Cyanobuta-1,3-dienes as Novel Electron Acceptors for Photoactive Multicomponent Systems

Authors

  • Dr. Francesca Tancini,

    1. Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zürich (Switzerland), Fax: (+41) 44-632-1109
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    • These authors equally contributed to this work.

  • Dr. Filippo Monti,

    1. Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 0516399844
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    • These authors equally contributed to this work.

  • Dr. Kara Howes,

    1. Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zürich (Switzerland), Fax: (+41) 44-632-1109
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  • Dr. Abdelhalim Belbakra,

    1. Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 0516399844
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  • Dr. Andrea Listorti,

    1. Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 0516399844
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  • Dr. W. Bernd Schweizer,

    1. Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zürich (Switzerland), Fax: (+41) 44-632-1109
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  • Dr. Philippe Reutenauer,

    1. Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zürich (Switzerland), Fax: (+41) 44-632-1109
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  • Dr. José-Lorenzo Alonso-Gómez,

    1. Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zürich (Switzerland), Fax: (+41) 44-632-1109
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  • Dr. Claudio Chiorboli,

    1. Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche, Sezione di Ferrara, Via L. Borsari 46, 44100 Ferrara (Italy)
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  • Lorenz M. Urner,

    1. Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zürich (Switzerland), Fax: (+41) 44-632-1109
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  • Dr. Jean-Paul Gisselbrecht,

    1. Laboratoire d'Electrochimie et de Chimie Physique du Corps Solide, Institut de Chimie-UMR 7177, CNRS, Université de Strasbourg, 4, rue Blaise Pascal, 67081 Strasbourg Cedex (France)
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  • Prof. Dr. Corinne Boudon,

    1. Laboratoire d'Electrochimie et de Chimie Physique du Corps Solide, Institut de Chimie-UMR 7177, CNRS, Université de Strasbourg, 4, rue Blaise Pascal, 67081 Strasbourg Cedex (France)
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  • Dr. Nicola Armaroli,

    Corresponding author
    1. Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 0516399844
    • Nicola Armaroli, Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 0516399844

      François Diederich, Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zürich (Switzerland), Fax: (+41) 44-632-1109

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  • Prof. Dr. François Diederich

    Corresponding author
    1. Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zürich (Switzerland), Fax: (+41) 44-632-1109
    • Nicola Armaroli, Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 0516399844

      François Diederich, Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zürich (Switzerland), Fax: (+41) 44-632-1109

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Abstract

The synthesis, electrochemical, and photophysical properties of five multicomponent systems featuring a ZnII porphyrin (ZnP) linked to one or two anilino donor-substituted pentacyano- (PCBD) or tetracyanobuta-1,3-dienes (TCBD), with and without an interchromophoric bridging spacer (S), are reported: ZnP-S-PCBD (1), ZnP-S-TCBD (2), ZnP-TCBD (3), ZnP-(S-PCBD)2 (4), and ZnP-(S-TCBD)2 (5). By means of steady-state and time-resolved absorption and luminescence spectroscopy (RT and 77 K), photoinduced intramolecular energy and electron transfer processes are evidenced, upon excitation of the porphyrin unit. In systems equipped with the strongest acceptor PCBD and the spacer (1, 4), no evidence of electron transfer is found in toluene, suggesting ZnP→PCBD energy transfer, followed by ultrafast (<10 ps) intrinsic deactivation of the PCBD moiety. In the analogous systems with the weaker acceptor TCBD (2, 5), photoinduced electron transfer occurs in benzonitrile, generating a charge-separated (CS) state lasting 2.3 μs. Such a long lifetime, in light of the high Gibbs free energy for charge recombination (ΔGCR=−1.39 eV), suggests a back-electron transfer process occurring in the so-called Marcus inverted region. Notably, in system 3 lacking the interchromophoric spacer, photoinduced charge separation followed by charge recombination occur within 20 ps. This is a consequence of the close vicinity of the donor–acceptor partners and of a virtually activationless electron transfer process. These results indicate that the strongly electron-accepting cyanobuta-1,3-dienes might become promising alternatives to quinone-, perylenediimide-, and fullerene-derived acceptors in multicomponent modules featuring photoinduced electron transfer.

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