• Title/Summary/Keyword: photoinduced transfer

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Photoionization of N,N,N',N'-Tetramethyl-p-phenylenediamine in Polar Solvents

  • Min Yeong Lee;Du Jeon Jang;Minyung Lee;Du-Jeon Jang;Dongho Kim;Sun Sook Lee;Bong Hyun Boo
    • Bulletin of the Korean Chemical Society
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    • v.12 no.4
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    • pp.429-433
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    • 1991
  • The photoinduced electron transfer reactions of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) in various polar solvents were studied by measuring time-resolved fluorescence. The temperature dependence on the fluorescence decay rate in acetonitrile, methanol, ethanol and buthanol was carried out to obtain the activation energy and Arrehnius factor for the photoinduced electron transfer reaction. It was found that as the dielectric constant of the solvent increases, the activation energy and the reaction rate increase. This implys that the Arrehnius factor is important in controlling the photoinduced electron transfer reaction rate. In water, TMPD exists in three forms (cationic, protonated and neutral forms) due to the high dielectric constant and strong proton donating power of water. The photoinduced electron transfer reaction was found to be very fast (< 50 ps) and also the long liverd component in the fluorescence decay profile attributable to the photoexcited protonated form of TMPD was observed. Probably, the reaction pathway and the reaction coordinate seem to be different depending on the solvents studied here.

PHOTOINDUCED ELECTRON TRANSFER REACTIONS OF 1,4-DIPHENYL-1,3-BUTADIYNE

  • Kim, Bang-Duk;Shim, Sang-Chul
    • Journal of Photoscience
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    • v.5 no.1
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    • pp.23-26
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    • 1998
  • Irradiation of diphenylbutadiyne (DPB) in methanol with 9,10-dicyanoanthracene (DCA) yields four methanol adducts, two more than the products obtained in the absence of DCA. Laser flash photolysis studies indicate the reaction to proceed through a photoinduced electron transfer mechanism involving DPB cation radical and DCA anion radical.

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Photoinduced Electron- and Energy-Transfer Processes in Supramolecules using Imide Compounds

  • Fujitsuka, Mamoru;Majima, Tetsuro
    • Rapid Communication in Photoscience
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    • v.3 no.1
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    • pp.1-15
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    • 2014
  • We summarize recent studies on photoinduced electron- and energy-transfer processes of various supramolecules including imide group(s) as a component. Recently, imides have been employed in various functional molecular systems, because of their excellent photophysical and electron accepting properties. Our research group also employed imides in various supramolecular systems such as donor-acceptor dyads, quantum dots, DNA, and so on. First, we summarize fundamental properties of imides such as photophysical and electrochemical properties. Then, photoinduced processes of imides in the supramolecular systems are described to show their applicability in the various fields.

Photoinduced Charge-Transfer Association of Tetracyanoquinodimethane with Aminobiphenyls

  • Kim, Yong-Hee;Jung, Sang-Don;Chung, Myung-Ae;Song, Ki-Dong;Cho, Dae-Won
    • Bulletin of the Korean Chemical Society
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    • v.29 no.5
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    • pp.948-952
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    • 2008
  • The molecular association of acceptors with electron donors is studied in the highly-polar solvent $CH_3CN$. Tetracyanoquinodimethane (TCNQ) forms a stable charge-transfer complex with donor molecules such as 4- aminobiphenyl (4-AB), benzidine (BD) and 2-aminobiphenyl (2-AB) with high association constants. The complexes of TCNQ with 4-AB or BD show new absorption bands at around 800 and 500 nm, which can be identified as reduced $TCNQ^{{\bullet}-}$ and $TCNQ^{2-}$ species, respectively. These bands grow quickly upon photoirradiation, implying that the charge-transfer complexes are easily formed in an excited state. Conversely, a small spectral manifestation of the charge transfer was observed in the case of 2-AB complex. It is demonstrated that the structural orientation between the geminate ion pairs could play an important role in building a stable complex.

Photoinduced Electron Transfer From Aromatic Amines to Triplet States of $C_{60}$

  • Yahata, Yukio;Sasaki, Yoshiko;Fujitsuka, Mamoru;Ito, Osamu
    • Journal of Photoscience
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    • v.6 no.3
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    • pp.117-121
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    • 1999
  • Photoinduced electron transfer of C60 has been studied by the laser photolysis measuring the transient absorption bands in near-IR region. The electron transfer aromatic amines via the triplet state of C60 is confirmed by the decay of the transient absorption bands of the triplet state of C60 and the rise of the anion radical of C60 and the cation radicals of amines. The rate and efficiency of electron transfer are strongly affected by the donor ability of amines and polarity of solvents. Back electron-transfer kinetics is also strongly affected by the solvent polarity.

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Zinc Porphyrin-Cored Dendrimers; Axial Coordination of Pyridine and Photoinduced Electron Transfer to Methyl Viologen

  • Park, Ji-Eun;Choi, Dae-Ock;Shin, Eun-Ju
    • Bulletin of the Korean Chemical Society
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    • v.32 no.12
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    • pp.4247-4252
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    • 2011
  • The porphyrin-incorporated arylether dendrimers ZnP-D1 and ZnP-D4 were investigated to discover the influence of dendritic environments for the axial ligation of pyridine and photoinduced electron transfer by methyl viologen. Absorption and fluorescence spectra of ZnP, ZnP-D1, and ZnP-D4 were measured in dichloromethane with the addition of pyridine or methyl viologen dichloride. Axial ligation of pyridine was confirmed by red-shifted absorption spectrum. The complex formation constants $K_f$ (Table 1) for axial coordination of pyridine on ZnP, ZnP-D1, and ZnP-D4 were estimated to be $4.4{\times}10^3\;M^{-1}$, $3.3{\times}10^3\;M^{-1}$, and $1.7{\times}10^3\;M^{-1}$, respectively. The photoinduced electron transfer to methyl viologen dichloride was confirmed by fluorescence quenching. Stern-Volmer constants Ksv for ZnP, ZnP-D1, and ZnP-D4 were calculated to be $2.6{\times}10^3$, $2.5{\times}10^3$, and $2.1{\times}10^3$, respectively. ZnP-D4 surrounded by 4 aryl ether dendrons shows the smallest $K_f$ and Ksv values, with comparison to ZnP and ZnP-D1.

Photoinduced Electron Transfer from Excited Ruthenium Complexes at Nanocrystalline $TiO_2$ Electrodes

  • 배종현;김동환;김영일;김강진
    • Bulletin of the Korean Chemical Society
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    • v.18 no.6
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    • pp.567-573
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    • 1997
  • Photoinduced electron transfer from the charge-transfer excited states of Ru(tpy)(bpy(COOH)₂)$CN^+$, Ru(tpy)(bpy(COOH)₂)$Cl^+$, Ru(tpy)(bpy(COOH)₂)H₂+O², and Ru(tpy)(bqu(COOH)₂)$Cl^+$ to the conduction band of TiO₂ has been studied through photoelectrochemical methods. Ru(tpy)(bpy(COOH)₂)$CN^+$ produced the highest current density and open-circuit photovoltage, whereas Ru(tpy)(bqy(COOH)₂)$Cl^+$ produced the lowest values. A potential barrier was employed to explain the experimental result that the rate of the electron transfer increases with increasing the energy difference between the donor and acceptor. A sensitizer with a high current density yielded a high photovoltage and a high conversion efficiency. The reduction rate of the oxidized sensitizer decreased with the increases in the reduction potential of the sensitizer, resulting in a poor stability of a photoelectrochemical cell.