2

18.4

18.6

18.8

19.0

ln (

k q)

1/T (1/K)

DEA DPA TEA TPA TiPA

各種胺類的 Arrhenius plot

Temperature-dependent quenching

各種胺類淬熄參態 PBP 的活化能與前指數因子

DEA DPA TEA TPA TiPA

IP(eV) 8.01

7.84 7.50 7.23 6.95

Ea(kcal/mol)

2.08

1.94 1.80 1.17 -3.37

log A 8.92

8.89 8.98 8.67 5.57

23

PBP-TiPA 系統在不同溫度的磷光光譜

400 450 500 550 600 650 700

0

10

20

30

40

50

60

70

Rel

ativ

e In

tens

ity

Wavelength(nm)

10 C 20 C 30 C 40 C 50 C 60 C

PBP-TiPA 系統的 Stevens-Ban 圖

0.0030 0.0031 0.0032 0.0033 0.0034 0.0035 0.0036

-0.4

-0.2

0.0

0.2

0.4

0.6

Slope = - H/R = 1817

H = -3.6 kcal/mol

ln[Φ

(CT)/Φ

(LE)]

1/T(1/K)

r = 0.9873

24

Photoreduction of BP

200 300 400 500

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 min 10 min 20 min 30 min 40 min 50 min 60 min 90 min

5 E-3 M BP 照光時間

Abs

orba

nce

Wavelength(nm)

200 300 400 500

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.55 E-3 M BP + 5 E-3 M TEA 照光時間

Abs

orba

nce

Wavelength(nm)

0 min 10 min 20 min 30 min 40 min 50 min 60 min 90 min

0 20 40 60 80 100 120

0

20

40

60

80

100

未加TEA

com

posi

tion

(%)

照光時間 min（ ）

BP消逝 Benzopinacol生成 BP消逝 Benzopinacol生成

未加TEA

25

200 300 400 500

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 min 10 30 60 90 120 150 180 A

bsor

banc

e

Wavelength(nm)

2.5 E-3 M PBP 照光時間

200 300 400 500

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5照光時間2.5 E-3 M PBP + 2.5 E-3 M TEA

0 min 10 20 30 40 50 60 90 120 150

Abs

orba

nce

Wavelength(nm)

Photoreduction of PBP

26

0 2 4 6 8 10 12 14 16

0

200

400

600

800

1000

1200

1400

1600

照光時間 (min)

180 150 120

9060 50 40 30 20 10

2.5 E-3 M PBP + 2.5E-3 M TEA

mV

(R

esp

on

se)

Retention Time (min)

0

0 20 40 60 80 100 120 140 160 180

0

20

40

60

80

100

com

pos

itio

n(%

)Time(min)

4-PBP Pinacol

PBP-TEA 隨照光時間產物消長的 HPLC 圖 （ tR = 7為 PBP ， tR =11.5為 4-phenylbenzopinacol ）

Photoreduction of PBP

27

電荷 - 轉移誘導的光還原反應機構

PBP

1PBP*kISC 3PBP*

+ NEt3kq

exciplex

O

phN

CHCH3H

phph

(C2H5)2

kH

(C2H5)2N

CHCH3O

ph

H

ph

ph

photoreduction products

NEt3

hv3 *

-hv'

Photoreduction of PBP

28

BP- 系列光引發聚合反應

TMPTA 硬化前之 FTIR 圖

4000.0 3000 2000 1500 1000 450.0

0.0

10

20

30

40

50

60

70

80

90

100

110

116.1

CM-1

%T

3441.79

2970.33

1727.92

1635.27

1466.34

1408.37

1270.491187.44

1117.22

1062.37985.67 809.32

4000.0 3000 2000 1500 1000 450.0

30.0

35

40

45

50

55

60

65

70

75

80

85

90

95.1

CM-1

%T

3441.282968.06

1730.48

1644.68

1164.24

645.58

TMPTA-PBP-TEA 硬化後之 FTIR 圖

Conclusion

29

1. The photophysical analysis confirmed that the low-lying excited singlet and triplet states of PBP is 1(n, *), 3( , *) respectively. Thus, an intramolecular energy transfer has occurred from the n * of carbonyl to the * of biphenyl.

2. Direct evidence for triplet exciplex formation of excited PBP triplet with amines was provided by the observation of emission at longer wavelengths than that of the phosphorescence of PBP.

3. The quenching rate constants were dependent on the ionization potentials of amines. The trend reflects on the calculated activation energies (Ea) for exciplex formation of 3PBP and amines.

30

4. The stabilization enthalpy (H) of exciplex increases with increasing steric effect of amines from TEA to TiPA, " Entropy Control" is expected to widely contribute to the exciplex formation for PBP-TiPA system under high-temperature limit region.

5. The bimolecular reactivity of photoreduction is very fast for lowest 3(n, *), but (, *) triplet is almost unreactive without amine electron donor. A new mechanism of hydrogen atom abstraction has been proposed by rapid charge-transfer to form an exciplex with TEA following proton transfer.

6. The PBP-TEA is an efficient photoinitiator and shows the same charge-transfer induced radical’s formations that are able to initiate the polymerization of acrylic type monomers.

Conclusion

31