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Hydrogen-Bond Strengthening upon Photoinduced Electron Transfer in Ruthenium-Anthraquinone Dyads Interacting with Hexafluoroisopropanol or Water

Hankache, Jihane and Hanss, David and Wenger, Oliver S.. (2012) Hydrogen-Bond Strengthening upon Photoinduced Electron Transfer in Ruthenium-Anthraquinone Dyads Interacting with Hexafluoroisopropanol or Water. Journal of Physical Chemistry A, 116 (13). pp. 3347-3358.

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Official URL: http://edoc.unibas.ch/48175/

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Abstract

Quinones play a key role as primary electron acceptors in natural photosynthesis, and their reduction is known to be facilitated by hydrogen-bond donors or protonation. In this study, the influence of hydrogen-bond donating solvents on the thermodynamics and kinetics of intramolecular electron transfer between Ru(bpy)32+ (bpy = 2,2′-bipyridine) and 9,10-anthraquinone redox partners linked together via one up to three p-xylene units was investigated. Addition of relatively small amounts of hexafluoroisopropanol to dichloromethane solutions of these rigid rodlike donor–bridge–acceptor molecules is found to accelerate intramolecular Ru(bpy)32+-to-anthraquinone electron transfer substantially because anthraquinone reduction occurs more easily in the presence of the strong hydrogen-bond donor. Similarly, the rates for intramolecular electron transfer are significantly higher in acetonitrile/water mixtures than in dry acetonitrile. In dichloromethane, an increase in the association constant between hexafluoroisopropanol and anthraquinone by more than 1 order of magnitude following quinone reduction points to a significant strengthening of the hydrogen bonds between the hydroxyl group of hexafluoroisopropanol and the anthraquinone carbonyl functions. The photoinduced intramolecular long-range electron transfer process thus appears to be followed by proton motion; hence the overall photoinduced reaction may be considered a variant of stepwise proton-coupled electron transfer (PCET) in which substantial proton density (rather than a full proton) is transferred after the electron transfer has occurred.
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
ISSN:1089-5639
e-ISSN:1520-5215
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 07:12
Deposited On:05 Jan 2017 10:43

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