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1.
Johansson A Abrahamsson M Magnuson A Huang P Mårtensson J Styring S Hammarström L Sun L Akermark B 《Inorganic chemistry》2003,42(23):7502-7511
The preparation of donor (D)-photosensitizer (S) arrays, consisting of a manganese complex as D and a ruthenium tris(bipyridyl) complex as S has been pursued. Two new ruthenium complexes containing coordinating sites for one (2a) and two manganese ions (3a) were prepared in order to provide models for the donor side of photosystem II in green plants. The manganese coordinating site consists of bridging and terminal phenolate as well as terminal pyridyl ligands. The corresponding ruthenium-manganese complexes, a manganese monomer 2b and dimer 3b, were obtained. For the dimer 3b, our data suggest that intramolecular electron transfer from manganese to photogenerated ruthenium(III) is fast, k(ET) > 5 x 10(7) s(-)(1). 相似文献
2.
Xu Y Eilers G Borgström M Pan J Abrahamsson M Magnuson A Lomoth R Bergquist J Polívka T Sun L Sundström V Styring S Hammarström L Akermark B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(24):7305-7314
To mimic the electron-donor side of photosystem II (PSII), three trinuclear ruthenium complexes (2, 2a, 2b) were synthesized. In these complexes, a mixed-valent dinuclear Ru2(II,III) moiety with one phenoxy and two acetato bridges is covalently linked to a Ru(II) tris-bipyridine photosensitizer. The properties and photoinduced electron/energy transfer of these complexes were studied. The results show that the Ru2(II,III) moieties in the complexes readily undergo reversible one-electron reduction and one-electron oxidation to give the Ru2(II,III) and Ru2(III,III) states, respectively. This could allow for photooxidation of the sensitizer part with an external acceptor and subsequent electron transfer from the dinuclear ruthenium moiety to regenerate the sensitizer. However, all trinuclear ruthenium complexes have a very short excited-state lifetime, in the range of a few nanoseconds to less than 100 ps. Studies by femtosecond time-resolved techniques suggest that a mixture of intramolecular energy and electron transfer between the dinuclear ruthenium moiety and the excited [Ru(bpy)3]2+ photosensitizer is responsible for the short lifetimes. This problem is overcome by anchoring the complexes with ester- or carboxyl-substituted bipyridine ligands (2a, 2b) to nanocrystalline TiO2, and the desired electron transfer from the excited state of the [Ru(bpy)3]2+ moiety to the conduction band of TiO2 followed by intramolecular electron transfer from the dinuclear Ru2(II,III) moiety to photogenerated Ru(III) was observed. The resulting long-lived Ru2(III,III) state decays on the millisecond timescale. 相似文献
3.
Ghanem R Xu Y Pan J Hoffmann T Andersson J Polívka T Pascher T Styring S Sun L Sundström V 《Inorganic chemistry》2002,41(24):6258-6266
We demonstrate a possibility of multistep electron transfer in a supramolecular complex adsorbed on the surface of nanocrystalline TiO(2). The complex mimics the function of the tyrosine(Z)() and chlorophyll unit P(680) in natural photosystem II (PSII). A ruthenium(II) tris(bipyridyl) complex covalently linked to a L-tyrosine ethyl ester through an amide bond was attached to the surface of nanocrystalline TiO(2) via carboxylic acid groups linked to the bpy ligands. Synthesis and characterization of this complex are described. Excitation (450 nm) of the complex promotes an electron to a metal-to-ligand charge-transfer (MLCT) excited state, from which the electron is injected into TiO(2). The photogeneration of Ru(III) is followed by an intramolecular electron transfer from tyrosine to Ru(III), regenerating the photosensitizer Ru(II) and forming the tyrosyl radical. The tyrosyl radical is formed in less than 5 micros with a yield of 15%. This rather low yield is a result of a fast back electron transfer reaction from the nanocrystalline TiO(2) to the photogenerated Ru(III). 相似文献
4.
Stenbj?rn Styring Licheng Sun Leif Hammarstr?m Roman Davydov Mats Almgren Mikael Andersson Helena Berglund Anna B?rje Peter Korall Thomas Norrby Christian Philouze Bj?rn ?kermark 《Journal of Chemical Sciences》1997,109(6):389-396
One attractive way to harvest solar energy is to use the concepts of natural photosynthesis in an artificial system. In green
plant photosynthesis, the solar energy is transformed into usable energy in the form of reduced compounds. The electrons come
from water which is oxidized to molecular oxygen, thereby providing the plants with a never ending supply of reducing equivalents.
In photosystem II, the photosensitizer is a chlorophyll species, P680, which is coupled to a cluster composed of four manganese
ions that catalyses the water oxidation. We have tried to mimic this by the synthesis of a binuclear compound [Ru(bpy)2(Mebpy-Mebpy)MnCl2(H2O)2]Cl2 built on bipyridine ligands containing a Ru(II) moiety (the photosensitizer) and a Mn(II) ion (the donor) linked via a bridging
ligand. In the complex, which is structurally defined by NMR, elemental analysis and electrospray mass spectroscopy, we have
observed, (1) the Mn is sufficiently close (about 13?) to interact with the Ru(II) ion, and (2) intramolecular, photochemically
induced electron transfer from Mn(II) to the photogenerated Ru(III) moiety after a light flash in the presence of an electron
acceptor. We suggest that the synthesis, characterization and observation of intramolecular electron transfer in this novel
Ru-Mn compound is an important step towards artificial photosynthesis. 相似文献
5.
Kajsa G. V. Havelius Johannes Sj?holm Felix M. Ho Fikret Mamedov Stenbj?rn Styring 《Applied magnetic resonance》2010,37(1-4):151-176
The redox-active tyrosine residue (YZ) plays a crucial role in the mechanism of the water oxidation. Metalloradical electron paramagnetic resonance (EPR) signals reflecting the light-induced YZ· in magnetic interaction with the CaMn4-cluster in the particular S-state, YZ·SX intermediates, have been found in intact photosystem II. These so-called split EPR signals are induced by illumination at cryogenic temperatures and provide means to both study the otherwise transient YZ· and to probe the S-states with EPR spectroscopy. The illumination used for signal induction grouped the observed split EPR signals in two categories: (i) YZ in the lower S-states was oxidized by P680+ formed via charge separation, while (ii) YZ in the higher S-states was oxidized by an excited, highly oxidizing Mn species. Applied mechanistic studies of the YZ·SX intermediates in the different S-states are reviewed and compared to investigations in photosystem II at physiological temperature. Addition of methanol induced S-state characteristic changes in the split signals’ formation which reflect changes in the magnetic coupling within the CaMn4-cluster due to methanol binding. The pH titration of the split EPR signals, on the other hand, could probe the proton-coupled electron transfer properties of the YZ oxidation. The apparent pK as found for decreased split signal induction were interpreted in the fate of the phenol proton. 相似文献
6.
Planas N Vigara L Cady C Miró P Huang P Hammarström L Styring S Leidel N Dau H Haumann M Gagliardi L Cramer CJ Llobet A 《Inorganic chemistry》2011,50(21):11134-11142
The geometry and electronic structure of cis-[Ru(II)(bpy)(2)(H(2)O)(2)](2+) and its higher oxidation state species up formally to Ru(VI) have been studied by means of UV-vis, EPR, XAS, and DFT and CASSCF/CASPT2 calculations. DFT calculations of the molecular structures of these species show that, as the oxidation state increases, the Ru-O bond distance decreases, indicating increased degrees of Ru-O multiple bonding. In addition, the O-Ru-O valence bond angle increases as the oxidation state increases. EPR spectroscopy and quantum chemical calculations indicate that low-spin configurations are favored for all oxidation states. Thus, cis-[Ru(IV)(bpy)(2)(OH)(2)](2+) (d(4)) has a singlet ground state and is EPR-silent at low temperatures, while cis-[Ru(V)(bpy)(2)(O)(OH)](2+) (d(3)) has a doublet ground state. XAS spectroscopy of higher oxidation state species and DFT calculations further illuminate the electronic structures of these complexes, particularly with respect to the covalent character of the O-Ru-O fragment. In addition, the photochemical isomerization of cis-[Ru(II)(bpy)(2)(H(2)O)(2)](2+) to its trans-[Ru(II)(bpy)(2)(H(2)O)(2)](2+) isomer has been fully characterized through quantum chemical calculations. The excited-state process is predicted to involve decoordination of one aqua ligand, which leads to a coordinatively unsaturated complex that undergoes structural rearrangement followed by recoordination of water to yield the trans isomer. 相似文献
7.
Berggren G Thapper A Huang P Eriksson L Styring S Anderlund MF 《Inorganic chemistry》2011,50(8):3425-3430
The synthesis, isolation, and characterization of two high-valent manganese dimers with isomeric ligands are reported. The complexes are synthesized and crystallized from solutions of low-valent precursors exposed to tert-butyl hydroperoxide. The crystal structures display centrosymmetric complexes consisting of Mn(2)(IV,IV)(μ-O)(2) cores, with one ligand coordinating to each manganese. The ligands coordinate with the diaminoethane backbone, the carboxylate, and one of the two pyridines, while the second pyridine is noncoordinating. The activity of these complexes, under water oxidation conditions, is discussed in light of a proposed mechanism for water oxidation, in which this type of complexes have been suggested as a key intermediate. 相似文献
8.
Kurz P Berggren G Anderlund MF Styring S 《Dalton transactions (Cambridge, England : 2003)》2007,(38):4258-4261
A set of six multinuclear manganese complexes was screened for the ability to catalyse reactions yielding O(2) under coherent experimental conditions; we identify a much larger number of manganese compounds than previously known that catalyse oxygen formation. 相似文献
9.
Berggren G Huang P Eriksson L Styring S Anderlund MF Thapper A 《Dalton transactions (Cambridge, England : 2003)》2010,39(45):11035-11044
In this work we report the synthesis of two novel manganese complexes, [L1(3)Mn(II)(6)](ClO(4))(6) (1·(ClO(4))(6)) and [L2Mn(II)(2)(μ-OAc)(μ-Cl)](ClO(4))(2) (2·(ClO(4))(2)), where L1(2-) is the 2,2'-(1,3-phenylenebis(methylene))bis((2-(bis(pyridin-2-ylmethyl)amino)ethyl)azanediyl)diacetic acid anion and L2 is N1,N1'-(1,3-phenylenebis(methylene))bis(N2,N2'-bis(pyridin-2-ylmethyl)ethane-1,2-diamine). The ligands Na(2)L1 and L2 are built on the same backbone, L2 only contains nitrogen donors, while two carboxylate arms have been introduced in Na(2)L1. The two complexes have been characterized by single-crystal X-ray diffraction, magnetic susceptibility, EPR spectroscopy, and electrochemistry. X-Ray crystallography revealed that 1 is a manganese(II) hexamer and 2 is a manganese(II) dimer featuring an unprecedented mono-μ-acetato, mono-μ-chlorido bridging motif. The ability of the complexes to catalyse H(2)O(2) disproportionation, thereby acting as models for manganese catalases, has been investigated and compared to the activity of two other related manganese complexes. The introduction of carboxylate donors in the ligands, leading to increased denticity, resulted in a drop in H(2)O(2) disproportionation activity. 相似文献
10.