Probing excitation delocalization in supramolecular chiral stacks by means of circularly polarized light : experiment and modeling

F.C. Spano, S.C.J. Meskers, E. Hennebicq, D. Beljonne

Research output: Contribution to journalArticleAcademicpeer-review

90 Citations (Scopus)

Abstract

Photoexcitations in helical aggregates of a functionalized, chiral oligophenylenevinylene (MOPV) are described going beyond the Born-Oppenheimer approxn., in the form of dressed (polaronic) Frenkel excitons. This allows for accurate modeling of the exptl. obsd. wavelength dependence of the circular polarization in fluorescence, which directly probes the non-adiabatic nature of the electron-vibration (EV) coupling in this system. The fluorescence photon is emitted from a nuclear geometry in which one MOPV and its two nearest neighbors have a nuclear equil. that differs appreciably from the ground state due to the presence of the excited state. The absorption and emission band shape and the CD are consistent with a coherence range of the emitting excitation of approx. two neighboring mols. Random fluctuations in the zero-order excited-state energy of the MOPVs (disorder) limit the exciton delocalization and can be described by a Gaussian distribution of energies with a width s = 0.12 eV and a spatial correlation length l0 ~ 5 mols. We find that disorder and EV coupling act synergistically in localizing the emitting exciton to a single MOPV in the aggregate with 95% probability. [on SciFinder (R)]
Original languageEnglish
Pages (from-to)7044-7054
JournalJournal of the American Chemical Society
Volume129
Issue number22
DOIs
Publication statusPublished - 2007

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