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Proton-Coupled Electron Transfer Between 4-Cyanophenol and Photoexcited Rhenium(I) Complexes with Different Protonatable Sites

Bronner, Catherine and Wenger, Oliver S.. (2012) Proton-Coupled Electron Transfer Between 4-Cyanophenol and Photoexcited Rhenium(I) Complexes with Different Protonatable Sites. Inorganic Chemistry, 51 (15). pp. 8275-8283.

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Official URL: http://edoc.unibas.ch/48170/

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Abstract

Two rhenium(I) tricarbonyl diimine complexes, one of them with a 2,2′-bipyrazine (bpz) and a pyridine (py) ligand in addition to the carbonyls ([Re(bpz)(CO)3(py)]+), and one tricarbonyl complex with a 2,2′-bipyridine (bpy) and a 1,4-pyrazine (pz) ligand ([Re(bpy)(CO)3(pz)]+) were synthesized, and their photochemistry with 4-cyanophenol in acetonitrile solution was explored. Metal-to-ligand charge transfer (MLCT) excitation occurs toward the protonatable bpz ligand in the [Re(bpz)(CO)3(py)]+ complex while in the [Re(bpy)(CO)3(pz)]+ complex the same type of excitation promotes an electron away from the protonatable pz ligand. This study aimed to explore how this difference in electronic excited-state structure affects the rates and the reaction mechanism for photoinduced proton-coupled electron transfer (PCET) between 4-cyanophenol and the two rhenium(I) complexes. Transient absorption spectroscopy provides clear evidence for PCET reaction products, and significant H/D kinetic isotope effects are observed in some of the luminescence quenching experiments. Concerted proton–electron transfer is likely to play an important role in both cases, but a reaction sequence of proton transfer and electron transfer steps cannot be fully excluded for the 4-cyanophenol/[Re(bpz)(CO)3(py)]+ reaction couple. Interestingly, the rate constants for bimolecular excited-state quenching are on the same order of magnitude for both rhenium(I) complexes.
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
ISSN:0020-1669
Note:Publication type according to Uni Basel Research Database: Journal article -- The final publication is available at American Chemical Society, see DOI link
Language:English
Identification Number:
Last Modified:13 Jun 2018 07:09
Deposited On:05 Jan 2017 10:17

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