Charge recombination versus charge separation in donor-bridge-acceptor systems
Artikel i vetenskaplig tidskrift, 2007

Optimizing the ratio of the rates for charge separation (CS) over charge recombination (CR) is crucial to create long-lived charge-separated states. Mastering the factors that govern the electron transfer (ET) rates is essential when trying to achieve molecular-scale electronics, artificial photosynthesis, and also for the further development of solar cells. Much work has been put into the question of how the donor-acceptor distances and donor-bridge energy gaps affect the electronic coupling, V DA , and thus the rates of ET. We present here a unique comparison on how these factors differently influence the rates for CS and CR in a porphyrin-based donor-bridge-acceptor model system. Our system contains three series, each of which focuses on a separate charge-transfer rate-determining factor, the donor-acceptor distance, the donor-bridge energy gap, and last, the influence of the electron acceptor on the rate for charge transfer. In these three series both CS and CR are governed by superexchange interactions which make a CR/CS comparative study ideal. We show here that the exponential distance dependence increases slightly for CR compared to that for CS as a result of the increased tunneling barrier height for this reaction, in accordance with the McConnell superexchange model. We also show that the dependence on the tunneling barrier height is different for CS and CR. This difference is highly dependent on the electron acceptor and thus cannot solely be explained by the differences in the frontier orbitals of the electron donor in these porphyrin systems. © 2007 American Chemical Society.

Författare

Joanna Wiberg

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

L. J. Guo

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Karin Pettersson

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Daniel Nilsson

Chalmers, Kemi- och bioteknik, Organisk kemi

Thomas Ljungdahl

Chalmers, Kemi- och bioteknik, Organisk kemi

Jerker Mårtensson

Chalmers, Kemi- och bioteknik, Organisk kemi

Bo Albinsson

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Journal of the American Chemical Society

0002-7863 (ISSN) 1520-5126 (eISSN)

Vol. 129 155-163

Ämneskategorier

NATURVETENSKAP

DOI

10.1021/ja066346c