Hopping versus Tunneling Mechanism for Long-Range Electron Transfer in Porphyrin Oligomer Bridged Donor-Acceptor Systems
Artikel i vetenskaplig tidskrift, 2015

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.

Författare

Melina Gilbert Gatty

Chalmers, Kemi och kemiteknik, Kemi och biokemi, Fysikalisk kemi

Axel Kahnt

Chalmers, Kemi och kemiteknik, Kemi och biokemi, Fysikalisk kemi

L. J. Esdaile

University of Oxford

M. Hutin

University of Oxford

Harry L. Anderson

University of Oxford

Bo Albinsson

Chalmers, Kemi och kemiteknik, Kemi och biokemi, Fysikalisk kemi

Journal of Physical Chemistry B

1520-6106 (ISSN) 1520-5207 (eISSN)

Vol. 119 24 7598-7611

Styrkeområden

Nanovetenskap och nanoteknik

Ämneskategorier

Fysikalisk kemi

DOI

10.1021/jp5115064