Abstract
Quantum-chemical techniques are applied to model the mechanisms of photoinduced charge transfer 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-Fock semiempirical 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 the initial and final states; (ii) and (iii) the internal and external reorganization energy terms; and (iv) the variation of the free Gibbs energy. The charge transfer is shown to proceed in these compounds through two competing mechanisms, coherent (superexchange) versus incoherent (bridge-mediated) pathways. While superexchange is the dominant mechanism for short bridges, incoherent transfer through hopping along the 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 electronic properties and the rate of charge transfer is also investigated.
Original language | English (US) |
---|---|
Pages (from-to) | 4436-4447 |
Number of pages | 12 |
Journal | Journal of the American Chemical Society |
Volume | 124 |
Issue number | 16 |
DOIs | |
State | Published - Apr 24 2002 |
Externally published | Yes |
ASJC Scopus subject areas
- Catalysis
- General Chemistry
- Biochemistry
- Colloid and Surface Chemistry