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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. 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. 中華民國一百年十二月二十四日. Jablonski Diagram. Photophysics. Photochemistry. 2.

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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

陳順基

明志科技大學化工系

The Exciplex Formation ofCharge-Transfer Induced 4- Phenylbenzophenone withTriethylamine and the Application in Photochemistry

中華民國一百年十二月二十四日


Jablonski diagram
Jablonski Diagram

Photophysics

Photochemistry

2


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

單態的(n , *)及(, *)性質:

參態的(n , *)及(, *)性質:

3


Molecular Complex

E

A

I

D

+

-

S

D

+

A

1

D

H

E

1

S

D

+

A

0

D

E

CT

D

H

0

D

A

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)

4


激態雙體(Excimer, Excited dimer)

(Forster et alZ. Phys. Chem. 1954)

5


激態複合體(exciplex, excited complex)

(Leonhardt et alBer. Bunsenges. Phys. Chem. 1963)

6


Photophysics of BP & PBP

BP及PBP吸收及溶劑效應

7


Vibrational structure

Vibrational structure provides clues as to which transitions are most possible

Emission of biphenyl

8


Lifetimes & Quantum yields

BP及PBP在EPA中的低溫磷光生命期

BP及PBP螢、磷光相對量子產率

9


State energy diagram

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

10


Phosphorescence Quenching of BP

a. Monitored at 450nm

11


Stern-VolmerAnalysis

a:steady-state

b:transient lifetime

c:Fouassier J. Chim Phys. 1983

12


Phosphorescence Quenching of PBP

Excitation spectra

13



Stern-VolmerPlot

kq = 4.52 107 M-1s-1

a. Monitored at 480nm

15


Thermodynamics of Exciplex

E‡a=1.8 kcal/mol

Arrhenius plot

kq = Aexp(-E‡a/RT)

16


Thermodynamics of Exciplex

Stevens-Ban plot

ln[(CT)/(LE)] = A H/RT

17


Potential Energy Curve

Erep(LE) = E LE hvLE

Erep(CT) = E LE hvCT H

18


各種胺類在室溫的Stern-Volmer plot

19



Temperature-dependent quenching

不同溫度各種胺類的淬熄速率常數kq×10–7(M-1s-1)

21


Temperature-dependent quenching

各種胺類淬熄參態PBP的活化能與前指數因子

各種胺類的Arrhenius plot

22


PBP-TiPA系統在不同溫度的磷光光譜

PBP-TiPA系統的Stevens-Ban圖

23




Photoreduction of PBP

PBP-TEA隨照光時間產物消長的HPLC圖

(tR = 7為PBP, tR =11.5為4-phenylbenzopinacol)

26


Photoreduction of PBP

電荷-轉移誘導的光還原反應機構

27


BP-系列光引發聚合反應

TMPTA-PBP-TEA硬化後之FTIR圖

TMPTA硬化前之FTIR圖

28


Conclusion
Conclusion

  • 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.

  • 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.

  • 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.

29


Conclusion1
Conclusion

  • 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.

  • 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.

  • 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.

30



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