« Photostable Polynuclear Ruthenium(II) Photosensitizers Competent for Dehalogenation Photoredox Catalysis at 590 nm»
Simon Cerfontaine, Sara A. M. Wehlin, Benjamin Elias *, and Ludovic Troian-Gautier*, J. Am. Chem. Soc. 2020, 142, 5549−5555
The increased reactivity of sensitizers upon light excitation has contributed to the drastic development of the field of photoredox catalysis, where they have been harnessed to perform challenging organic transformations, difficult to achieve without the use of photoactive catalysts. Ruthenium(II) polypyridyl sensitizers represent attractive candidates as they absorb visible light typically with molar absorption coefficients greater than 10000 M–1cm–1 and exhibit relatively long-lived excited states.
In our recent study published in the Journal of the American Chemical Society and performed in close collaboration with Dr. Ludovic Troian-Gautier (ULB), we have reported on the use of dinuclear, trinuclear, and quadrinuclear ruthenium(II) 2,2′-bipyridine based photosensitizers for the photo-mediated dehalogenation reaction of 4-bromobenzyl-2-chloro-2-phenylacetate. The performances were compared to the parent compound [Ru(bpy)3]2+. Higher nuclearity photosensitizers produced dehalogenation yields greater than 90% with orange light in 7 hours, whereas after 72 hours, yields of 49% were obtained with [Ru(bpy)3]2+. Three main factors were shown to lead to increased yields: (i) the red-shifted absorbance of polynuclear photosensitizers, (ii) the more favourable driving force for electron transfer, and (iii) the higher photostability of polynuclear species. Collectively, these results highlight the potential advantages of using polynuclear photosensitizers in phototriggered redox catalysis reactions.
J. Am. Chem. Soc. 2020, 142, 12, 5549–5555
Publication Date:March 8, 2020