51
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Baffert C, Dumas S, Chauvin J, Leprêtre JC, Collomb MN, Deronzier A. Photoinduced oxidation of [Mn(L)3]2+and [Mn2O2(L)4]3+ (L = 2,2′-bipyridine and 4,4′-dimethyl-2,2′-bipyridine) with the [Ru(bpy)3]2+/-aryl diazonium salt system. Phys Chem Chem Phys 2005. [DOI: 10.1039/b411365a] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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52
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Pan J, Xu Y, Benkö G, Feyziyev Y, Styring S, Sun L, Åkermark B, Polívka T, Sundström V. Stepwise Charge Separation from a Ruthenium−Tyrosine Complex to a Nanocrystalline TiO2 Film. J Phys Chem B 2004. [DOI: 10.1021/jp049449v] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jingxi Pan
- Department of Chemical Physics, Lund University, Box 124, S-22100 Lund, Sweden, Department of Organic Chemistry, Stockholm University, S-10691 Stockholm, Sweden, Department of Biochemistry, Lund University, Box 124, S-22100 Lund, Sweden, and Molecular Biomimetics, Uppsala University, Villavagen 6, S-75236 Uppsala, Sweden
| | - Yunhua Xu
- Department of Chemical Physics, Lund University, Box 124, S-22100 Lund, Sweden, Department of Organic Chemistry, Stockholm University, S-10691 Stockholm, Sweden, Department of Biochemistry, Lund University, Box 124, S-22100 Lund, Sweden, and Molecular Biomimetics, Uppsala University, Villavagen 6, S-75236 Uppsala, Sweden
| | - Gabor Benkö
- Department of Chemical Physics, Lund University, Box 124, S-22100 Lund, Sweden, Department of Organic Chemistry, Stockholm University, S-10691 Stockholm, Sweden, Department of Biochemistry, Lund University, Box 124, S-22100 Lund, Sweden, and Molecular Biomimetics, Uppsala University, Villavagen 6, S-75236 Uppsala, Sweden
| | - Yashar Feyziyev
- Department of Chemical Physics, Lund University, Box 124, S-22100 Lund, Sweden, Department of Organic Chemistry, Stockholm University, S-10691 Stockholm, Sweden, Department of Biochemistry, Lund University, Box 124, S-22100 Lund, Sweden, and Molecular Biomimetics, Uppsala University, Villavagen 6, S-75236 Uppsala, Sweden
| | - Stenbjörn Styring
- Department of Chemical Physics, Lund University, Box 124, S-22100 Lund, Sweden, Department of Organic Chemistry, Stockholm University, S-10691 Stockholm, Sweden, Department of Biochemistry, Lund University, Box 124, S-22100 Lund, Sweden, and Molecular Biomimetics, Uppsala University, Villavagen 6, S-75236 Uppsala, Sweden
| | - Licheng Sun
- Department of Chemical Physics, Lund University, Box 124, S-22100 Lund, Sweden, Department of Organic Chemistry, Stockholm University, S-10691 Stockholm, Sweden, Department of Biochemistry, Lund University, Box 124, S-22100 Lund, Sweden, and Molecular Biomimetics, Uppsala University, Villavagen 6, S-75236 Uppsala, Sweden
| | - Björn Åkermark
- Department of Chemical Physics, Lund University, Box 124, S-22100 Lund, Sweden, Department of Organic Chemistry, Stockholm University, S-10691 Stockholm, Sweden, Department of Biochemistry, Lund University, Box 124, S-22100 Lund, Sweden, and Molecular Biomimetics, Uppsala University, Villavagen 6, S-75236 Uppsala, Sweden
| | - Tomáš Polívka
- Department of Chemical Physics, Lund University, Box 124, S-22100 Lund, Sweden, Department of Organic Chemistry, Stockholm University, S-10691 Stockholm, Sweden, Department of Biochemistry, Lund University, Box 124, S-22100 Lund, Sweden, and Molecular Biomimetics, Uppsala University, Villavagen 6, S-75236 Uppsala, Sweden
| | - Villy Sundström
- Department of Chemical Physics, Lund University, Box 124, S-22100 Lund, Sweden, Department of Organic Chemistry, Stockholm University, S-10691 Stockholm, Sweden, Department of Biochemistry, Lund University, Box 124, S-22100 Lund, Sweden, and Molecular Biomimetics, Uppsala University, Villavagen 6, S-75236 Uppsala, Sweden
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53
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Johansson O, Wolpher H, Borgström M, Hammarström L, Bergquist J, Sun L, Akermark B. Intramolecular charge separation in a hydrogen bonded tyrosine–ruthenium(ii)–naphthalene diimide triad. Chem Commun (Camb) 2004:194-5. [PMID: 14737545 DOI: 10.1039/b308101j] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Long-lived charge-separated states in the ns to [micro sign]s range were observed upon laser flash excitation of a donor-chromophore-acceptor triad based on tris(bipyridine) ruthenium(ii) as photo-sensitizer, naphthalene diimide as acceptor, and a hydrogen bonded phenol as donor.
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Affiliation(s)
- Olof Johansson
- Department of Physical Chemistry, Uppsala University, P.O. Box 579, 751 23 Uppsala, Sweden
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54
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Li H, Shi F, Gao Y, Zhang R, Peng X, Sun L. Synthesis and Characterisation of a High Valent Dinuclear Mn(III,III) Complex of a Triphenolate Ligand [N 4O 3] 3- with two Extra Functional Groups. JOURNAL OF CHEMICAL RESEARCH 2004. [DOI: 10.3184/030823404323000800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A new high valent complex [Mn2(III,III)L(μ-OAc)2]·PF67 was prepared, where L was the tri-anion of 2,6-Bis {[(2-hydroxy-5- tert-butylbenzyl)(pyridyl-2-methyl)amino]methyl}-4-methylphenol which contained two additional phenolate groups and two tert-butyl groups compared to its parent [Mn2(II,II)(bpmp)(μ-OAc)2]·PF6. These improvements narrowed the disparity between the new model and (Mn)4 cluster (OEC in nature).
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Affiliation(s)
- Hongyang Li
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
| | - Feng Shi
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
| | - Yan Gao
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
| | - Rong Zhang
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
| | - Xiaojun Peng
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
| | - Licheng Sun
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
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55
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Polyakov NE, Taraban MB, Leshina TV. Photo-CIDNP Study of the Interaction of Tyrosine with Nifedipine. An Attempt to Model the Binding Between Calcium Receptor and Calcium Antagonist Nifedipine¶. Photochem Photobiol 2004; 80:565-71. [PMID: 15623344 DOI: 10.1562/0031-8655(2004)080<0565:psotio>2.0.co;2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
This article proposes a new approach to the modeling of the molecular-level mechanism of ligand-receptor interaction for Ca2+ receptor binding site. Chemically induced dynamic nuclear polarization (CIDNP) technique has been used to unravel fine details of the reaction in the model system composed of one of the known Ca2+ antagonist drugs, nifedipine (NF), and isolated amino acid residuals (e.g. tyrosine [Tyr]) of Ca2+ receptor binding site. It has been conclusively demonstrated that the reaction between NF and Tyr resulting in the oxidation product--nitroso form of NF--obeys the radical mechanism. CIDNP data in combination with the results of mathematical modeling of the structures of ligand-receptor complexes have allowed to propose the mechanism of the interaction of NF with Ca2+ receptor binding site.
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56
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Syntheses and characterization of some chloro, methoxy, and mercapto derivatives of [Ru(η2-2,2′-bipyridine)3]2+2PF6−: crystal and molecular structures of [Ru(η2-2,2′-bipyridine)2(η2-4,4′-(X)2-2,2′-bipyridine)]2+2PF6− (X=Cl, OCH3). Inorganica Chim Acta 2003. [DOI: 10.1016/s0020-1693(02)01485-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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57
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Chiavarino B, Crestoni M, Fornarini S. Gas phase regioselectivity in the deprotonation of p-cresol radical cation. Chem Phys Lett 2003. [DOI: 10.1016/s0009-2614(03)00398-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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58
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A peptide approach to covalently linked [Ru(bipy)3]2+–ferrocene and [Ru(bipy)3]2+–tyrosine conjugates. Inorganica Chim Acta 2003. [DOI: 10.1016/s0020-1693(02)01339-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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59
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Nagata T, Kikuzawa Y, Osuka A. Synthesis and photoreaction of a porphyrin–Co(III)-complex linked molecule. Inorganica Chim Acta 2003. [DOI: 10.1016/s0020-1693(02)01137-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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60
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Huang P, Magnuson A, Lomoth R, Abrahamsson M, Tamm M, Sun L, van Rotterdam B, Park J, Hammarström L, Akermark B, Styring S. Photo-induced oxidation of a dinuclear Mn(2)(II,II) complex to the Mn(2)(III,IV) state by inter- and intramolecular electron transfer to Ru(III)tris-bipyridine. J Inorg Biochem 2002; 91:159-72. [PMID: 12121773 DOI: 10.1016/s0162-0134(02)00394-x] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
To model the structural and functional parts of the water oxidizing complex in Photosystem II, a dimeric manganese(II,II) complex (1) was linked to a ruthenium(II)tris-bipyridine (Ru(II)(bpy)(3)) complex via a substituted L-tyrosine, to form the trinuclear complex 2 [J. Inorg. Biochem. 78 (2000) 15]. Flash photolysis of 1 and Ru(II)(bpy)(3) in aqueous solution, in the presence of an electron acceptor, resulted in the stepwise extraction of three electrons by Ru(III)(bpy)(3) from the Mn(2)(II,II) dimer, which then attained the Mn(2)(III,IV) oxidation state. In a similar experiment with compound 2, the dinuclear Mn complex reduced the photo-oxidized Ru moiety via intramolecular electron transfer on each photochemical event. From EPR it was seen that 2 also reached the Mn(2)(III,IV) state. Our data indicate that oxidation from the Mn(2)(II,II) state proceeds stepwise via intermediate formation of Mn(2)(II,III) and Mn(2)(III,III). In the presence of water, cyclic voltammetry showed an additional anodic peak beyond Mn(2)(II,III/III,III) oxidation which was significantly lower than in neat acetonitrile. Assuming that this peak is due to oxidation to Mn(2)(III,IV), this suggests that water is essential for the formation of the Mn(2)(III,IV) oxidation state. Compound 2 is a structural mimic of the water oxidizing complex, in that it links a Mn complex via a tyrosine to a highly oxidizing photosensitizer. Complex 2 also mimics mechanistic aspects of Photosystem II, in that the electron transfer to the photosensitizer is fast and results in several electron extractions from the Mn moiety.
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Affiliation(s)
- P Huang
- Department of Biochemistry, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, S-221 00 Lund, Sweden
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61
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He J, Benkö G, Korodi F, Polívka T, Lomoth R, Akermark B, Sun L, Hagfeldt A, Sundström V. Modified phthalocyanines for efficient near-IR sensitization of nanostructured TiO(2) electrode. J Am Chem Soc 2002; 124:4922-32. [PMID: 11971744 DOI: 10.1021/ja0178012] [Citation(s) in RCA: 373] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A zinc phthalocyanine with tyrosine substituents (ZnPcTyr), modified for efficient far-red/near-IR performance in dye-sensitized nanostructured TiO(2) solar cells, and its reference, glycine-substituted zinc phthalocyanine (ZnPcGly), were synthesized and characterized. The compounds were studied spectroscopically, electrochemically, and photoelectrochemically. Incorporating tyrosine groups into phthalocyanine makes the dye ethanol-soluble and reduces surface aggregation as a result of steric effects. The performance of a solar cell based on ZnPcTyr is much better than that based on ZnPcGly. Addition of 3alpha,7alpha-dihydroxy-5beta-cholic acid (cheno) and 4-tert-butylpyridine (TBP) to the dye solution when preparing a dye-sensitized TiO(2) electrode diminishes significantly the surface aggregation and, therefore, improves the performance of solar cells based on these phthalocyanines. The highest monochromatic incident photo-to-current conversion efficiency (IPCE) of approximately 24% at 690 nm and an overall conversion efficiency (eta) of 0.54% were achieved for a cell based on a ZnPcTyr-sensitized TiO(2) electrode. Addition of TBP in the electrolyte decreases the IPCE and eta considerably, although it increases the open-circuit photovoltage. Time-resolved transient absorption measurements of interfacial electron-transfer kinetics in a ZnPcTyr-sensitized nanostructured TiO(2) thin film show that electron injection from the excited state of the dye into the conduction band of TiO(2) is completed in approximately 500 fs and that more than half of the injected electrons recombines with the oxidized dye molecules in approximately 300 ps. In addition to surface aggregation, the very fast electron recombination is most likely responsible for the low performance of the solar cell based on ZnPcTyr.
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Affiliation(s)
- Jianjun He
- Department of Chemical Physics, Lund University, S-221 00 Lund, Sweden
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62
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Fang Y, Liu L, Feng Y, Li XS, Guo QX. Effects of Hydrogen Bonding to Amines on the Phenol/Phenoxyl Radical Oxidation. J Phys Chem A 2002. [DOI: 10.1021/jp014425z] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ying Fang
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Lei Liu
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Yong Feng
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Xiao-Song Li
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Qing-Xiang Guo
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, P. R. China
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63
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Abrahamsson MLA, Baudin HB, Tran A, Philouze C, Berg KE, Raymond-Johansson MK, Sun L, Akermark B, Styring S, Hammarstrom L. Ruthenium-manganese complexes for artificial photosynthesis: factors controlling intramolecular electron transfer and excited-state quenching reactions. Inorg Chem 2002; 41:1534-44. [PMID: 11896722 DOI: 10.1021/ic0107227] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Continuing our work toward a system mimicking the electron-transfer steps from manganese to P(680)(+) 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 x 10(5)-2 x 10(7) s(-1), and we have investigated different factors that are responsible for the variation. The reorganization energies determined experimentally (lambda = 1.5-2.0 eV) are larger than expected for solvent reorganization in complexes of similar size in polar solvents (typically lambda approximately 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.
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Affiliation(s)
- Malin L A Abrahamsson
- Department of Physical Chemistry, Uppsala University, Box 532, S-751 21 Uppsala, Sweden
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64
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Fiammengo R, Crego-Calama M, Reinhoudt DN. Synthetic self-assembled models with biomimetic functions. Curr Opin Chem Biol 2001; 5:660-73. [PMID: 11738176 DOI: 10.1016/s1367-5931(01)00263-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Self-assembly can be considered a powerful tool in the hand of chemists for the understanding, modeling and mimicking of biological systems. The possibility of reproducing biological functions in synthetic systems obtained by self-assembly is envisioned as a modest but very important step towards the understanding of the mystery of life and its emergence on Earth.
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Affiliation(s)
- R Fiammengo
- Laboratory of Supramolecular Chemistry and Technology, MESA+ Research Institute, University of Twente, PO Box 217, 7500 AE, Enschede, The Netherlands
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65
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Omura Y, Taruno Y, Irisa Y, Morimoto M, Saimoto H, Shigemasa Y. Regioselective Mannich reaction of phenolic compounds and its application to the synthesis of new chitosan derivatives. Tetrahedron Lett 2001. [DOI: 10.1016/s0040-4039(01)01491-5] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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66
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Hammarström L, Sun L, Akermark B, Styring S. A biomimetic approach to artificial photosynthesis: Ru(II)-polypyridine photo-sensitisers linked to tyrosine and manganese electron donors. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2001; 57:2145-2160. [PMID: 11603836 DOI: 10.1016/s1386-1425(01)00491-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The paper describes recent advances towards the construction of functional mimics 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(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 PSII 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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Affiliation(s)
- L Hammarström
- Department of Physical Chemistry, Uppsala University, Sweden.
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67
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Hammarström L, Sun L, Åkermark B, Styring S. Mimicking photosystem II reactions in artificial photosynthesis: Ru(II)-polypyridine photosensitisers linked to tyrosine and manganese electron donors. Catal Today 2000. [DOI: 10.1016/s0920-5861(00)00242-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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68
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Sun L, Raymond MK, Magnuson A, LeGourriérec D, Tamm M, Abrahamsson M, Kenéz PH, Mårtensson J, Stenhagen G, Hammarström L, Styring S, Akermark B. Towards an artificial model for Photosystem II: a manganese(II,II) dimer covalently linked to ruthenium(II) tris-bipyridine via a tyrosine derivative. J Inorg Biochem 2000; 78:15-22. [PMID: 10714701 DOI: 10.1016/s0162-0134(99)00200-7] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
In order to model the individual electron transfer steps from the manganese cluster to the photooxidized sensitizer P680+ in Photosystem II (PS II) in green plants, the supramolecular complex 4 has been synthesized. In this complex, a ruthenium(II) tris-bipyridine type photosensitizer has been linked to a manganese(II) dimer via a substituted L-tyrosine, which bridges the manganese ions. The trinuclear complex 4 was characterized by electron paramagnetic resonance (EPR) and electrospray ionization mass spectrometry (ESI-MS). The excited state lifetime of the ruthenium tris-bipyridine moiety in 4 was found to be about 110 ns in acetonitrile. Using flash photolysis in the presence of an electron acceptor (methylviologen), it was demonstrated that in the supramolecular complex 4 an electron was transferred from the excited state of the ruthenium tris-bipyridine moiety to methylviologen, forming a methylviologen radical and a ruthenium(III) tris-bipyridine moiety. Next, the Ru(III) species retrieved the electron from the manganese(II/II) dimer in an intramolecular electron transfer reaction with a rate constant kET > 1.0 x 10(7) s(-1), generating a manganese(II/III) oxidation state and regenerating the ruthenium(II) photosensitizer. This is the first example of intramolecular electron transfer in a supramolecular complex, in which a manganese dimer is covalently linked to a photosensitizer via a tyrosine unit, in a process which mimics the electron transfer on the donor side of PS II.
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Affiliation(s)
- L Sun
- Department of Chemistry, Organic Chemistry, Royal Institute of Technology KTH, Stockholm, Sweden
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69
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Burdinski D, Bothe E, Wieghardt K. Synthesis and characterization of tris(bipyridyl)ruthenium(II)-modified mono-, di-, and trinuclear manganese complexes as electron-transfer models for photosystem II. Inorg Chem 2000; 39:105-16. [PMID: 11229016 DOI: 10.1021/ic990755a] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
With the aim of modeling the arrangement of redox-active and photoactive components along the electron-transfer pathway of photosystem II, tetra- to nonanuclear transition metal complexes have been synthesized, comprising one, two, or three manganese ions, oxidizable phenolates, and tris(2,2'-bipyridyl)ruthenium(II)-type units as photosensitizers. These model complexes are considered to be mononuclear ([LnMn](PF6)m), dinuclear ([L1aMnIV2(mu-O)2](PF6)6), or trinuclear ([LnMnIIMnIIMnIILn](PF6)12) with respect to the number of manganese centers present. Electronic coupling between the manganese ions is strongly antiferromagnetic in the case of the di(mu-oxo)-dimanganese compound [L1aMnIV2(mu-O)2](PF6)6, where the "ligand" [H2L1a]4+ consists of two tris(bipyridyl)ruthenium(II)-type units covalentely bound to a bismacrocyclic Me2dtne backbone to which the manganese ions are coordinated via an additional phenolate oxygen (Me2dtne = 1,2-bis(4-methyl-1,4,7-triazacyclononyl)ethane). Weak antiferromagnetic coupling is observed in compounds [LnMnIIMnIIMnIILn](PF6)12, where the three metals are in a linear arrangement (face-sharing octahedral). They are bridged by three phenolate oxygens of each of the deprotonated "ligands" [H3Ln]6+, respectively. Each ligand [H3Ln]6+ (n = 1, 2) consists of a tacn ring with three pendent arm phenols which are each bound to a tris(bipyridyl)ruthenium(II)-type unit (tacn = 1,4,7-triazacyclononane). In these compounds several electron-transfer steps were detected by electrochemical methods which are assigned to different redox processes located at individual electrochemically active components (Mn, Ru, bipyridyl, phenolate). For example, in the "mononuclear" compounds [LnMn](PF6)m (n = 1 or 2) Mn(II), Mn(III), and Mn(IV) are accessible and three Ru(II) centers are reversibly oxidized to Ru(III), and in addition, the coordinated phenolate can be oxidized to a highly reactive, coordinated phenoxyl radical. In several cases very slow heterogeneous electron-transfer rates were observed for redox processes involving the manganese centers.
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Affiliation(s)
- D Burdinski
- Max-Planck Institut für Strahlenchemie, Stiftstrasse 34-36, D-45470 Mülheim, Germany
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