Photoinduced electron transfer has been observed in a molecular triad, consisting of a porphyrin (P) covalently linked to a tetrathiafulvalene (TTF) and a fullerene derivative (C60), in the different phases of the liquid crystal E-7 and in a glass of 2-methyltetrahydrofuran (2-MeTHF) by means of time-resolved electron paramagnetic resonance (EPR) spectroscopy. In both solvents, an EPR signal observed immediately after excitation has been assigned to the radical pair, based on its magnetic interaction parameters and spin polarization pattern. In the 2-MeTHF glass and the crystalline phase of E-7, the radical pair is formed from the TTF-1P-C60 singlet state. Long-lived charge separation (8 ís) for the singlet-born radical pair is observed in the 2-MeTHF glass at cryogenic temperatures. In the nematic phase of E-7, a high degree of ordering in the liquid crystal is achieved by the molecular triad. In this phase, both singlet- and triplet-initiated electron transfer routes are concurrently active. At room temperature in the presence of the external magnetic field, the triplet-born radical pair has a lifetime of 7 ís, while that of the singlet-born radical pair is much shorter (<1 ís). The difference in lifetimes is ascribed to spin dynamic effects in the magnetic field.

Photoinduced long-lived charge separation in a tetrathiafulvalene-porphyrin-fullerene triad detected by time-resolved electron paramagnetic resonance

DI VALENTIN, MARILENA;CARBONERA, DONATELLA
2005

Abstract

Photoinduced electron transfer has been observed in a molecular triad, consisting of a porphyrin (P) covalently linked to a tetrathiafulvalene (TTF) and a fullerene derivative (C60), in the different phases of the liquid crystal E-7 and in a glass of 2-methyltetrahydrofuran (2-MeTHF) by means of time-resolved electron paramagnetic resonance (EPR) spectroscopy. In both solvents, an EPR signal observed immediately after excitation has been assigned to the radical pair, based on its magnetic interaction parameters and spin polarization pattern. In the 2-MeTHF glass and the crystalline phase of E-7, the radical pair is formed from the TTF-1P-C60 singlet state. Long-lived charge separation (8 ís) for the singlet-born radical pair is observed in the 2-MeTHF glass at cryogenic temperatures. In the nematic phase of E-7, a high degree of ordering in the liquid crystal is achieved by the molecular triad. In this phase, both singlet- and triplet-initiated electron transfer routes are concurrently active. At room temperature in the presence of the external magnetic field, the triplet-born radical pair has a lifetime of 7 ís, while that of the singlet-born radical pair is much shorter (<1 ís). The difference in lifetimes is ascribed to spin dynamic effects in the magnetic field.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2439784
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