Photophysical properties of the asymmetrically substituted spirobifluorenes spiro-DPO and spiro-MeO-DPO

Authors

  • Cornelia M. Brendel,

    1. Macromolecular Chemistry and Molecular Materials, Institute of Chemistry, Department of Science and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Strasse 40, 34132 Kassel, Germany
    Search for more papers by this author
  • Fernando B. Dias,

    1. Durham Photonic Materials Institute, Department of Physics, University of Durham, South Road, Durham DH1 3LE, United Kingdom
    Search for more papers by this author
  • Tobat P. I. Saragi,

    1. Macromolecular Chemistry and Molecular Materials, Institute of Chemistry, Department of Science and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Strasse 40, 34132 Kassel, Germany
    Search for more papers by this author
  • Andy P. Monkman,

    1. Durham Photonic Materials Institute, Department of Physics, University of Durham, South Road, Durham DH1 3LE, United Kingdom
    Search for more papers by this author
  • Josef Salbeck

    Corresponding author
    1. Macromolecular Chemistry and Molecular Materials, Institute of Chemistry, Department of Science and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Strasse 40, 34132 Kassel, Germany
    • Phone: +49 561 804 4425, Fax: +49 561 804 4555
    Search for more papers by this author

Abstract

The photophysical behaviour of the oxadiazolyl (PBD) and diphenylamino (TAD) substituted spirobifluorenes 2′,7′-bis-(N,N-diphenylamino)-2-(5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl)-9,9′-spirobifluoren (spiro-DPO) and 2′,7′-bis-(N,N-diphenylamino)-2-(5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl)-9,9′-spirobifluoren (spiro-MeO-DPO) has been investigated by temperature-dependent steady-state absorption and luminescence spectroscopy and gated measurements. Fluorescence and phosphorescence lifetime measurements, relative quantum yields and dipole moments of the excited states have been determined. Asymmetrically substituted spirobifluorenes exhibit charge-transfer (CT) emission due to coupling (spiroconjugation) between the fluorene fragments of spirobifluorene. They show a considerable ground-state dipole moment and exist as equilibrating conformeres. Population of the CT state only occurs after absorption to the locally excited singlet state. The CT fluorescence is dominated by the emission of two equilibrating conformeres with similar dipole moments. At low temperature they planarize in both molecular halves and show strong phosphorescence that is still detectable at room temperature.

Ancillary