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Wadman S.H.,Chemical Biology and Organic Chemistry | Van Leeuwen Y.M.,Chemical Biology and Organic Chemistry | Havenith R.W.A.,University Utrecht | Havenith R.W.A.,Radboud University Nijmegen | And 2 more authors.
Organometallics | Year: 2010

We have prepared the dinuclear ruthenium complexes [(R3-tpy) Ru(N^C^N-tpy)Ru(tpy)]3+ (R = H ([5a]3+), CO2Me ([6a]3+), N^C(H)^N-tpy = 4′-(3,5-dipyridylphenyl)-2,2′: 6′,2″-terpyridine, tpy = 2,2′:6′,2″-terpyridine) and [(R3-tpy)Ru(N′^C^N′-tpy)Ru(tpy)]3+ (R = H ([5b]3+), CO2Me ([6b]3+), N′^C(H) ^N′-tpy = 4′-(3,5-di(4-tert-butylpyridyl)phenyl)-2,2′: 6′,2″-terpyridine) in a stepwise manner. The directional nature of the bridging ligand, which is potentially cyclometalating on one side, induces large redox asymmetry in the resulting dinuclear complexes. One-electron oxidation gives rise to a strong metal-to-metal charge transfer transition from the [Ru(tpy2)]2+ moiety to the cycloruthenated group, centered at 1034 nm for [6b]4+. The localized nature of the oxidation processes, the shape of the NIR band, and TD-DFT calculations allow assignment of these systems to localized Robin-Day class II. Exclusive substitution of the terminal tpy ligand on the cyclometalated ruthenium with acid moieties allows selective attachment of the dye to a semiconductor surface, whereby a possible two-step upconversion path is created in dye-sensitized solar cells for the utilization of low-energy photons. © 2010 American Chemical Society. Source

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