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Updated: Jul 19, 2026

Introduction to Solid Supported Membrane Based Electrophysiology
Published on: May 11, 2013
Intersystem crossing versus electron transfer in porphyrin-based donor-bridge-acceptor systems: influence of a
Karin Pettersson1, Kristine Kilså, Jerker Mårtensson
1Department of Chemistry and Bioscience, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
Abstract:
We have investigated how the spin state of an acceptor influences the photophysical processes in a donor-bridge-acceptor (D-B-A) system. The system of choice has zinc porphyrin as the electron donor and high- or low-spin iron(III) porphyrin as the acceptor. The spin state of the acceptor porphyrin is switched simply by coordinating imidazole ligands to the metal center. The D-A center-center distance is 26 A, and the bridging chromophore varies from pi-conjugated to a sigma-bonded system. The presence of a high-spin iron(III) porphyrin in such systems has previously been shown to significantly enhance intersystem crossing in the remote zinc porphyrin donor, whereas no significant electron transfer to the iron porphyrin acceptor was observed, even though the thermodynamics would allow for photoinduced electron transfer. Here, we demonstrate that by switching the acceptor to a low-spin state, the dominating photophysical process is drastically changed; the low-spin system shows long-range electron transfer on the picosecond time-scale, and intersystem crossing occurs at its "normal" rate.
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