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- Hammarstrom, L., et al.
(författare)
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A biomimetic approach to artificial photosynthesis : Ru(II)-polypyridine photo-sensitisers linked to tyrosine and manganese electron donors
- 2001
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Ingår i: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy. - 1386-1425 .- 1873-3557. ; 57:11, s. 2145-2160
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Forskningsöversikt (refereegranskat)abstract
- The paper describes recent advances towards the construction of functional rr mics of the oxygen evolving complex in photosystem II (PSII) that are coupled to photoinduced charge separation. Some key principles of PSII and artificial systems for light-induced charge accumulation are discussed. Systems are described where biomimetic electron donors - manganese complexes and tyrosine - have been linked to a Ru(II)-polypyridine photosensitiser. Oxidation of the donors by intramolecular electron transfer from the photo-oxidised Ru(III) complex has been studied using optical flash photolysis and EPR experiments. A step-wise electron transfer Mn-2(III,III) --> tyrosine --> Ru(III) has been demonstrated, in analogy to the reaction on the donor side of PSII Electron transfer from the tyrosine to Ru(III) was coupled to tyrosine deprotonation. This resulted in a large reorganisation energy and thus a slow reaction rate, unless the tyrosine was hydrogen bonded or already deprotonated. A comparison with analogous reactions in PSH is made. Finally, light-induced oxidation of a manganese dimer linked to a Ru(II)-photosensitiser has been observed. Preliminary results suggest the possibility of photo-oxidising manganese dimers in several steps, which is an important advancement towards water oxidation.
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| 2. |
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| 3. |
- Sun, Licheng C., et al.
(författare)
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Towards artificial photosynthesis : ruthenium-manganese chemistry for energy production
- 2001
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Ingår i: Chemical Society Reviews. - : Royal Society of Chemistry (RSC). - 0306-0012 .- 1460-4744. ; 30:1, s. 36-49
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Forskningsöversikt (refereegranskat)abstract
- The synthesis and characterisation of supramolecular model systems mimicking the light reactions on the donor side of Photosystem II (PSII) in green plants have been reviewed. In these systems, manganese complexes and tyrosine are electron donors, modelling the manganese cluster and tyrosine(Z) in PSII. The donors have been covalently linked to a photosensitizer, a ruthenium(ii) tris-bipyridyl complex, that plays the role of the P-680 chlorophylls in PSII. It has been demonstrated that, in the presence of an external electron acceptor in solution, the model systems can undergo an intermolecular electron transfer from the photoexcited state of Ru-II to an acceptor, followed by an intramolecular electron transfer from the coordinated Mn complexes or the tyrosine unit to the photogenerated Ru-III. This leads to regeneration of the Ru-II and oxidation of the Mn complexes or generation of a tyrosine radical. The process closely mimics the primary reaction steps on the donor side of PSII.
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| 4. |
- Sun, LC, et al.
(författare)
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Toward solar energy conversion into fuels: Design and synthesis of ruthenium-manganese supramolecular complexes to mimic the function of photosystem II
- 2003
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Ingår i: ACS Symposium Series. - 0097-6156. ; 852, s. 219-244
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Forskningsöversikt (refereegranskat)abstract
- To mimic the electron donor side of Photosystem II (PSII), a number of supramolecular model complexes have been designed and synthesized. Ruthenium(II) tris-bipyridyl complexes have been used in most cases as photosensitizers, mimicking the function of P-680 in PSII. As electron donors, monomeric and dimeric manganese complexes and tyrosine have been introduced into the supramolecular systems, modelling the Mn cluster and Tyrosinez respectively in PSII For monomeric manganese complexes, di-, tri- and tetradentate ligands have been linked to a Ruthenium(II) trisbipyridyl type complex; and for dimeric manganese complexes hepta-dentate ligands containing pyridines have been used. Some related ligands, where two pyridines have been replaced by phenolate groups have also been synthesized, in order to get ligands that can stabilize manganese complex in high valence states. Photophysical and photochemical studies showed that the electron transfer rate from monomeric Mn complex to photo-generated Ru(III) was low when Mn-Ru distance was long, while the electron transfer rate was enhanced when the Mn-Ru distance was short. However, the excited state of ruthenium complex was quenched if Mn got close to the Ru, leading to a short lifetime. By synthetically inserting a tyrosine unit between Ru and Mn moieties, quenching of the excited state lifetime of Ru was reduced, and the electron transfer from Mn to Ru(III) was very fast although the Mn-Ru distance was long. These supramolecular Ru-Mn systems are closely modelling the electron donor side of PSII both functionally and structurally. The design and synthesis of these model systems are summarized and discussed in this chapter.
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