Time-resolved EPR investigation of charge recombination to a triplet state in a carotene-diporphyrin triad

M. Di Valentin, A. Bisol, G. Agostini, A. L. Moore, T. A. Moore, D. Gust, R. E. Palacios, S. L. Gould, D. Carbonera

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Abstract

Photoinduced charge separation and recombination were investigated in a triad consisting of a carotenoid (C), a tetraarylporphyrin (P) and a tris(heptafluoropropyl)porphyrin (P F ), C-P-P F , by means of time-resolved electron paramagnetic resonance. The electron transfer process was studied in a glass of 2-methyltetrahydrofuran at 10K, in the crystalline phase at 150K and in the liquid nematic phase of the uniaxial LC E-7 at 295K, and in the nematic phase of the LC ZLI-1167 at 300K. In all the different media and in the different phases, the molecular triad undergoes two-step photoinduced electron transfer, with the generation of a long-lived charge-separated state (C •+ -P-), and charge recombination to the triplet state, localized in the carotene moiety 3 C-P-P F . Low-temperature charge separation and triplet recombination are common features of both fullerene-based and diporphyrin molecular triads, proving that the large delocalized -electron system of the porphyrin electron acceptor leads to low total reorganization energy and low sensitivity to solvent stabilization of the radical ions in a similar way as for fullerene systems.

Original languageEnglish
Pages (from-to)1595-1607
Number of pages13
JournalMolecular Physics
Volume104
Issue number10-11
DOIs
Publication statusPublished - May 20 2006

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ASJC Scopus subject areas

  • Biophysics
  • Molecular Biology
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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