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Solvent-Dependent Radiationless Transitions of Excited 1-Aminonaphthalene Derivatives

Suzuki, K ; Tanabe, H ; Tobita, S ; Shizuka, H

The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory, 1997-06, Vol.101 (25), p.4496-4503 [Periódico revisado por pares]

American Chemical Society

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  • Título:
    Solvent-Dependent Radiationless Transitions of Excited 1-Aminonaphthalene Derivatives
  • Autor: Suzuki, K ; Tanabe, H ; Tobita, S ; Shizuka, H
  • É parte de: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory, 1997-06, Vol.101 (25), p.4496-4503
  • Notas: Abstract published in Advance ACS Abstracts, June 1, 1997.
    ark:/67375/TPS-5GXPS69K-M
    This work was presented at XVIIth International Conference on Photochemistry, London, U.K., August, 1995.
    istex:47BA2469A24DF4FAF85EEE630EEC2F33E11C3517
  • Descrição: Photophysical parameters in the excited singlet states of a series of 1-aminonaphthalene derivatives in cyclohexane, 3-methylpentane, and acetonitrile have been determined by means of time-resolved and steady-state fluorometry and time-resolved thermal lensing technique with the aid of MO calculations to elucidate the mechanism of internal fluorescence quenching of 1-aminonaphthalenes observed in nonpolar media. It is revealed that (1) the radiationless processes in nonpolar solvents are mainly due to fast internal conversion (IC; Φic = 0.97, k ic = 8.1 × 109 s-1 for N,N-dimethyl-1-aminonaphthalene (DMAN) in cyclohexane at 293 K), (2) the fast IC occurs predominantly in the compounds having a pretwisted and flexible amino group with respect to the naphthalene ring, and the rate remarkably depends on temperature (the activation energy for the temperature dependent IC process of DMAN in 3-methylpentane is 5.1 kcal mol-1), indicating that the IC process is linked with an internal twisting motion of the amino group in nonpolar solvents, and (3) for the pretwisted compounds the rate of the S1 → T1 intersystem crossing (ISC) is also enhanced both in nonpolar and polar solvents. On the basis of the rate parameters obtained, the IC and ISC mechanisms of 1-aminonaphthalenes are discussed together with the remarkable solvent effects on their relaxation processes.
  • Editor: American Chemical Society
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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