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

被引:111
作者
Spano, Frank C.
Meskers, Stefan C. J.
Hennebicq, Emanuelle
Beljonne, David
机构
[1] Temple Univ, Dept Chem, Philadelphia, PA 19122 USA
[2] Eindhoven Univ Technol, Lab Macromol & Organ Chem, NL-5600 MB Eindhoven, Netherlands
[3] Univ Mons, B-7000 Mons, Belgium
关键词
D O I
10.1021/ja067321g
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Photoexcitations in helical aggregates of a functionalized, chiral oligophenylenevinylene (MOPV) are described going beyond the Born-Oppenheimer approximation, in the form of dressed (polaronic) Frenkel excitons. This allows for accurate modeling of the experimentally observed 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 equilibrium that differs appreciably from the ground state due to the presence of the excited state. The absorption and emission band shape and the circular dichroism are consistent with a coherence range of the emitting excitation of approximately two neighboring molecules. 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 sigma = 0.12 eV and a spatial correlation length l(0) approximate to 5 molecules. We find that disorder and EV coupling act synergistically in localizing the emitting exciton to a single MOPV in the aggregate with 95% probability.
引用
收藏
页码:7044 / 7054
页数:11
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