Ruthenium−Manganese Complexes for Artificial Photosynthesis:  Factors Controlling Intramolecular Electron Transfer and Excited-State Quenching Reactions

Ruthenium−Manganese Complexes for Artificial Photosynthesis:  Factors Controlling Intramolecular Electron Transfer and Excited-State Quenching Reactions

Continuing our work toward a system mimicking the electron-transfer steps from manganese to P680 + in photosystem II (PS II), we report a series of ruthenium(II)−manganese(II) complexes that display intramolecular electron transfer from manganese(II) to photooxidized ruthenium(III). The electron-tra...

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Published in:Inorganic chemistry Vol. 41; no. 6; pp. 1534 - 1544
Main Authors: Abrahamsson, Malin L. A, Baudin, Helena Berglund, Tran, Anh, Philouze, Christian, Berg, Katja E, Raymond-Johansson, Mary Katherine, Sun, Licheng, Åkermark, Björn, Styring, Stenbjörn, Hammarström, Leif
Format: Journal Article
Language:English
Published: United States American Chemical Society 25-03-2002
Subjects:
acceptor molecules
Biologi
Biological Sciences
Chemistry
delocalization
Ecology
Ekologi
evolution
Fysikalisk kemi
Kemi
ligand
NATURAL SCIENCES
NATURVETENSKAP
oxygen-evolving complex
photosystem-ii
Physical chemistry
ray-absorption spectroscopy
s-0 state
water-oxidation
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Summary:Continuing our work toward a system mimicking the electron-transfer steps from manganese to P680 + in photosystem II (PS II), we report a series of ruthenium(II)−manganese(II) complexes that display intramolecular electron transfer from manganese(II) to photooxidized ruthenium(III). The electron-transfer rate constant (k ET) values span a large range, 1 × 105−2 × 107 s-1, and we have investigated different factors that are responsible for the variation. The reorganization energies determined experimentally (λ = 1.5−2.0 eV) are larger than expected for solvent reorganization in complexes of similar size in polar solvents (typically λ ≈ 1.0 eV). This result indicates that the inner reorganization energy is relatively large and, consequently, that at moderate driving force values manganese complexes are not fast donors. Both the type of manganese ligand and the link between the two metals are shown to be of great importance to the electron-transfer rate. In contrast, we show that the quenching of the excited state of the ruthenium(II) moiety by manganese(II) in this series of complexes mainly depends on the distance between the metals. However, by synthetically modifying the sensitizer so that the lowest metal-to-ligand charge transfer state was localized on the nonbridging ruthenium(II) ligands, we could reduce the quenching rate constant in one complex by a factor of 700 without changing the bridging ligand. Still, the manganese(II)−ruthenium(III) electron-transfer rate constant was not reduced. Consequently, the modification resulted in a complex with very favorable properties.
Bibliography:istex:2C1359456186963038B9FA37F37EFDAA065B21B7
ark:/67375/TPS-R0761D8L-J
ObjectType-Article-1
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ISSN:0020-1669
1520-510X
1520-510X
DOI:10.1021/ic0107227