Hopping versus Tunneling Mechanism for Long-Range Electron Transfer in Porphyrin Oligomer Bridged Donor–Acceptor Systems

Melina Gatty, Axel Kahnt, Louisa Esdaile, Marie Hutin, Harry Anderson, Bo Albinsson

    Research output: Contribution to journalArticlepeer-review

    16 Citations (Scopus)

    Abstract

    Achieving long-range charge transport in molecular systems is interesting to foresee applications of molecules in practical devices. However, designing molecular systems with pre-defined wire-like properties remains difficult due to the lack of understanding of the mechanism for charge transfer. Here we investigate a series of porphyrin oligomer-bridged donor-acceptor systems Fc-Pn-C60 (n = 1-4, 6). In these triads, excitation of the porphyrin-based bridge generates the fully charge-separated state, Fc•+-Pn-C60•-, through a sequence of electron transfer steps. Temperature dependence of both charge separation (Fc-Pn∗-C60 → Fc-Pn•+-C60•-) and recombination (Fc•+-Pn-C60•- → Fc-Pn-C60) processes was probed by time-resolved fluorescence and femtosecond transient absorption. In the long triads, two mechanisms contribute to recombination of Fc•+-Pn-C60•- to the ground state. At high temperatures (≥280 K), recombination via tunneling dominates for the entire series. At low temperatures (<280 K), unusual crossover from tunneling to hopping occurs in long triads. This crossover is rationalized by the increased lifetimes of Fc•+-Pn-C60•-, hence the higher probability of reforming Fc-Pn•+-C60•- during recombination. We demonstrate that at 300 K, the weak distance dependence for charge transfer (β = 0.028 Å-1) relies on tunneling rather than hopping.

    Original languageEnglish
    Pages (from-to)7598-7611
    Number of pages14
    JournalThe Journal of Physical Chemistry B
    Volume119
    Issue number24
    DOIs
    Publication statusPublished - 18 Jun 2015

    Fingerprint Dive into the research topics of 'Hopping versus Tunneling Mechanism for Long-Range Electron Transfer in Porphyrin Oligomer Bridged Donor–Acceptor Systems'. Together they form a unique fingerprint.

    Cite this