1

Tetrachelate Porphyrin Chromophores for Metal Oxide Semiconductor Sensitization: Effect of the Spacer Length and Anchoring Gro

up Position

Speaker：李光凡

Jonathan Rochford, Dorothy Chu, Anders Hagfeldt, and Elena Galoppini

J. Am. Chem. Soc. 2007, 129, 4655 -4665

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Photoinduced Electron Transfer from Molecules to Semiconductor Nanopar

ticles

Lian, T. Coord. Chem. Rev. 2004, 248, 1231.

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Different Ways of Anchoring Molecules on Surfaces

Grätzel, M. Coord. Chem. Rev. 1998, 177, 347

4

Structures of Dyes

Durrant, J. R. J. Am. Chem. Soc. 2004, 126, 5225.

5

Work Principle of DSSCs

Grätzel, M. Inorg. Chem. 2005, 44, 6841.

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“Rigid-rod” and “Tripodal”

J. Phys. Chem. B, 2004, 108, 16642-16653

J. Phys. Chem. B, 2006 110, 15735

J. AM. CHEM. SOC. 2002, 124, 7801-7811

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Structures of The Porphyrins

Sanders, J. J. Chem.Soc. Chem. Commun. 1991, 575.-[E]-[A]-[S]

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Synthesis of the Porphyrin Sensitizers

O

O

N

N

Cl

Cl

2,3-dichloro-5,6-dicyanoquinonert 12h

22-30%

86-92%

68-82%68-76%

rt 12h

rt 3 days

rt 3h

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Synthesis of 4a

Sonogashira coupling reaction

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FT-IR-ATR Spectra of p-ZnTCPP and m-ZnTCPP

v(C=O)

v(C-O)

asymmetric v(CO2-)symmetric v(CO2

-)

v(C=O)

symmetric v(CO2-)

N+- H bending

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FT-IR-ATR Spectra of m-ZnTCP2P and m-ZnTC(PEP)P

v(C=O) v(C=O)

v(C-O) v(C-

O)

asymmetric v(CO2-)

v(C=O)

symmetric v(CO2-)

v(C≡C)

N+-H bending

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12

Main Binding Modes of The Carboxylate Group to TiO2

η1- κ2- μ2-

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Solution UV-Vis Absorption and Fluorescence Emission Data

UV-vis absorption fluorescence

porphyrinSoret λ max, nm

(ε × 105, M-1 L-1)

Q(1,0) λ max, nm

(ε × 104, M-1 L-1)

Q(0,0) λ max, nm

(ε × 104, M-1L-1) λ max, nm (Φ  )

(1e) p-ZnTCPP-[S] 424 (2.78) 557 (1.39) 597 (0.53) 606, 658 (0.023)

(2e) m-ZnTCPP-[S] 423 (4.44) 558 (2.09) 597 (0.66) 604, 657 (0.016)

(3e) m-ZnTCP2P-[S] 424 (5.51) 558 (2.77) 597 (0.96) 605, 659 (0.017)

(4e) m-ZnTC(PEP)P-[S] 425 (5.93) 558 (2.63) 598 (0.83) 604, 659 (0.018)

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UV-vis Spectra and Fluorescence Emission Spectra of 1e、 2e、 3e、 4e

λexc = 565 nm

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UV-vis Spectra of 1e、 2e、 3e、 4e on TiO2/G

Thick ~ 10μm

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UV-vis Absorption Spectra of 1d、 2d、3d、 4d and 1e、 2e、 3e、 4e on ZnO/

G

Thick ~ 2μm

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Fluorescence Emission Spectra of 1e、 2e、 3e、 4e on ZrO2/G

λexc = 565 nm

Ebg ~ 5 eV for ZrO2

Ebg ~ 3 eV for TiO2 and ZnO

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Surface Coverage

Coverage

p-ZnTCPP-[S] 27 μ mol g-1

m-ZnTCPP-[S] 20 μ mol g-1

m-ZnTCP2P-[S] 19 μ mol g-1

m-ZnTTC(PEP)P-[S] 12 μ mol g-1

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Calculated Molecular Dimensions of p-TCPP

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Calculated Molecular Dimensions of m-ZnTCPP, m-ZnTCP2P, and m-ZnTC(PEP)

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Solution Redox Potentials of 1c、 2c、3c、 4c in CH2Cl2

oxidation (V)

reduction (V)

porphyrin 1st 2nd 1st 2nd 3rdE0-0 (e

V)E1/2(P

+/P*) (eV)

(1c) p-ZnTCPP-[E] 1.10 1.47 -1.12 -1.46 -1.64 2.06 -1.04

(2c) m-ZnTCPP-[E] 1.11 1.38 -1.08 -1.45   2.07 -1.04

(3c) m-ZnTCP2P-[E] 1.12 1.37 -1.08 -1.31 -1.46 2.07 -1.05

(4c) m-ZnTC(PEP)P-[E]

1.11 1.38 -1.09 -1.33 -1.46 2.07 -1.04

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CV and DPV of 4c and 4e

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Redox Potentials of 1e、 2e、 3e、 4e Bound to TiO2/ITO and ZnO/ITO Films vers

us NHE

TiO2/ITO (V) ZnO/ITO (V)

porphyrin 1st 2ndE0-0

(eV)

E1/2(P+/P*)

(eV)1st 2nd

E0-0

(eV)

E1/2(P+/P*)

(eV)

(1e) p-ZnTCPP-[S] 1.09 1.38 2.03 -1.06 1.07 1.43 2.03 -1.04

(2e) m-ZnTCPP-[S] 1.10 1.36 2.06 -1.04 1.06 1.42 2.06 -1.00

(3e) m-ZnTCP2P-[S] 1.09 1.35 2.06 -1.03 1.07 1.42 2.05 -1.02

(4e) m-ZnTC (PEP)P-[S] 1.10 1.36 2.06 -1.04 1.04 1.41 2.05 -0.99

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Photocurrent Action Spectra of 1e、 2e、3e、 4e

FTO = fluorine-doped tin-oxide

59%

19%

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Photoelectrochemical Properties of 1e、 2e、 3e、 4e

      IPCE (%)

porphyrin Isc (mA cm-2) Voc (V) ff 430 nm 570 nm 600 nm

(1e) p-ZnTCPP-[S] 0.39 0.44 0.54 18.50 1.44 (0.08) 0.86 (0.05)

(2e) m-ZnTCPP-[S] 3.33 0.51 0.41 58.60 29.40 (0.50) 16.30 (0.28)

(3e) m-ZnTCP2P-[S] 3.72 0.50 0.42 56.90 34.50 (0.61) 21.10 (0.37)

(4e) m-ZnTC(PEP)P-[S] 1.36 0.43 0.45 25.30 9.00 (0.36) 4.81 (0.19)

IPCE = (LHE) ψinj ηc

LHE:light harvesting efficiency

ψinj:the quantum yield of charge injection

ηc :the charge collection efficiency

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Conclusions

• Four para- and meta-Zn(II) tetra(carboxyphenyl)porphyrins were studied in solution and bound to metal oxide (TiO2, ZnO, and ZrO2) nanoparticle films to determine the effect of the spacer length and anchoring group position on their photoelectrochemical and photophysical properties.

• All studies indicated that only p-ZnTCPP aggregated, suggesting close packing of the dye molecules on the semiconductor surface, and aggregation effects were not observed for the meta porphyrins.

• The greater efficiency of the rigid planar meta-substituted systems was explained in terms of a greater charge injection into the TiO2 semiconductor from rings that lie flat, and closer, to the surface.