| Abstract
| - Quantum-chemical techniques are applied to model the mechanisms of photoinduced chargetransfer from a π-electron donating group (tetracene, D) to a π-electron-acceptor moiety (pyromellitimide,A) separated by a bridge of increasing size (p-phenylenevinylene oligomers, B). Correlated Hartree−Focksemiempirical approaches are exploited to calculate the four main parameters controlling the transfer rate(kRP) in the framework of Marcus−Jortner−Levich's formalism: (i) the electronic coupling between theinitial and final states; (ii) and (iii) the internal and external reorganization energy terms; and (iv) the variationof the free Gibbs energy. The charge transfer is shown to proceed in these compounds through twocompeting mechanisms, coherent (superexchange) versus incoherent (bridge-mediated) pathways. Whilesuperexchange is the dominant mechanism for short bridges, incoherent transfer through hopping alongthe phenylene vinylene segment takes over in longer chains (for ca. three phenylenevinylene repeat units).The influence of the chemical structure of the π-conjugated phenylenevinylene bridge on the electronicproperties and the rate of charge transfer is also investigated.
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