Excited-state dynamics of naphthoylnaphthvalene: valence isomerization of the lowest excited singlet state and intermolecular hydrogen-atom abstraction of the lowest excited triplet state

Nakayama, Toshihiro; Nagahara, Tetsuhiko; Miki, Satoshi; Hamanoue, Kumao

doi:10.1016/s0009-2614(97)00047-x

Cited by 6 publications

(2 citation statements)

References 15 publications

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“…In contrast, the absorption spectra of 1-piperidino (PIAQ) and 1-pyrrodino (PYAQ) anthraquinones shown in Figure later indicate that their lowest excited singlet (S 1 ) and thus triplet (T 1 ) states are of a charge-transfer character. As an extension of our studies on the photophysics and photochemistry of aromatic carbonyl compounds with S 1 and T 1 states of no charge-transfer character, − therefore, the present paper deals with the excited-state dynamics of PXAQ (PIAQ or PYAQ) for formation of N -ylide and reduced compounds. The former product is formed from the S 1 state, while the latter product may be formed from the T 1 state, although the possibility of additional photoreduction originating from the second excited triplet state cannot be ruled out.…”

Section: Introductionmentioning

confidence: 99%

Excited-State Dynamics of 1-Piperidino- or 1-Pyrrolidino-anthraquinone for Formation of N−Ylide and Reduced Compounds

et al. 2000

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By means of subpicosecond laser photolysis of the title compound at room temperature, time-dependent shift of an absorption band has been observed at short delay times which is ascribed to solvent reorganization around the lowest excited singlet state of the solute molecule with an intramolecular charge-transfer character. In comparison with the results obtained by nanosecond laser photolysis and steady-state photolysis at 77 K, it is concluded that the lowest excited singlet state undergoes rapid intramolecular proton transfer forming an N-ylide compound. For formation of the N-ylide compound from the lowest excited singlet state of 1-piperidino-anthraquinone, it is considered that there exists an intermediate which can be ascribed to transfer of the equatorial proton to the carbonyl oxygen anion. At room temperature, no formation of N-ylide compound as a stable compound can be observed due to its rapid reversion to 1-piperidino- or 1-pyrrolidino-anthraquinone. Steady-state photolysis in ethanol at room temperature gives rise to formation of a reduced compound. Yield of the reduced compound is obtained by 405 or ≥510 nm photolysis, however, is negligibly small compared with that obtained by 313 or 366 nm photolysis. Hence, it is proposed that intersystem crossing from a higher excited singlet state (probably the second excited singlet state) to a higher excited triplet state (probably the third excited triplet state) followed by internal conversion to the lowest excited triplet (T1) state plays an important role for the photoreduction, i.e., the reduced compound may be formed from the T1 state, although the possibility of additional photoreduction originating from the second excited triplet state cannot be ruled out.

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Section: Introductionmentioning

confidence: 99%

Excited-State Dynamics of 1-Piperidino- or 1-Pyrrolidino-anthraquinone for Formation of N−Ylide and Reduced Compounds

et al. 2000

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“…(3) Formation of a hemi-Dewar-type isomer upon photolysis of 1,2-di- tert -butyl-3-trimethylsilylanthraquinone or 1,2,3-tri- tert -butylanthraquinone reported by Miki et al could be ascribed to valence isomerization in the lowest excited singlet state . (4) The decay channels for the lowest excited singlet state of naphthoylnaphthvalene (NNV) were found to be intersystem crossing to the lowest excited triplet state ( 3 NNV*) and valence isomerization yielding ground-state naphthoylnaphthalene (NN) via an intermediate (probably a zwitterionic species) . Although 3 NNV* populated in ethanol abstracted a hydrogen atom from the solvent molecule generating the NNV ketyl radical, this radical also underwent rapid valence isomerization and recombination of two NN ketyl radicals thus formed yielded 1,1,2,2-tetra-(2-naphthyl)-1,2-ethanediol (naphthopinacol).…”

Section: Introductionmentioning

confidence: 99%

Photophysics and Photochemistry of Planar Alkylanthraquinones (the 1-Methyl and 1,4-Dimethyl Compounds) Studied by Subpicosecond and Nanosecond Laser Photolysis as Well as Steady-State Photolysis

et al. 1999

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By means of subpicosecond and nanosecond laser photolysis of the title compounds (MAQ and DMAQ), it is concluded that both the lowest excited singlet and triplet states undergo intramolecular hydrogen-atom transfer and the corresponding excited biradicals thus generated yield 9-hydroxy-1,10-anthraquinone-1-methide from MAQ and 9-hydroxy-4-methyl-1,10-anthraquinone-1-methide from DMAQ. Although these methides are stable at 77 K, they revert to the original anthraquinones at a higher temperature than 77 K. In ethanol and EPA (diethyl ether-isopentane-ethanol in 5:5:2 volume ratio) at room temperature, furthermore, 313 or 366 nm steady-state photolysis reveals that 1-methyl-9,10-dihydroxyanthracene (MAQH 2 ) is formed from MAQ irrespective of the excitation wavelength but 1,4-dimethyl-9,10-dihydroxyanthracene (DMAQH 2 ) is formed from DMAQ only upon 313 nm excitation. Undoubtedly, the lowest excited triplet state of MAQ abstracts a hydrogen atom from ethanol generating the semiquinone radical followed by formation of MAQH 2 . In contrast, not the lowest excited triplet state but the third excited singlet or triplet state of DMAQ may abstract a hydrogen atom from ethanol yielding DMAQH 2 finally.

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Further study on intramolecular hydrogen-atom transfer originating from the lowest excited triplet state of 2-methylbenzophenone

Nakayama

Torii

Nagahara

et al. 1998

Journal of Photochemistry and Photobiology A: Chemistry

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Excited-state dynamics of naphthoylnaphthvalene: valence isomerization of the lowest excited singlet state and intermolecular hydrogen-atom abstraction of the lowest excited triplet state

Cited by 6 publications

References 15 publications

Excited-State Dynamics of 1-Piperidino- or 1-Pyrrolidino-anthraquinone for Formation of N−Ylide and Reduced Compounds

Excited-State Dynamics of 1-Piperidino- or 1-Pyrrolidino-anthraquinone for Formation of N−Ylide and Reduced Compounds

Photophysics and Photochemistry of Planar Alkylanthraquinones (the 1-Methyl and 1,4-Dimethyl Compounds) Studied by Subpicosecond and Nanosecond Laser Photolysis as Well as Steady-State Photolysis

Further study on intramolecular hydrogen-atom transfer originating from the lowest excited triplet state of 2-methylbenzophenone

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