Kinetic Isotope Effects in Reductive Excited-State Quenching of Ru(2,2’-Bipyrazine)32+ by Phenols

Bronner, Catherine and Wenger, Oliver S.. (2012) Kinetic Isotope Effects in Reductive Excited-State Quenching of Ru(2,2’-Bipyrazine)32+ by Phenols. Journal of Physical Chemistry Letters, 3 (1). pp. 70-74.

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Official URL: http://edoc.unibas.ch/48176/

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Electron transfer (ET) from phenol molecules to a photoexcited ruthenium(II) complex was investigated as a function of the para-substituent (R = OCH3, CH3, H, Cl, Br, CN) attached to the phenols. For phenols with electron-donating substituents (R = OCH3, CH3), the rate-determining excited-state deactivation process is ordinary ET. For all other phenols, significant kinetic isotope effects (KIEs) (ranging from 2.91 ± 0.18 for R = Br to 10.18 ± 0.64 for R = CN) are associated with emission quenching, and this is taken as indirect evidence for transfer of a phenolic proton to a peripheral nitrogen atom of a 2,2′-bipyrazine ligand in the course of an overall proton-coupled electron transfer (PCET) reaction. Possible PCET reaction mechanisms for the various phenol/ruthenium couples are discussed. While 4-cyanophenol likely reacts via concerted proton–electron transfer (CPET), a stepwise proton transfer–electron transfer mechanism cannot be excluded in the case of the phenols with R = Br, Cl, and H.
Faculties and Departments:05 Faculty of Science > Departement Chemie > Chemie > Anorganische Chemie (Wenger)
UniBasel Contributors:Wenger, Oliver and Bronner, Catherine
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Chemical Society
Note:Publication type according to Uni Basel Research Database: Journal article
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edoc DOI:
Last Modified:13 Jun 2018 06:42
Deposited On:05 Jan 2017 10:47

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