Lowest excited state of oxovanadyl(IV) tetraphenylporphyrin

Sae Chae Jeoung, Dongho Kim, Sang June Hahn, Su Young Ryu, Minjoong Yoon

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

The excited-state relaxation dynamics and pathways of oxovanadyl(IV) tetraphenylporphyrin (OVIVTPP) have been investigated by nanosecond time-resolved and steady-state emission, transient absorption, and transient resonance Raman spectroscopies. At room temperature, the emission spectrum shows a single broad featureless band centered near 790 nm in noncoordinating solvents such as toluene and benzene and at 814 nm in tetrahydrofuran (THF), whereas at 77 K the emission bands in the same solvents exhibit blue-shifts to 745 and 784 nm, respectively. Furthermore, the emission decay time in benzene increases from 40 to 60 ns with a decrease in temperature from 323 to 268 K. In contrast, the decay time in THF is ca. 10 ns, which is almost independent of temperature. The energy separation between the tripdoublet state (2T(π,π*)) and the tripquartet one (4T(π,π*)) under the proposed relaxation scheme of photoexcited OVIVTPP has been estimated to be ca. 500 cm-1 in benzene and toluene. The transient absorption spectra at room temperature denote a broad featureless absorption centered at around 480 nm with a ground-state bleaching at 555 nm. All the spectroscopic results including the transient Raman spectra led us to conclude that the electronic nature of the lowest excited state should be the tripquartet state (4T(π,π*)) at ambient temperature. The decay times for both photoinduced absorption and bleaching are similar and also in good accordance with the emission decay times as long as temperature and solvent are the same. The time-resolved emission spectra and wavelength dependent decay kinetics at 77 K reveal that the observed emission spectra apparently originate from three different emitting species. These observations are discussed in terms of postulating a quenching state (Q), which is thermally accessible from the tripdoublet state (2T(π,π*)) of OVIVTPP at room temperature.

Original languageEnglish
Pages (from-to)315-322
Number of pages8
JournalJournal of Physical Chemistry A
Volume102
Issue number2
DOIs
Publication statusPublished - 1998 Jan 8

Fingerprint

Excited states
excitation
decay
Benzene
emission spectra
benzene
bleaching
tetrahydrofuran
Temperature
Toluene
Bleaching
toluene
room temperature
blue shift
ambient temperature
temperature
tetraphenylporphyrin
Ground state
Raman spectroscopy
quenching

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry

Cite this

Jeoung, Sae Chae ; Kim, Dongho ; Hahn, Sang June ; Ryu, Su Young ; Yoon, Minjoong. / Lowest excited state of oxovanadyl(IV) tetraphenylporphyrin. In: Journal of Physical Chemistry A. 1998 ; Vol. 102, No. 2. pp. 315-322.
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abstract = "The excited-state relaxation dynamics and pathways of oxovanadyl(IV) tetraphenylporphyrin (OVIVTPP) have been investigated by nanosecond time-resolved and steady-state emission, transient absorption, and transient resonance Raman spectroscopies. At room temperature, the emission spectrum shows a single broad featureless band centered near 790 nm in noncoordinating solvents such as toluene and benzene and at 814 nm in tetrahydrofuran (THF), whereas at 77 K the emission bands in the same solvents exhibit blue-shifts to 745 and 784 nm, respectively. Furthermore, the emission decay time in benzene increases from 40 to 60 ns with a decrease in temperature from 323 to 268 K. In contrast, the decay time in THF is ca. 10 ns, which is almost independent of temperature. The energy separation between the tripdoublet state (2T(π,π*)) and the tripquartet one (4T(π,π*)) under the proposed relaxation scheme of photoexcited OVIVTPP has been estimated to be ca. 500 cm-1 in benzene and toluene. The transient absorption spectra at room temperature denote a broad featureless absorption centered at around 480 nm with a ground-state bleaching at 555 nm. All the spectroscopic results including the transient Raman spectra led us to conclude that the electronic nature of the lowest excited state should be the tripquartet state (4T(π,π*)) at ambient temperature. The decay times for both photoinduced absorption and bleaching are similar and also in good accordance with the emission decay times as long as temperature and solvent are the same. The time-resolved emission spectra and wavelength dependent decay kinetics at 77 K reveal that the observed emission spectra apparently originate from three different emitting species. These observations are discussed in terms of postulating a quenching state (Q), which is thermally accessible from the tripdoublet state (2T(π,π*)) of OVIVTPP at room temperature.",
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Lowest excited state of oxovanadyl(IV) tetraphenylporphyrin. / Jeoung, Sae Chae; Kim, Dongho; Hahn, Sang June; Ryu, Su Young; Yoon, Minjoong.

In: Journal of Physical Chemistry A, Vol. 102, No. 2, 08.01.1998, p. 315-322.

Research output: Contribution to journalArticle

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