Influence of Donor-Acceptor Distance Variation on Photoinduced Electron and Proton Transfer in Rhenium(I)-Phenol Dyads

Kuss-Petermann, Martin and Wolf, Hilke and Stalke, Dietmar and Wenger, Oliver S.. (2012) Influence of Donor-Acceptor Distance Variation on Photoinduced Electron and Proton Transfer in Rhenium(I)-Phenol Dyads. Journal of the American Chemical Society, 134 (30). pp. 12844-12854.

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Official URL: http://edoc.unibas.ch/48168/

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A homologous series of four molecules in which a phenol unit is linked covalently to a rhenium(I) tricarbonyl diimine photooxidant via a variable number of p-xylene spacers (n = 0–3) was synthesized and investigated. The species with a single p-xylene spacer was structurally characterized to get some benchmark distances. Photoexcitation of the metal complex in the shortest dyad (n = 0) triggers release of the phenolic proton to the acetonitrile/water solvent mixture; a H/D kinetic isotope effect (KIE) of 2.0 ± 0.4 is associated with this process. Thus, the shortest dyad basically acts like a photoacid. The next two longer dyads (n = 1, 2) exhibit intramolecular photoinduced phenol-to-rhenium electron transfer in the rate-determining excited-state deactivation step, and there is no significant KIE in this case. For the dyad with n = 1, transient absorption spectroscopy provided evidence for release of the phenolic proton to the solvent upon oxidation of the phenol by intramolecular photoinduced electron transfer. Subsequent thermal charge recombination is associated with a H/D KIE of 3.6 ± 0.4 and therefore is likely to involve proton motion in the rate-determining reaction step. Thus, some of the longer dyads (n = 1, 2) exhibit photoinduced proton-coupled electron transfer (PCET), albeit in a stepwise (electron transfer followed by proton transfer) rather than concerted manner. Our study demonstrates that electronically strongly coupled donor–acceptor systems may exhibit significantly different photoinduced PCET chemistry than electronically weakly coupled donor–bridge–acceptor molecules.
Faculties and Departments:05 Faculty of Science > Departement Chemie > Chemie > Anorganische Chemie (Wenger)
UniBasel Contributors:Wenger, Oliver
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Chemical Society
Note:Publication type according to Uni Basel Research Database: Journal article -- The final publication is available at American Chemical Society, see DOI link
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Last Modified:13 Jun 2018 07:16
Deposited On:05 Jan 2017 10:07

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