- Bridging Efficiency within Multinuclear Homogeneous Catalysts in the Photocatalytic Reduction of Carbon Dioxide
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A trinuclear complex consisting of one [Ru(dmb)3]2+ (dmb=4,4′-dimethyl-2,2′-bipyridine) (Ru) and two [Re(dmb)(CO)3Cl] (Re) building blocks, [Re(CO)3Cl(dmb-dmb)Ru(dmb)(dmb-dmb)Re(CO)3Cl](PF6)2 (Re-Ru-Re), is presented. Photophysical properties of Re-Ru-Re and the individual components with different or no covalent linkages are thoroughly investigated and compared. To elucidate the role of the single covalent bonds, photocatalytic reduction of CO2 is performed with the trinuclear complex and a series of model systems featuring systematic absence of linkages between the metal centers. Photoluminescence spectra and quantum yields reveal efficient energy transfer from the excited state of Re to Ru if these fragments are covalently linked. Moreover, intramolecular electron transfer from the one-electron reduced species of Ru to Re occurs if there is covalent bonding, leading to a higher photostability and thus the highest turnover number in photocatalytic CO2 reduction of 199 for the trinuclear complex Re-Ru-Re within the systems under investigation. Optimized experimental conditions reveal the highest turnover number (315) reported to date for ReI/RuII-based homogeneous catalysts in photocatalytic CO2 reduction.
- Meister, Simon,Reithmeier, Richard O.,Ogrodnik, Alexander,Rieger, Bernhard
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- Electrochemistry, Spectroelectrochemistry, and Photochemistry of a Series of New Covalently Linked Tris(2,2'-bipyridine)ruthenium(II)/Diquat Complexes
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A method for preparing covalently linked photosensitizer / electron-acceptor complexes using a novel dimer of 4,4'-dimethyl-2,2'-bipyridine has been found.N,N'-Dialkylation of one end of the dimer results in a "diquat"-modified ligand which can be bound to Ru(II) in combination with other substituted or unsubstituted bipyridines.A series of tris(bipyridine)ruthenium/diquat complexes was prepared in which the properties of both the diquat electron acceptor and the ruthenium photosensitizer were varied.The effect of the detailed structure of these linked systems on their electrochemical, spectroelectrochemical, and photophysical properties was investigated.
- Elliott, C. Michael,Freitag, Ruth A.,Blaney, David D.
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- Binuclear, ruthenium - manganese complexes as simple artificial models, for photosystem II in green plants
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As part of a project aimed at developing models for photosystem II (PSII) in green plants, we have prepared a series of model compounds (7, 8, and 13). In these compounds, a photosensitizer, ruthenium(II) tris(bipyridyl) complex (to mimic the function of P680 in PSII), was covalently linked to a manganese(II) ion through different bridging ligands. The structures of the compounds were characterized by electron paramagnetic resonance measurements and electrospray ionization mass spectrometry. The interaction between the ruthenium and manganese moleties within the complex was probed by steady- state and time-resolved emission measurements. When the binuclear complexes are exposed to flash photolysis in the presence of an electron acceptor such as methylviologen (MV2+), it could be shown that after the initial electron transfer from the excited state of Ru(II) in compound 7, forming Ru(III) and MV+. , an intramolecular electron transfer from coordinated Mn(II) to the photogenerated Ru(III) occurred with a first-order rate constant of 1.8 x 105 s-1, regenerating Ru(II). This is believed to be the first supramolecular system where a manganese complex has been used as an electron donor to a photo-oxidized photosensitizer. Possible extensions to develop the manganese donor, and thus to approach the function of reaction center in PSII, are indicated.
- Sun, Licheng,Berglund, Helena,Davydov, Roman,Norrby, Thomas,Hammarstr?m, Leif,Korall, Peter,B?rje, Anna,Philouze, Christian,Berg, Katja,Tran, Anh,Andersson, Michael,Stenhagen, Gunnar,M?rtensson, Jerker,Almgren, Mats,Styring, Stenbj?rn,?kermark, Bj?rn
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p. 6996 - 7004
(2007/10/03)
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- Intramolecular Energy Transfer in Covalently Linked Polypyridine Ruthenium(II)/Osmium(II) Binuclear Complexes. Ru(II)(bpy)2Mebpy(CH2)n-MebpyOs(II)(bpy)2 (n=2, 3, 5, and 7)
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A novel series of polymethylene-linked heterobinuclear complexes of polypyridine ruthenium(II)/osmium(II) complex Ru(II)(bpy)2Mebpy-(CH2)n-MebpyOs(II)(bpy)2(bpy=2,2'-bipyridine and N=2, 3, 5, and 7), 1, was prepared.The photophysical behavior was examined in various solvents.The emission spectra of 1 (excitation wavelength: 455 nm) showed a nearly complete quenching of Ru(II) -> ?*(bpy) metal-to-ligand charge transfer (MLCT) emission and the enhancement of Os(II) -> ?*(bpy) MLCT emission.The luminescence lifetime measurements by a time-correlated single photon-counting method provided evidence that intramolecular energy transfer is a significant pathway for the observed emission quenching.The rate constants of the intramolecular energy transfer in ethanol are 5.3 * 108, 3.3 * 108, 1.3 * 108, and 1.0 * 108 s-1 for 1 (n=2, 3, 5, and 7), respectively.They were found to be proportional to the inverse sixth power on the center-to-center distance of the two complexes.The mechanisms is discussed in terms of the Foerster (a dipole-dipole interaction) mechanism.
- Furue, Masaoki,Yoshidzumi, Toshiyuki,Kinoshita, Shuichi,Kushida, Takashi,Nozakura, Shun-ichi,Kamachi, Mikiharu
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p. 1632 - 1640
(2007/10/02)
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- Synthesis and Luminescence Properties of Di- and Tri-methylene Linked Tris(2,2'-bipyridine)ruthenium(II) Complex Dimers. Ground-Excited State Interaction
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Di- and tri-methylene-linked Ru(bpy)3(2+) complexes 2 were synthesized.The luminescence properties of 2 were compared with those of its component monomer.In the excited 2 systems, the intermolecular interaction leading to the enhanced quenching or the formation of a new triplet excimer was not observed.
- Furue, Masaoki,Kuroda, Noritaka,Nozakura, Shun-ichi
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p. 1209 - 1212
(2007/10/02)
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