Intersystem Crossing versus Electron Transfer in Porphyrin-Based Donor-Bridge-Acceptor Systems: Influence of a Paramagnetic Species
Journal article, 2004

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 Angstrom, and the bridging chromophore varies from g-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 photoincluced 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.


Karin Pettersson

Chalmers, Chemical and Biological Engineering, Physical Chemistry

K. Kilsa

Uppsala University


Jerker Mårtensson

Chalmers, Chemical and Biological Engineering, Organic Chemistry

Bo Albinsson

Chalmers, Chemical and Biological Engineering, Physical Chemistry

Journal of the American Chemical Society

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

Vol. 126 21 6710-6719

Subject Categories

Physical Chemistry



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