jp300090n_si_001.pdf (296.84 kB)
Hydrogen-Bond Strengthening upon Photoinduced Electron Transfer in Ruthenium–Anthraquinone Dyads Interacting with Hexafluoroisopropanol or Water
journal contribution
posted on 2012-04-05, 00:00 authored by Jihane Hankache, David Hanss, Oliver S. WengerQuinones 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.
History
Usage metrics
Categories
Keywords
anthraquinone reductionproton motionPCETelectron transferPhotoinduced Electron Transferanthraquinone carbonyl functionselectron acceptorshydroxyl grouphexafluoroisopropanolelectron transfer processdichloromethane solutionsquinone reduction pointsdonorhydrogen bondsphotoinduced intramolecularintramolecular electron transferphotoinduced reactionproton density1 order
Licence
Exports
RefWorks
BibTeX
Ref. manager
Endnote
DataCite
NLM
DC