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

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)

Pathways for resonant energy transfer in oligo(phenylenevinylene)-fullerene dyads : an atomistic model

Fast resonant energy transfer (RET) takes place from oligo(phenylenevinylene) (OPVn) segments to C60 in OPVn-C60 dyads as a result of the presence of multiple energy-transfer pathways and of significant electronic couplings (when going beyond the point-dipole model)

"Reduced" Distributed Monopole Model for the Efficient Prediction of Energy Transfer in Condensed Phases

We propose a methodology for the realistic simulation and prediction of resonance energy transfer in condensed phases based on a combination of computer simulations of phase morphologies and of a distributed monopole model for the radiationless transfer. The heavy computational demands of the method are moderated by the introduction of a transition charges reduction scheme, originally developed for ground state interactions [Berardi, R. et al. Chem. Phys. Lett. 2004, 389, 373]. We demonstrate the scheme for a condensed glass phase formed by perylene monoimide end-capped 9,9-(di n,n)octylfluorene trimers, recently studied as light-harvesting materials, where we couple a coarse-grained Monte Carlo simulation of the molecular organization and a master equation approach modeling the energy diffusion process

Pathways for resonant energy transfer in oligo(phenylenevinylene)-fullerene dyads : an atomistic model

Fast resonant energy transfer (RET) takes place from oligo(phenylenevinylene) (OPVn) segments to C60 in OPVn-C60 dyads as a result of the presence of multiple energy-transfer pathways and of significant electronic couplings (when going beyond the point-dipole model)