http://www.cnr.it/ontology/cnr/individuo/prodotto/ID51116
Photoinduced Energy and Electron Transfer Processes in Porphyrin-Perylene Bisimide Symmetric Triads (Articolo in rivista)
- Type
- Label
- Photoinduced Energy and Electron Transfer Processes in Porphyrin-Perylene Bisimide Symmetric Triads (Articolo in rivista) (literal)
- Anno
- 2008-01-01T00:00:00+01:00 (literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
- 10.1021/jp7109516 (literal)
- Alternative label
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
- Marco Ghirotti; Claudio Chiorboli; Chang-Cheng You; Frank Würthner; Franco Scandola (literal)
- Pagina inizio
- Pagina fine
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
- Rivista
- Note
- ISI Web of Science (WOS) (literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
- Dipartimento di Chimica, UniVersita` di Ferrara, 44100 Ferrara, Italy,
ISOF-CNR, Sezione di Ferrara, 44100 Ferrara, Italy,
INSTM, Sezione di Ferrara, 44100 Ferrara, Italy,
Institut fur Organische Chemie,
UniVersitat Wurzburg, 97074 Wurzburg, Germany (literal)
- Titolo
- Photoinduced Energy and Electron Transfer Processes in Porphyrin-Perylene Bisimide Symmetric Triads (literal)
- Abstract
- The photophysics of two symmetric triads, (ZnP)2PBI and (H2P)2PBI, made of two zinc or free-base porphyrins
covalently attached to a central perylene bisimide unit has been investigated in dichloromethane and in toluene.
The solvent has been shown to affect not only quantitatively but also qualitatively the photophysical behavior.
A variety of intercomponent processes (singlet energy transfer, triplet energy transfer, photoinduced charge
separation, and recombination) have been time-resolved using a combination of emission spectroscopy and
femtosecond and nanosecond time-resolved absorption techniques yielding a very detailed picture of the
photophysics of these systems. The singlet excited state of the lowest energy chromophore (perylene bisimide
in the case of (ZnP)2PBI, porphyrin in the case of (H2P)2PBI) is always quantitatively populated, besides by
direct light absorption, by ultrafast singlet energy transfer (few picosecond time constant) from the higher
energy chromophore. In dichloromethane, the lowest excited singlet state is efficiently quenched by electron
transfer leading to a charge-separated state where the porphyrin is oxidized and the perylene bisimide is
reduced. The systems then go back to the ground state by charge recombination. The four charge separation
and recombination processes observed for (ZnP)2PBI and (H2P)2PBI in dichloromethane take place in the
sub-nanosecond time scale. They obey standard free-energy correlations with charge separation lying in the
normal regime and charge recombination in the Marcus inverted region. In less polar solvents, such as toluene,
the energy of the charge-separated states is substantially lifted leading to sharp changes in photophysical
mechanism. With (ZnP)2PBI, the electron-transfer quenching is still fast, but charge recombination takes
place now in the nanosecond time scale and to triplet state products rather than to the ground state. Triplettriplet
energy transfer from the porphyrin to the perylene bisimide is also involved in the subsequent deactivation
of the triplet manifold to the ground state. With (H2P)2PBI, on the other hand, the driving force for charge
separation is too small for electron-transfer quenching, and the deactivation of the porphyrin excited singlet
takes place via intersystem crossing to the triplet followed by triplet energy transfer to the perylene bisimide
and final decay to the ground state. (literal)
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- Autore CNR
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