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

Abstract

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(C60) type of structures have been the most studied. Several experiments performed in such structures, and others alike, have shown that the photoexcited state C– 1P–C60 decays to the metastable charge-separated state C– P•+ −C60•– within a few picoseconds, whereas the final charge-separated state, C•+– P −C60•–, 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.