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Photoredox Properties of Homoleptic d 6 Metal Complexes with the Electron‐Rich 4,4′,5,5′‐Tetramethoxy‐2,2′‐bipyridine Ligand
Author(s) -
Büldt Laura A.,
Prescimone Alessandro,
Neuburger Markus,
Wenger Oliver S.
Publication year - 2015
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201500670
Subject(s) - chemistry , homoleptic , ruthenium , photochemistry , electron transfer , bipyridine , ligand (biochemistry) , ketyl , metal , crystallography , crystal structure , benzophenone , organic chemistry , catalysis , biochemistry , receptor
A synthetic procedure leading to 4,4′,5,5′‐tetramethoxy‐2,2′‐bipyridine [(MeO) 4 bpy] was developed, and the first three metal complexes with this ligand were synthesized. A few ligand precursor compounds, the final ligand, and its homoleptic iron(II) complex were characterized structurally by X‐ray diffraction. The combination of cyclic voltammetry, optical absorption, luminescence, and transient absorption spectroscopy provided detailed insight into the electronic structure of the entire series of homoleptic Fe II , Ru II , and Os II complexes. The ruthenium(II) complex is a more potent photoreductant than the [Ru(bpy) 3 ] 2+ parent compound by approximately 0.4 V as confirmed by 3 MLCT excited‐state quenching experiments with a relatively mild oxidant, 1‐chloro‐4‐nitrobenzene. In the presence of methanesulfonic acid in CH 3 CN, the photoexcited [Ru{(MeO) 4 bpy} 3 ] 2+ complex is able to undergo proton‐coupled electron transfer (PCET) with acetophenone to yield a ketyl radical. Chemically robust and potent photoreductants are of interest for the phototriggering of electron‐transfer reactions, for example, in photoredox catalysis, in dye‐sensitized solar cells, in fundamental studies of (proton‐coupled) electron transfer, or for the generation of solvated electrons.