Intramolecular Polarization Induces Electron–Hole Charge Separation in Light-Harvesting Molecular Triads

Artificial light-harvesting supramolecular structures reproduce the light-to-electrochemical energy transduction mechanisms observed in natural photosynthesis. Among them the prototypical carotenoid(C)–porphyrin(P)–fullerene(C 60 ) type of structures have been the most studied. Several experiments performed in such structures, and others alike, have shown that the photoexcited state C – 1 P – C 60 decays to the metastable charge-separated state C – P •+ − C 60 •– within a few picoseconds, whereas the final charge-separated state, C •+ – P − C 60 •–, is obtained within hundreds of picoseconds. This paper introduces a nonlinear polarizable extended Hückel Hamiltonian that describes the charge dynamics and charge-separation effects in such triads by means of quantum dynamics simulations performed on the photoexcited electron–hole pair. The results are interpreted on the basis of the discrete self-trapping equation and enlighten the role played by the polarizability on charge-separation phenomena.