Breakdown of the mirror image symmetry in the optical absorption/emission spectra of oligo(para-phenylene)s

Georg Heimel, Maria Daghofer, Johannes Gierschner, Emil J.W. List, Andrew C. Grimsdale, Klaus Müllen, David Beljonne, Jean-Luc Bredas, Egbert Zojer

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100 Scopus citations

Abstract

The absorption and emission spectra of most luminescent, π-conjugated, organic molecules are the mirror image of each other. In some cases, however, this symmetry is severely broken. In the present work, the asymmetry between the absorption and fluorescence spectra in molecular systems consisting of para-linked phenyl rings is studied. The vibronic structure of the emission and absorption bands is calculated from ab initio quantum chemical methods and a subsequent, rigorous Franck-Condon treatment. Good agreement with experiment is achieved. A clear relation can be established between the strongly anharmonic double-well potential for the phenylene ring librations around the long molecular axis and the observed deviation from the mirror image symmetry. Consequences for related compounds and temperature dependent optical measurements are also discussed.

Original languageEnglish (US)
Article number054501
JournalJournal of Chemical Physics
Volume122
Issue number5
DOIs
StatePublished - Aug 9 2005

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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