State-selectivity of Excited-state Intramolecular Proton Transfer in a 'Double' Benzoxazole: Jet Spectroscopy and Semiempirical Calculations

  1. Ernsting, N.P. 2
  2. Arthen-Engeland, Th. 2
  3. Rodriguez, M.A. 1
  4. Thiel, W. 1
  1. 1 University of Wuppertal
    info

    University of Wuppertal

    Wuppertal, Alemania

    ROR https://ror.org/00613ak93

  2. 2 Max Planck Institute for Biophysical Chemistry
    info

    Max Planck Institute for Biophysical Chemistry

    Gotinga, Alemania

    ROR https://ror.org/03e76ya46

Revista:
Journal of Chemical Physics

ISSN: 0021-9606

Any de publicació: 1992

Volum: 97

Número: 6

Pàgines: 3914-3919

Tipus: Article

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Resum

We examine the fluorescence excitation spectra of free 2,5-bis(2′- benzoxazolyl)-hydroquinone (BBXHQ) cooled in a supersonic jet. By using double-resonance saturation spectroscopy, we show that adjacent vibronic transitions, leading to either blue or red fluorescence, belong to a single molecular species in the electronic ground state. The molecular geometries of the enol and keto forms which are relevant for intramolecular transfer of a single hydrogen atom in the S 1 state are obtained by the MNDO/H method. The translocation distance is calculated to be 0.43 Å. The complexity of the vibronic spectrum, near the electronic origin for the S 0( 1A g) → S 1( 1B u) transition of the enol form at 4178.1 Å, is attributed to vibronic coupling with the nonplanar excited keto form due to H tunneling. © 1992 American Institute of Physics.