| 1. |
- Li, Cheng, et al.
(författare)
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Photochemical hydrogen production catalyzed by polypyridyl ruthenium-cobaloxime heterobinuclear complexes with different bridges
- 2009
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Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X .- 1872-8561. ; 694:17, s. 2814-2819
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Tidskriftsartikel (refereegranskat)abstract
- Two heterobinuclear complexes [(bpy)(2)Ru(bpy-4-CH3,4'-CONH(4-py)Co(dmgBF(2))(2)(OH2)](PF6)(2) (1, dmgBF(2) = (difluoroboryl) dimethylglyoximato) and [(bpy)(2)Ru(bpy-4-CH3,4'-CONHCH2(4-py)Co(dmgBF(2))(2)(OH2)](PF6)(2) (2) were prepared, in which the polypyridyl ruthenium photosensitizer and the cobaloxime catalyst are connected either by a conjugated bridge (1) or by an unconjugated one (2). Complexes 1 and 2 were used as photocatalysts for hydrogen generation. Under optimal conditions, the turnover numbers (ton) for hydrogen evolution were 38 for 1 and 48 for 2 in the presence of 300 equiv of both Et3N and [Et3NH][BF4] in the acetone solution during an 8-h irradiation of visible light (lambda > ca. 400 nm). The complex 2 with an unconjugated bridge proved to be more efficient for photochemical hydrogen generation than the complex 1 with a conjugated bridge under the same reaction condition.
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| 2. |
- Na, Yong, et al.
(författare)
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Visible light-driven electron transfer and hydrogen generation catalyzed by bioinspired 2Fe2S complexes
- 2008
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 47:7, s. 2805-2810
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Tidskriftsartikel (refereegranskat)abstract
- Complexes [{(mu-SCH2)(2)NCH2C6H5){Fe(CO)(2)L-1){Fe(CO)(2)L-2}] (L-1 = CO, L-2 = P(Pyr)(3), 2; L-1 = L-2 = P(Pyr)(3), 3) were prepared, which have the lowest reduction potentials for the mono- and double-CO-displaced diiron complexes reported so far. Hydrogen evolution, driven by visible light, was successfully observed for a three-component system, consisting of a ruthenium polypyridine complex, the biomimetic model complex 2 or 3, and ascorbic acid as both electron and proton donor in CH3CN/H2O. The electron transfer from photogenerated Ru(bPY)(3)(+) to 2 or 3 was detected by laser flash photolysis. Under optimal conditions, the total turnover number for hydrogen evolution was 4.3 based on 2 and 86 based on Ru(bPY)(3)(2+) in a three-hour photolysis.
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| 3. |
- Billsten, Helena, et al.
(författare)
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Excited-state processes in the carotenoid zeaxanthin after excess energy excitation
- 2005
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Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 109:31, s. 6852-6859
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Tidskriftsartikel (refereegranskat)abstract
- Aiming for better understanding of the large complexity of excited-state processes in carotenoids, we have studied the excitation wavelength dependence of the relaxation dynamics in the carotenoid zeaxanthin. Excitation into the lowest vibrational band of the S-2 state at 485 nm, into the 0-3 vibrational band of the S2 state at 400 nm, and into the B-2(u)+ state at 266 nm resulted in different relaxation patterns. While excitation at 485 nm produces the known four-state scheme (S-2 -> hot S-1 -> S-1 -> S-0), excess energy excitation led to additional dynamics occurring with a time constant of 2.8 ps (400 nm excitation) and 4.9 ps (266 nm excitation), respectively. This process is ascribed to a conformational relaxation of conformers generated by the excess energy excitation. The zeaxanthin S* state was observed regardless of the excitation wavelength, but its population increased after 400 and 266 nm excitation, suggesting that conformers generated by the excess energy excitation are important for directing the population toward the S* state. The S-2-S-1 internal conversion time was shortened from 135 to 70 fs when going from 485 to 400 nm excitation, as a result of competition between the S-2-S-1 internal conversion from the vibrationally hot S2 state and S2 vibrational relaxation. The S, lifetime of zeaxanthin was within experimental error the same for all excitation wavelengths, yielding similar to 9 ps. No long-lived species have been observed after excitation by femtosecond pulses regardless of the excitation wavelength, but excitation by nanosecond pulses at 266 nm generated both zeaxanthin triplet state and cation radical.
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| 4. |
- Li, Chaoyan, et al.
(författare)
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Anthraquinone dyes as photosensitizers for dye-sensitized solar cells
- 2007
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 91:19, s. 1863-1871
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Tidskriftsartikel (refereegranskat)abstract
- Three anthraquitione dyes with carboxylic acid as anchoring group are designed and synthesized as sensitizers for dye-sensitized solar cells (DSSCs). Preliminary photophysical and photoelectrochemical measurements show that these anthraquinone dyes have very low performance on DSSC applications, although they have broad and intense absorption spectra in the visible region (up to 800nm). Transient absorption kinetics, fluorescence lifetime measurements and density functional theory (DFT) calculations are conducted to investigate the cause of such low DSSC performance for these dyes. The results show that the strong electron -withdrawing character of the two carbonyl groups on anthraquinone framework may lie behind the low performance by suppressing the efficient electron injection from the dye to the conduction band of TiO2.
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| 5. |
- Li, Minna, et al.
(författare)
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Oligo thiophene-2-yl-vinyl bridged mono- and binuclear ruthenium(II) tris-bipyridine complexes : Synthesis, photophysics, electrochemistry and electrogenerated chemiluminescence
- 2008
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Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X .- 1872-8561. ; 693:1, s. 46-56
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Tidskriftsartikel (refereegranskat)abstract
- A series of mono- and binuclear ruthenium(II) tris-bipyridine complexes tethered to oligothienylenevinyleries have been synthesized and characterized by H-1 NMR, C-13 NMR and TOF-MS spectrometry. Photophysics, electrochemistry and electrogenerated chemiluminescence (ECL) properties of these complexes are investigated. The electronic absorption spectra of the mononuclear ruthenium complexes show a significant red shift both at MLCT (metal-to-ligand charge transfer) and pi-pi* transitions of oligothienylenevinylenes with increase in the number of thiophenyl-2-yl-vinyl unit. For the binuclear complexes these two absorption bands are overlapped.) All the metal complexes have very weak emission compared to that of the reference complex Ru(bpy)(3)(2+). The first reduction potentials of all mononuclear ruthenium complexes are less negative than that of Ru(bpy)(3)(2+), due to the moderate electron-withdrawing effect of oligothienylenevinylenes. For binuclear ruthenium complexes, only one Ru(II/III) oxidation peak (E-1/2=0.96V vs. Ag/Ag+) was observed, suggesting a weak interaction between two metal centers. Three successive reduction processes of bipyridine ligands are similar among all ruthenium complexes except for RuTRu, which has a very sharp peak owing to the accumulation of neutral product oil the electrode surface. All these ruthenium complexes exhibited different ECL property in CH3CN solution without any additional reductant or oxidant. For three mononuclear ruthenium complexes, the ECL intensity strengthens with increase in the number of thiophene-2-yl-vinyl unit. However, the ECL efficiency dramatically decreased in the binuclear ruthenium complexes. The ECL efficiencies of all the)2+, reported complexes do not exceed that of Ru(bpy 3 where the ECL efficiency decreases in the order of RuTRu > Ru3T > Ru2T > RuT > Ru2TRu (RuT, bis-2,2'-bipyridyl-(4-metliyl-4'-(2-thienylethenyl)-2,2'-bipyridine) ruthenium dihexafluorophosphate; Ru2T, bis-2,2'-bipyridyl-(4-methyl-4'-{(E) -2-[5-((E) -2-thienylethenyl)-thienylethenyl])-2,2'-bipyridine)ruthenium dihexafluorophosphate; Ru3T, bis-2,2'-bipyridyl-(4-methyl-4'-[(E)-2-{(E)-2-[5-((E)-2-thienylethenyl)- thienylethenyl])}-2,2'-bipyridine) ruthenium dihexafluorophosphate; RuTRu, bis-2,2'-bipyridyl-ruthenium-bis-[2-((E)-4'-methyl-2,2'-bipyridinyl-4)-e thenyl]-thienyl-bis-2,2'-bipyridyl-ruthenium tetrahexafluorophosphate; Ru2TRu, bis-2,2'-bipyridyl-ruthenium-(E)-1,2-bis-{2-[2-((E)-4'-methyl-2,2'-bipyr idinyl-4)-ethenyl]-thienyl}ethenyl-bis-2,2'-bipyridyl-ruthenium tetrahexafluorophosphate).
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| 6. |
- Li, Ping, et al.
(författare)
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FeFe -Hydrogenase active site models with relatively low reduction potentials : Diiron dithiolate complexes containing rigid bridges
- 2008
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Ingår i: Journal of Inorganic Biochemistry. - : Elsevier BV. - 0162-0134 .- 1873-3344. ; 102:4, s. 952-959
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Tidskriftsartikel (refereegranskat)abstract
- Three diiron dithiolate complexes containing rigid and conjugated bridges, [mu-SC6H4-2-(CO)S-mu]Fe-2(CO)(6) (1), [2-mu-SC5H3N-3-(CO)S-mu]Fe-2(CO)(6) (2). and the PPh3-monosubstituted complex [mu-SC6H4-2-(CO)S-mu]Fe-2(CO)(5)(PPh3) (1-P), were prepared as biomimetic models for the [FeFe]-hydrogenase active site. The structures of complexes 1 and 2 were determined by single crystal X-ray analysis, which shows that each complex features a rigid coplanar dithiolate bridge with a 2-3 degrees deviation from the bisect plane of the molecule. The influence of the rigid bridge on the reduction potentials of complexes 1, 2 and 1-P was investigated by electrochemistry. The cyclic voltammograms of complexes 1 and 2 display large positive shifts for the primary reduction potentials, that is, 380-480 mV in comparison to that of the pdt-bridged (pdt = propane-1,3-dithiolato) complex (mu-pdt)Fe-2(CO)(6) and 160-260 mV to that of the bdt-bridged (bdt = benzene- 1,2-dithiolato) analogue ([mu-bdt)Fe-2(CO)(6).
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| 7. |
- Li, Xueqiang, et al.
(författare)
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Noncovalent assembly of a metalloporphyrin and an iron hydrogenase active-site model : Photo-induced electron transfer and hydrogen generation
- 2008
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207 .- 1089-5647. ; 112:27, s. 8198-8202
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Tidskriftsartikel (refereegranskat)abstract
- A noncovalent assembly of a pyridyl-functionalized hydrogenase active-site model complex and zinc tetraphenylporphyrin has been obtained and characterized. Upon light irradiation, fluorescence quenching by electron transfer was observed from the singlet excited state of the porphyrin to the diiron center, and the mechanism was verified by fluorescence lifetime and transient absorption spectroscopic measurements. In contrast to molecular dyads linked by covalent bonds, the assembled system was designed to avoid charge recombination via complex dissociation after photo-induced electron transfer. Visible light-driven hydrogen generation was observed from this self-assembled system. The assembling strategy employed in this study has the potential to be used for any other hydrogenase models in the future.
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| 8. |
- Liu, Xien, et al.
(författare)
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Synthesis, electrochemical, and photophysical studies of multicomponent systems based on porphyrin and ruthenium(II) polypyridine complexes
- 2007
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Ingår i: Tetrahedron. - : Elsevier BV. - 0040-4020 .- 1464-5416. ; 63:37, s. 9195-9205
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Tidskriftsartikel (refereegranskat)abstract
- Two ruthenium tris-bipyridine functionalized porphyrins 4, 8 and their Zn derivatives 4-Zn, 8-Zn were designed, synthesized, and characterized. The redox potentials of these complexes as well as their corresponding monomeric reference porphyrin and ruthenium bipyridine complexes were also measured for comparison. Primary dynamic studies on the electron injection and backing recombination between these complexes and TiO2 nanoparticles were carried out by means of transient absorption spectroscopy. The results indicate that a long-lived charge separation state was obtained in these assemblies.
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| 9. |
- Na, Yong, et al.
(författare)
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Intermolecular electron transfer from photogenerated Ru(bpy)(3)(+) to 2Fe2S model complexes of the iron-only hydrogenase active site
- 2007
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 46:10, s. 3813-3815
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Tidskriftsartikel (refereegranskat)abstract
- Visible light-driven intermolecular electron transfer was observed from a reduced species Ru(bpy)(3)(+), photogenerated via a reductive quenching of the ruthenium photosensitizer by a diethyldithiocarbamate anion, to bioinspired [2Fe2S] model complexes of the iron-only hydrogenase active site. The results indicate that Ru(bpy)(3)(2+) can act as a photoactive functional model of the [4Fe4S] cluster, playing the role of an electron-transfer relay. The photogenerated (FeFe0)-Fe-I species, which is proposed to be a crucial intermediate for proton reduction catalyzed electrochemically by the [2Fe2S] complexes, gives promise in the light-driven dihydrogen evolution using diiron complexes as surrogates of noble platinum catalysts.
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| 10. |
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| 11. |
- Pan, Jingxi, et al.
(författare)
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Stepwise charge separation from a ruthenium-tyrosine complex to a nanocrystalline TiO2 film
- 2004
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 108:34, s. 12904-12910
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Tidskriftsartikel (refereegranskat)abstract
- A supramolecular complex composed of Ru(II) tris-bipyridine, tyrosine, and dipicolylamine was synthesized and characterized. This complex was attached to TiO2 nanocrystalline films via ester groups at the Ru(II) chromophore, and photoinduced multistep electron transfer was investigated by laser flash photolysis and electron paramagnetic resonance techniques. Following ultrafast electron injection from the metal-ligand charge transfer excited states of Ru(II) to the conduction band of TiO2, fast intramolecular electron transfer from the tyrosine moiety to the photogenerated Ru(III) was observed, characterized by a rate constant of similar to2 x 10(6) s(-1). By comparison of recovery kinetics at the isosbestic point with that of the reference compound lacking the tyrosine, it was found that the intramolecular electron-transfer efficiency is 90%. A hydrogen-bond-promoted electron-transfer mechanism is proposed.
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| 12. |
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| 13. |
- Sun, Shiguo, et al.
(författare)
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Host-guest chemistry and light driven molecular lock of Ru(bpy)(3)-viologen with cucurbit 7-8 urils
- 2007
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 111:47, s. 13357-13363
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Tidskriftsartikel (refereegranskat)abstract
- Host-guest chemistry and photoinduced electron-transfer processes have been studied in the systems containing Ru(bPy)(3) complex covalently linked to viologen as a guest molecule and cucurbit[n]urils (n = 7, 8) as host molecules in aqueous solution. The Ru(bpy)(3)-viologen complex,[Ru(2,2 '-bipyridine)(2)(4-(4-(1 '-methyl-4,4 '-bipyridinediium-1-yl)butyl)-4 '-methyl-2,2 '-bipyridine)]Cl-4(denoted as RU2+-MV2+, 1) was shown to form stable 1:1 inclusion complexes with cucurbit[7]uril (CB[7]) and cucurbit[8] uril (CB[8]). The binding modes are slightly different with CB[7] and CB[8]. CB[7] preferentially binds to part of the viologen residue in 1 together with the butyl chain, whereas CB[8] preferentially encloses the whole viologen residue. Photoinduced intramolecular electron transfer from the excited-state of the Ru moiety to MV2+ which is inserted into the cavity of the CBs occurred. Long-lived charge-separated states RU3+-MV+center dot, were generated with the lifetimes of 280 ns with CB[7] and 2060 ns with CB[8]. This shows that CBs can slow down the charge recombination within supramolecular systems, and the difference in lifetimes seems to be due to the difference in binding modes. In the presence of a sacrificial electron donor triethanolarnine, light-driven formation of a dimer of MV+center dot inside the CB[8] cavity was observed. This locked molecular dimer can be unlocked by molecular oxygen to give back the original form of the molecular dyad 1 with the MV2+ moiety inserted in the cavity of CB[8]. The processes could be repeated several times and showed nice reversibility.
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| 14. |
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| 15. |
- Tian, Haining, et al.
(författare)
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A triphenylamine dye model for the study of intramolecular energy transfer and charge transfer in dye-sensitized solar cells.
- 2008
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 18:21, s. 3461-3468
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Tidskriftsartikel (refereegranskat)abstract
- A novel dye (2TPA-R), contg. two triphenylamine (TPA) units connected by a vinyl group and rhodanine-3-acetic acid as the electron acceptor, is designed and synthesized successfully to reveal the working principles of org. dye in dye-sensitized solar cells (DSSCs). 2TPA and TPA-R, which consist of two TPA units connected by vinyl and a TPA unit linked with rhodanine-3-acetic acid, resp., are also synthesized as refs. to study the intramol. energy transfer (EnT) and charge transfer (ICT) processes of 2TPA-R in CH2Cl2 soln. and on a TiO2 surface. The results suggest that the intramol. EnT and ICT processes show a pos. effect on the performance of DSSCs. However, the flexible structure and less-adsorbed amt. of dye on TiO2 may make it difficult to improve the efficiency of DSSCs. This study on intramol. EnT and ICT processes acts as a guide for the design and synthesis of efficient org. dyes in the future. [on SciFinder(R)]
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| 16. |
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| 17. |
- Wolpher, Henriette, et al.
(författare)
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Synthesis and electron transfer studies of ruthenium-terpyridine-based dyads attached to nanostructured TiO2
- 2007
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 46:3, s. 638-651
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Tidskriftsartikel (refereegranskat)abstract
- A series of bis(terpyridine)Ru-II complexes have been prepared, where one of the terpyridines is functionalized in the 4'-position by a phosphonic or carboxylic acid group for attachment to TiO2. The other is functionalized, also in the 4'-position, by a potential electron donor. In complexes 1a, 3a, and 4a,b, this donor is tyrosine or hydrogen-bonded tyrosine, while in 2a it is carotenoic amide. The synthesis and photophysical properties of the complexes are discussed. On irradiation with visible light, the formation of a long-lived charge-separated state was anticipated, via primary electron ejection into the TiO2, followed by secondary electron transfer from the donor to the photogenerated Ru-III. However, such a charge-separated state could be observed with certainty only with complex 2a. To explain the result, quantum chemical calculations were performed on the different types of complexes.
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| 18. |
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| 19. |
- Xu, Y. H., et al.
(författare)
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Synthesis and characterization of dinuclear ruthenium complexes covalently linked to Ru-II tris-bipyridine : An approach to mimics of the donor side of photosystem II
- 2005
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 11:24, s. 7305-7314
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Tidskriftsartikel (refereegranskat)abstract
- To mimic the electron-donor side of photosystem II (PSII), three trinuclear ruthenium complexes (2, 2a, 2b) were synthesized. In these compl plexes, a mixed-valent dinuclear Ru-2(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 Ru-2(II,III) moieties in the complexes readily undergo reversible one-electron reduction and one-electron oxidation to give the Ru-2(II,II) and Ru-2(II,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 Ru-2(II,III) moiety to photogenerated Ru-III was observed. The resulting long-lived Ru-2(III,III) state decays on the millisecond timescale.
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| 20. |
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