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  • 1.
    Andersson, Claes-Henrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Berggren, Gustav
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Synthesis and IR Spectroelectrochemical Studies of a [60]Fulleropyrrolidine-(tricarbonyl)chromium Complex: Probing C-60 Redox States by IR Spectroscopy2011In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 11, p. 1744-1749Article in journal (Refereed)
    Abstract [en]

    The synthesis of a new fulleropyrrolidine-(tricarbonyl)chromium complex: 1-methyl-2-(4-methoxyphenyl)-3,4-[60]fulleropyrrolidine-(tricarbonyl)chromium is described together with its characterization by IR, NMR and cyclic voltammetry. IR spectro-electrochemistry has been used to probe the redox level of the fullerene derivative via the relative position of the vibrational bands of the CO ligands, which are sensitive to the electronic state of the complex. Other strategies to incorporate a tricarbonylchromium moiety to fullerene C60 are also briefly discussed and evaluated.

  • 2.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Reductive Diphosphene Formation From W(CO)5-Coordinated Dichlorophosphanes2011In: Phosphorus Sulfur and Silicon and the Related Elements, ISSN 1042-6507, E-ISSN 1563-5325, Vol. 186, no 4, p. 664-665Article in journal (Refereed)
    Abstract [en]

    A bis-[W(CO)(5)]-coordinated (Bu-t)(2)diphosphene was prepared from the corresponding [W(CO)(5)]-(BuPCl2)-Bu-t by treatment with LiAlH4.

  • 3.
    Baebprasert, Wipawee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Jantaro, Saowarath
    Khetkorn, Wanthanee
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Incharoensakdi, Aran
    Increased H(2) production in the cyanobacterium Synechocystis sp strain PCC 6803 by redirecting the electron supply via genetic engineering of the nitrate assimilation pathway2011In: Metabolic engineering, ISSN 1096-7176, E-ISSN 1096-7184, Vol. 13, no 5, p. 610-616Article in journal (Refereed)
    Abstract [en]

    The unicellular cyanobacterium Synechocystis sp. strain PCC 6803 contains a single bidirectional NiFe-Hox-hydrogenase, which evolves hydrogen under certain environmental conditions. The nitrate assimilation pathway is a potential competing pathway that may reduce the electron flow to the hydrogenase and thereby limit hydrogen production. To improve H(2) production, the nitrate assimilation pathway was disrupted by genetic engineering to redirect the electron flow towards the Hox-hydrogenase. Mutant strains disrupted in either nitrate reductase (Delta narB) or nitrite reductase (Delta nirA) or both nitrate reductase and nitrite reductase (Delta narB:Delta nirA) were constructed and tested for their ability to produce hydrogen. H(2) production and Hox-hydrogenase activities in all the mutant strains were higher than those in wild-type. Highest H(2) production was observed in the Delta narB:Delta nirA strain. Small changes were observed for Hox-hydrogenase enzyme activities and only minor changes in transcript levels of hoxH and hoxY were not correlated with H(2) production. The results suggest that the high rate of H(2) production observed in the Delta narB:Delta nirA strain of the cyanobacterium Synechocystis sp. strain PCC 6803 is the result of redirecting the electron supply from the nitrate assimilation pathway, through genetic engineering, towards the Hox-hydrogenase.

  • 4.
    Baebprasert, Wipawee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Karnchanatat, Aphichart
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Incharoensakdi, Aran
    Na(+)-stimulated nitrate uptake with increased activity under osmotic upshift in Synechocystis sp strain PCC 68032011In: World Journal of Microbiology & Biotechnology, ISSN 0959-3993, E-ISSN 1573-0972, Vol. 27, no 10, p. 2467-2473Article in journal (Refereed)
    Abstract [en]

    In the non-diazotrophic cyanobacterium Synechocystis sp. strain PCC 6803, an osmolality of 30 and 40 mosmol/kg sorbitol and NaCl resulted in 3.5- and 4.5-fold increase of nitrate uptake, respectively. The NaCl-stimulated uptake was abolished by treatment with chloramphenicol. At 25 mosmol/kg or higher, NaCl induced higher nitrate uptake than sorbitol suggesting an ionic effect of Na(+). The nitrate uptake in Synechocystis showed K (s) and V (max) values of 46 mu M and 1.37 mu mol/min/mg Chl, respectively. Mutants disrupted in nitrate and nitrite reductase exhibited a decreased nitrate uptake. Ammonium, chlorate, and dl-glyceraldehyde caused a reduction of nitrate uptake. Dark treatment caused a drastic reduction of uptake by 70% suggesting an energy-dependent system. Nitrate transport was sensitive to various metabolic inhibitors including those dissipating proton gradients and membrane potential. The results suggest that nitrate uptake in Synechocystis is stimulated by Na(+) ions and requires energy provided by the functioning electron transport chain.

  • 5. Ballout, Fouad
    et al.
    Krassen, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Kopf, Ilona
    Ataka, Kenichi
    Bruendermann, Erik
    Heberle, Joachim
    Havenith, Martina
    Scanning near-field IR microscopy of proteins in lipid bilayers2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 48, p. 21432-21436Article in journal (Refereed)
    Abstract [en]

    We use infrared near-field microscopy to chemically map the morphology of biological matrices. The investigated sample is built up from surface-tethered membrane proteins (cytochrome c oxidase) reconstituted in a lipid bilayer. We have carried out infrared near-field measurements in the frequency range between 1600 and 1800 cm(-1). By simultaneously recording the topography and chemical fingerprint of the protein-tethered lipid bilayer with a lateral resolution of 80 nm x 80 nm, we were able to probe locally the chemical signature of this membrane and to provide a local map of its surface morphology.

  • 6.
    Berggren, Gustav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Thapper, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Huang, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Eriksson, Lars
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Anderlund, Magnus F.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Mechanistic Studies on the Water-Oxidizing Reaction of Homogeneous Manganese-Based Catalysts: Isolation and Characterization of a Suggested Catalytic Intermediate2011In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 50, no 8, p. 3425-3430Article in journal (Refereed)
    Abstract [en]

    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 complexesconsisting of Mn2 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.

  • 7.
    Beyler, Maryline
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Ezzaher, Salah
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Karnahl, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Santoni, Marie-Pierre
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Pentacoordinate iron complexes as functional models of the distal iron in [FeFe] hydrogenases2011In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 47, no 42, p. 11662-11664Article in journal (Refereed)
    Abstract [en]

    Mononuclear pentacoordinate iron complexes with a free coordination site were prepared as mimics of the distal Fe (Fe(d)) in the active site of [FeFe] hydrogenases. The complexes catalyze the electrochemical reduction of protons at mild overpotential.

  • 8.
    Camsund, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Devine, Ellenor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Holmqvist, Marie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Yohanoun, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Stensjö, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    A HupS-GFP fusion protein demonstrates a heterocyst-specific localization of the uptake hydrogenase in Nostoc punctiforme2011In: FEMS Microbiology Letters, ISSN 0378-1097, E-ISSN 1574-6968, Vol. 316, no 2, p. 152-159Article in journal (Refereed)
    Abstract [en]

    All diazotrophic filamentous cyanobacteria contain an uptake hydrogenase that is involved in the reoxidation of H-2 produced during N-2-fixation. In Nostoc punctiforme ATCC 29133, N-2-fixation takes place in the microaerobic heterocysts, catalysed by a nitrogenase. Although the function of the uptake hydrogenase may be closely connected to that of nitrogenase, the localization in cyanobacteria has been under debate. Moreover, the subcellular localization is not understood. To investigate the cellular and subcellular localization of the uptake hydrogenase in N. punctiforme, a reporter construct consisting of the green fluorescent protein (GFP) translationally fused to HupS, within the complete hupSL operon, was constructed and transferred into N. punctiforme on a self-replicative vector by electroporation. Expression of the complete HupS-GFP fusion protein was confirmed by Western blotting using GFP antibodies. The N. punctiforme culture expressing HupS-GFP was examined using laser scanning confocal microscopy, and fluorescence was exclusively detected in the heterocysts. Furthermore, the fluorescence in mature heterocysts was localized to several small or fewer large clusters, which indicates a specificity of the subcellular localization of the uptake hydrogenase.

  • 9.
    Chen, Guiying
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Allahverdiyeva, Yagut
    Aro, Eva-Mari
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Electron paramagnetic resonance study of the electron transfer reactions in photosystem II membrane preparations from Arabidopsis thaliana2011In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1807, no 2, p. 205-215Article in journal (Refereed)
    Abstract [en]

    Arabidopsis thaliana is widely used as a model organism in plant biology as its genome has been sequenced and transformation is known to be efficient. A large number of mutant lines and genomic resources are available for Arabidopsis. All this makes Arabidopsis a useful tool for studies of photosynthetic reactions in higher plants. In this study, photosystem II (PSII) enriched membranes were successfully isolated from thylakoids of Arabidopsis plants and for the first time the electron transfer cofactors in PSII were systematically studied using electron paramagnetic resonance (EPR) spectroscopy. EPR signals from both of the donor and acceptor sides of PSII, as well as from auxiliary electron donors were recorded. From the acceptor side of PSII, EPR signals from Q(A)(-)Fe(2+) and Phe(-)Q(A)(-)Fe(2+) as well as from the free Phe(-) radical were observed. The multiline EPR signals from the S-0- and S-2-states of CaMn4Ox-cluster in the water oxidation complex were characterized. Moreover, split EPR signals, the interaction signals from Y-Z center dot and CaMn4Ox-cluster in the S-0-, S-1-, S-2-, and the S-3-state were induced by illumination of the PSII membranes at 5 K and characterized. In addition, EPR signals from auxiliary donors Y-D center dot, Chl(+) and cytochrome b(559) were observed. In total, we were able to detect about 20 different EPR signals covering all electron transfer components in PSII. Use of this spectroscopic platform opens a possibility to study PSII reactions in the library of mutants available in Arabidopsis.

  • 10. Erdem, Oezlen F.
    et al.
    Schwartz, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Stein, Matthias
    Silakov, Alexey
    Kaur-Ghumaan, Sandeep
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Huang, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Reijerse, Edward J.
    Lubitz, Wolfgang
    A Model of the [FeFe] Hydrogenase Active Site with a Biologically Relevant Azadithiolate Bridge: A Spectroscopic and Theoretical Investigation2011In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 50, no 6, p. 1439-1443Article in journal (Refereed)
    Abstract [en]

    Convincing evidence for the presence of a nitrogen atom in the dithiolate bridge of the active site of native [FeFe] hydrogenases (B) is provided by a spectroscopic, electrochemical, and theoretical study of a well-characterized structural mimic of the [FeFe] hydrogenase subcluster (picture: 14N matched-HYSCORE spectrum of the model compound A). This result should help to understand the mechanism of dihydrogen conversion and production.

  • 11. Garcia-Bosch, Isaac
    et al.
    Company, Anna
    Cady, Clyde W.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Browne, Wesley R.
    Ribas, Xavi
    Costas, Miquel
    Evidence for a Precursor Complex in C-H Hydrogen Atom Transfer Reactions Mediated by a Manganese(IV) Oxo Complex2011In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 50, no 25, p. 5648-5653Article in journal (Refereed)
  • 12. Garcia-Cerdan, Jose G.
    et al.
    Kovacs, Laszlo
    Toth, Tuende
    Kereiche, Sami
    Aseeva, Elena
    Boekema, Egbert J.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Funk, Christiane
    Schröder, Wolfgang P.
    The PsbW protein stabilizes the supramolecular organization of photosystem II in higher plants2011In: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313X, Vol. 65, no 3, p. 368-381Article in journal (Refereed)
    Abstract [en]

    PsbW, a 6.1-kDa low-molecular-weight protein, is exclusive to photosynthetic eukaryotes, and associates with the photosystem II (PSII) protein complex. In vivo and in vitro comparison of Arabidopsis thaliana wild-type plants with T-DNA insertion knock-out mutants completely lacking the PsbW protein, or with antisense inhibition plants exhibiting decreased levels of PsbW, demonstrated that the loss of PsbW destabilizes the supramolecular organization of PSII. No PSII-LHCII supercomplexes could be detected or isolated in the absence of the PsbW protein. These changes in macro-organization were accompanied by a minor decrease in the chlorophyll fluorescence parameter F-V/F-M, a strongly decreased PSII core protein phosphorylation and a modification of the redox state of the plastoquinone (PQ) pool in dark-adapted leaves. In addition, the absence of PsbW protein led to faster redox changes in the PQ pool, i.e. transitions from state 1 to state 2, as measured by changes in stationary fluorescence (F-S) kinetics, compared with the wild type. Despite these dramatic effects on macromolecular structure, the transgenic plants exhibited no significant phenotype under normal growth conditions. We suggest that the PsbW protein is located close to the minor antenna of the PSII complex, and is important for the contact and stability between several PSII-LHCII supercomplexes.

  • 13.
    Geng, Xue-Li
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Acetylene-Expanded Dendralene Segments with Exotopic Phosphaalkene Units2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 43, p. 12153-12162Article in journal (Refereed)
    Abstract [en]

    Bis-TMS protected C, C-diacetylenic phosphaalkene (A(2)PA) 1 (Mes*P=C(C CTMS)(2); Mes*=2,4,6-tBu(3)Ph) has been used as a building block for the construction of butadiyne-expanded dendralene fragments in which phosphaalkenes feature as exotopic double bonds. Treatment of 1 with CuCl gives rise to a Cu(I) acetylide that is selectively formed at the acetylene trans to the Mes* group. The cis-TMS-acetylene engages in similar chemistry, albeit at higher temperatures and longer reaction times. The differentiation between the two acetylene termini of 1 allows for the controlled synthesis of the title compounds by a variety of different Cu- and Pd-catalyzed oxidative acetylene homo- and heterocoupling protocols. Crystallographic characterization of A(2)PA 1 and dimeric Mes*P=C(C CR(1))C(4)(R(2)C C)C=PMes* (3b, R(1)=R(2)=Ph; 6, R(1)=R(2)=TMS), and 10 (R(1)=R(2)=C CPh) verifies that the stereochemistry across the P=C bond is conserved during the coupling reactions, whereas spectroscopic evidence reveals cis/trans isomerization in an iodo-substituted A(2)PA intermediate 4 (Mes*P=C(C CTMS)(C CI). UV/Vis spectroscopic and electrochemical studies reveal that efficient pi conjugation operates through the entire acetylenic phosphaalkene framework, even in the cross-conjugated dimeric structures. The P centers contribute considerably to the frontier molecular orbitals of the compounds, thereby leading to smaller HOMO-LUMO gaps than in all-carbon-based congeners. Phenyl- and/or ethynylphenyl substituents at the A(2)PA framework influence the HOMO and LUMO to a varying degree depending on their relationship to the Mes* group, thus enabling a fine-tuning of the frontier molecular orbitals of the compounds.

  • 14. Grasse, Nicole
    et al.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Becker, Kristin
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Roegner, Matthias
    Nowaczyk, Marc M.
    Role of Novel Dimeric Photosystem II (PSII)-Psb27 Protein Complex in PSII Repair2011In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 286, no 34, p. 29548-29555Article in journal (Refereed)
    Abstract [en]

    The multisubunit membrane protein complex Photosystem II (PSII) catalyzes one of the key reactions in photosynthesis: the light-driven oxidation of water. Here, we focus on the role of the Psb27 assembly factor, which is involved in biogenesis and repair after light-induced damage of the complex. Weshow that Psb27 is essential for the survival of cyanobacterial cells grown under stress conditions. The combination of cold stress (30 degrees C) and high light stress (1000 mu mol of photons x m(-2) x s(-1)) led to complete inhibition of growth in a Delta psb27 mutant strain of the thermophilic cyanobacterium Thermosynechococcus elongatus, whereas wild-type cells continued to grow. Moreover, Psb27-containing PSII complexes became the predominant PSII species in preparations from wild-type cells grown under cold stress. Two different PSII-Psb27 complexes were isolated and characterized in this study. The first complex represents the known monomeric PSII-Psb27 species, which is involved in the assembly of PSII. Additionally, a novel dimeric PSII-Psb27 complex could be allocated in the repair cycle, i.e. in processes after inactivation of PSII, by (15)N pulse-label experiments followed by mass spectrometry analysis. Comparison with the corresponding PSII species from Delta psb27 mutant cells showed that Psb27 prevented the release of manganese from the previously inactivated complex. These results indicate a more complex role of the Psb27 protein within the life cycle of PSII, especially under stress conditions.

  • 15.
    Hammarström, Leif
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Proton-coupled electron transfer of tyrosines in Photosystem II and model systems for artificial photosynthesis: the role of a redox-active link between catalyst and photosensitizer2011In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 4, no 7, p. 2379-2388Article in journal (Refereed)
    Abstract [en]

    Water oxidation in Photosystem II is dependent on a particular amino acid residue, Tyrosine(Z). This is a redox intermediate in steady state oxygen evolution and transfers electrons from the water splitting CaMn4 cluster to the central chlorophyll radical P-680(+). This Perspective discusses the functional principles of Tyrosine(Z) as a proton-coupled redox active link, as well as mechanistic studies of synthetic model systems and implications for artificial photosynthesis. Experimental studies of temperature dependence and kinetic isotope effects are important tools to understand these reactions. We emphasize the importance of proton transfer distance and hydrogen bond dynamics that are responsible for variation in the rate of PCET by several orders of magnitude. The mechanistic principles discussed and their functional significance are not limited to tyrosine and biological systems, but are important to take into account when constructing artificial photosynthetic systems. Of particular importance is the role of proton transfer management in water splitting and solar fuel catalysis.

  • 16.
    Hammarström, Leif
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Winkler, Jay R.
    Gray, Harry B.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Shedding Light on Solar Fuel Efficiencies2011In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 333, no 6040, p. 288-288Article in journal (Refereed)
  • 17.
    Havelius, Kajsa G. V.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Su, Ji-Hu
    Han, Guangye
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Ho, Felix M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    The formation of the split EPR signal from the S-3 state of Photosystem II does not involve primary charge separation2011In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1807, no 1, p. 11-21Article in journal (Refereed)
    Abstract [en]

    Metalloradical EPR signals have been found in intact Photosystem II at cryogenic temperatures. They reflect the light-driven formation of the tyrosine Z radical (Y-z(center dot)) in magnetic interaction with the CaMn4 cluster in a particular S state. These so-called split EPR signals, induced at cryogenic temperatures, provide means to study the otherwise transient Y-z(center dot) and to probe the S states with EPR spectroscopy. In the S-0 and S-1 states, the respective split signals are induced by illumination of the sample in the visible light range only. In the S-3 state the split EPR signal is induced irrespective of illumination wavelength within the entire 415-900 nm range (visible and near-IR region) [Su, J. H., Havelius, K. G. V., Ho, F. M., Han, G., Mamedov, F., and Styring, S. (2007) Biochemistry 46. 10703-10712]. An important question is whether a single mechanism can explain the induction of the Split S-3 signal across the entire wavelength range or whether wavelength-dependent mechanisms are required. In this paper we confirm that the Y-z(center dot) radical formation in the S-1 state, reflected in the Split S-1 signal, is driven by P680-centered charge separation. The situation in the S-3 state is different. In Photosystem II centers with pre-reduced quinone A (Q(A)), where the P680-centered charge separation is blocked, the Split S-3 EPR signal could still be induced in the majority of the Photosystem II centers using both visible and NIR (830 nm) light. This shows that P680-centered charge separation is not involved. The amount of oxidized electron donors and reduced electron acceptors (Q(A)(-)) was well correlated after visible light illumination at cryogenic temperatures in the S-1 state. This was not the case in the S-3 state, where the Split S-3 EPR signal was formed in the majority of the centers in a pathway other than P680-centered charge separation. Instead, we propose that one mechanism exists over the entire wavelength interval to drive the formation of the Split S-3 signal. The origin for this, probably involving excitation of one of the Mn ions in the CaMn4 cluster in Photosystem II, is discussed.

  • 18.
    Karnahl, Michael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Kuhnt, Christian
    Ma, Fei
    Yartsev, Arkady
    Schmitt, Michael
    Dietzek, Benjamin
    Rau, Sven
    Popp, Juergen
    Tuning of Photocatalytic Hydrogen Production and Photoinduced Intramolecular Electron Transfer Rates by Regioselective Bridging Ligand Substitution2011In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 12, no 11, p. 2101-2109Article in journal (Refereed)
    Abstract [en]

    Artificial photosynthesis based on supramolecular photocatalysts offers the unique possibility to study the molecular processes underlying catalytic conversion of photons into chemical fuels in great detail and to tune the properties of the photocatalyst by alterations of the molecular framework. Herein we focus on both possibilities in studying the photocatalytic reduction of protons by derivatives of the well-known photocatalyst [(tbbpy)(2)Ru(tpphz)PdCl(2)](PF(6))(2) [4,4'-di-tert-butyl-2,2'-bipyridine (tbbpy), tetrapyrido[3,2-a:2',3'-c:3 '',2 ''-h:2'", 3'"-j]phenazine (tpphz)]. We report on a modified photocatalyst where the crucial bridging ligand tpphz is substituted by bromine and investigate the effect of the structural variation on the catalytic properties of the complex and its ultrafast intramolecular charge transfer behavior. It is found that structural modification stabilizes the phenanthroline-centered metal-to-ligand charge-transfer state on the tpphz moiety, thereby reducing the electron transfer gradient across the entire electron-relaying bridging ligand and at the same time accelerating nanosecond ground-state recovery. The same structural modifications cause an overall reduction of the catalytic activity of the complex. Thus, the results highlight the potential of small structural variations in the molecular framework of supramolecular catalysts in understanding the photoinduced charge-transfer processes and optimizing their catalytic performance.

  • 19.
    Krassen, Henning
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Heberle, Joachim
    In vitro hydrogen production-using energy from the sun2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 1, p. 47-57Article in journal (Refereed)
    Abstract [en]

    Using solar energy to produce molecular hydrogen is a promising way to supply the civilization with clean energy. Nature provides the key components to collect solar energy as well as to reduce protons, scientists have developed mimics of these enzymatic centers and also found new ways to catalyze the same reactions. This perspective article surveys the different components and in particular the various coupling possibilities of a light sensitizer and catalyst. Pros and cons are discussed.

  • 20.
    Krassen, Henning
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Stripp, Sven T.
    Boehm, Nadine
    Berkessel, Albrecht
    Happe, Thomas
    Ataka, Kenichi
    Heberle, Joachim
    Tailor-Made Modification of a Gold Surface for the Chemical Binding of a High-Activity [FeFe] Hydrogenase2011In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 7, p. 1138-1146Article in journal (Refereed)
    Abstract [en]

    Hydrogenases are iron-sulfur proteins that catalyze hydrogen turnover in a wide range of microorganisms. Three different classes have been described, and among these [FeFe] hydrogenases are the most active in H-2 evolution. Hydrogenases are redox enzymes that have been shown to exchange electrons with graphite and modified noble metal electrodes. Making use of the latter, diffusible electron carriers are required to enable redox catalysis, as proteins do not specifically bind to the electrode surface. Diffusion-limited electron transfer can be replaced by electron injection into immobilized hydrogenase by binding the redox mediator to the electrode surface. Here, we present the synthesis and spectroelectrochemical characterization of 1-( 10-mercaptodecyl)-1'-benzyl-4,4'-bipyridinium dibromide (MBBP), which is used as redox-active linker. CrHydA1, the high-activity [FeFe] hydrogenase from Chlamydomonas reinhardtii, is immobilized on the linker-modified gold electrode. Each surface modification step is controlled in situ by surface-enhanced infrared absorption spectroscopy (SEIRAS). Functionality of the electrode-protein hybrid is demonstrated by recording the linker-supported current. The specific catalytic rate of hydrogen evolution by CrHydA1 (2.9 mu molH(2)min(-1)mg(-1) hydrogenase) promises a valuable approach for further optimization of this novel bioelectrical interface.

  • 21. Kuhnt, Christian
    et al.
    Karnahl, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Rau, Sven
    Schmitt, Michael
    Dietzek, Benjamin
    Popp, Juergen
    The impact of bromine substitution on the photophysical properties of a homodinuclear Ru-tpphz-Ru complex2011In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 516, no 1-3, p. 45-50Article in journal (Refereed)
    Abstract [en]

    Ruthenium-polypyridine complexes play an important role as photosensitizers in supramolecular photocatalysis. Using multiple Ru-centers within a single supramolecular catalyst might be a promising path for improving its efficiency. The connection of several chromophores may, however, lead to direct interaction amongst individual photoactive centers, which is at the core of the work at hand. The work focuses on the photophysics of [(tbbpy)(2)Ru(3,16-Br(2)-tpphz)Ru(tbbpy)(2)](PF(6))(4) (1, tpphz = tetrapyrido[3,2-a: 2',3'-c: 3 '',2 ''-h:2''',3'''-j] phenazine, tbbpy = 4,4'-di-tert.-butyl-2,2'-bipyridine) and aims at detailing the impact of the bromine substituents on bridging ligand photoinduced intramolecular charge-transfer dynamics. It is shown that the introduction of the bromine reduces the driving force for intra-ligand charge-transfer steps and impacts exciton-exciton annihilation at high pump intensities.

  • 22. Kumar, Kanhaiya
    et al.
    Dasgupta, Chitralekha Nag
    Nayak, Bikram
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Das, Debabrata
    Development of suitable photobioreactors for CO2 sequestration addressing global warming using green algae and cyanobacteria2011In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 102, no 8, p. 4945-4953Article, review/survey (Refereed)
    Abstract [en]

    CO2 sequestration by cyanobacteria and green algae are receiving increased attention in alleviating the impact of increasing CO2 in the atmosphere. They, in addition to CO2 capture, can produce renewable energy carriers such as carbon free energy hydrogen, bioethanol, biodiesel and other valuable biomolecules. Biological fixation of CO2 are greatly affected by the characteristics of the microbial strains, their tolerance to temperature and the CO2 present in the flue gas including SOx, NOR. However, there are additional factors like the availability of light, pH, O-2, removal, suitable design of the photobioreactor, culture density and the proper agitation of the reactor that will affect significantly the CO2 sequestration process. Present paper deals with the photobioreactors of different geometry available for biomass production. It also focuses on the hybrid types of reactors (integrating two reactors) which can be used for overcoming the bottlenecks of a single photobioreactor.

  • 23.
    Kurz, Philipp
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Wiechen, Mathias
    Biomimetic oxides for Water oxidation2012In: Nachrichten aus der Chemie, ISSN 1439-9598, E-ISSN 1868-0054, Vol. 60, no 1, p. 24-28Article in journal (Refereed)
  • 24.
    Lopes Pinto, Fernando
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Erasmie, Sven
    Blikstad, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Biochemistry.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Oliveira, Paulo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    FtsZ degradation in the cyanobacterium Anabaena sp. strain PCC 71202011In: Journal of plant physiology (Print), ISSN 0176-1617, E-ISSN 1618-1328, Vol. 168, no 16, p. 1934-1942Article in journal (Refereed)
    Abstract [en]

    In prokaryotes, cell division is normally achieved by binary fission, and the key player FtsZ is considered essential for the complete process. In cyanobacteria, much remains unknown about several aspects of cell division, including the identity and mechanism of the various components involved in the division process. Here, we report results obtained from a search of the players implicated in cell division, directly associating to FtsZ in the filamentous, heterocyst-forming cyanobacterium Anabaena sp. PCC 7120. Histidine tag pull-downs were used to address this question. However, the main observation was that FtsZ is a target of proteolysis. Experiments using various cell-free extracts, an unrelated protein, and protein blot analyses further supported the idea that FtsZ is proteolytically cleaved in a specific manner. In addition, we show evidence that both FtsZ termini seem to be equally prone to proteolysis. Taken together, our data suggest the presence of an unknown player in cyanobacterial cell division, opening up the possibility to investigate novel mechanisms to control cell division in Anabaena PCC 7120.

  • 25.
    Magnuson, Ann
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Krassen, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Stensjö, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Ho, Felix M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Modeling Photosystem I with the alternative reaction center protein PsaB2 in the nitrogen fixing cyanobacterium Nostoc punctiforme2011In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1807, no 9, p. 1152-1161Article in journal (Refereed)
    Abstract [en]

    Five nitrogen fixing cyanobacterial strains have been found to contain PsaB2, an additional and divergent gene copy for the Photosystem I reaction center protein PsaB. In all five species the divergent gene, psaB2, is located separately from the normal psaAB operon in the genome. The protein, PsaB2, was recently identified in heterocysts of Nostoc punctiforme sp. strain PCC 73102. 12 conserved amino acid replacements and one insertion, were identified by a multiple sequence alignment of several PsaB2 and PsaB1 sequences. Several, including an inserted glutamine, are located close to the iron-sulfur cluster F(x) in the electron transfer chain. By homology modeling, using the Photosystem I crystal structure as template, we have found that the amino acid composition in PsaB2 will introduce changes in critical parts of the Photosystem I protein structure. The changes are close to F(x) and the phylloquinone (PhQ) in the B-branch, indicating that the electron transfer properties most likely will be affected. We suggest that the divergent PsaB2 protein produces an alternative Photosystem I reaction center with different structural and electron transfer properties. Some interesting physiologcial consequences that this can have for the function of Photosystem I in heterocysts, are discussed.

  • 26.
    Oliveira, Paulo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Novel Insights into the Regulation of LexA in the Cyanobacterium Synechocystis sp Strain PCC 68032011In: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 193, no 15, p. 3804-3814Article in journal (Refereed)
    Abstract [en]

    The transcription factor LexA in the cyanobacterium Synechocystis sp. strain PCC 6803 has been shown to regulate genes that are not directly involved in DNA repair but instead in several different metabolic pathways. However, the signal transduction pathways remain largely uncharacterized. The present work gives novel insights into the regulation of LexA in this unicellular cyanobacterium. A combination of Northern and Western blotting, using specific antibodies against the cyanobacterial LexA, was employed to show that this transcription regulator is under posttranscriptional control, in addition to the classical and already-described transcriptional regulation. Moreover, detailed two-dimensional (2D) electrophoresis analyses of the protein revealed that LexA undergoes posttranslational modifications. Finally, a fully segregated LexA:: GFP (green fluorescent protein) fusion-modified strain was produced to image LexA's spatial distribution in live cells. The fusion protein retains DNA binding capabilities, and the GFP fluorescence indicates that LexA is localized in the innermost region of the cytoplasm, decorating the DNA in an evenly distributed pattern. The implications of these findings for the overall role of LexA in Synechocystis sp. strain PCC 6803 are further discussed.

  • 27.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Ironing Out Hydrogen Storage2011In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 333, no 6050, p. 1714-1715Article in journal (Other academic)
  • 28. Planas, Nora
    et al.
    Vigara, Laura
    Cady, Clyde
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Miro, Pere
    Huang, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Styring, Stenbjorn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Leidel, Nils
    Dau, Holger
    Haumann, Michael
    Gagliardi, Laura
    Cramer, Christopher J.
    Llobet, Antoni
    Electronic Structure of Oxidized Complexes Derived from cis-Ru(II)(bpy)(2)(H(2)O)(2)](2+) and Its Photoisomerization Mechanism2011In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 50, no 21, p. 11134-11142Article in journal (Refereed)
    Abstract [en]

    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)(0)](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.

  • 29.
    Shevchenko, Denys
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Anderlund, Magnus F.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Thapper, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Photochemical water oxidation with visible light using a cobalt containing catalyst2011In: Energy and Environmental Science, ISSN 1754-5692, Vol. 4, no 4, p. 1284-1287Article in journal (Refereed)
    Abstract [en]

    Artificial photosynthesis aims at using solar light energy to oxidatively split water to oxygen, protons and electrons and store the energy in a chemical fuel. Here we present a cobalt phosphonate material that can split water catalytically, driven by visible light in aqueous solutions of pH 7.

  • 30.
    Streich, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Karnahl, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Astuti, Yeni
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Cady, Clyde W.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Comparing the Reactivity of Benzenedithiolate- versus Alkyldithiolate-Bridged Fe2(CO)6 Complexes with Competing Ligands2011In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 7, p. 1106-1111Article in journal (Refereed)
    Abstract [en]

    The reactivity of [(mu-X(2)bdt)Fe-2(CO)(6)] [(bdt)1, X(2)bdt = 3,6-di-substituted bezenedithiolate; X = H, Cl] with ligands of different donor strengths is investigated and compared to that of [(mu-pdt)Fe-2(CO)(6)] [(pdt) 1, pdt = propyldithiolate] and [(mu-edt)Fe-2(CO)(6)] [(edt)1, edt = ethyldithiolate]. Strong donor ligands (L = CN-, PMe3) when added to (bdt) 1 lead to mononuclear [(bdt)Fe(L)(2)(CO)(2)], (bdt)6(L), in a disproportionation and fragmentation reaction, while simple ligand-substitution reactions occur on (edt)1 and (pdt)1 under identical conditions. In the presence of weaker ligands such as secondary amines or dmf, the alkyldithiolate-bridged complexes are unreactive, while (bdt)1 transforms to an O-2-sensitive, magnetically uncoupled species, potentially a mononuclear Fe-I complex coordinated by bdt and at least 2 CO ligands.

  • 31.
    Öberg, Elisabet
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Geng, Xue-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Santoni, Marie-Pierre
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    C,C-Diacetylenic phosphaalkenes in palladium-catalyzed cross-coupling reactions2011In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 9, no 18, p. 6246-6255Article in journal (Refereed)
    Abstract [en]

    The reactivity of bis-TMS-substituted C,C-diacetylenic phosphaalkene (A(2)PA) 1 in Sonogashira-Hagihara cross-coupling reactions has been examined. The selective and successive deprotection of the two silyl groups in 1 is enabled by the steric bulk of the Mes* group which renders the acetylene trans to Mes* more reactive and thereby facilitates selective and consecutive couplings with iodoarenes. In situ transformation of the TMS-protected acetylenes into Cu(I)acetylides is the key step in the synthetic sequence and enables the preparation of the first dimeric A(2)PA linked by a phenylene spacer. cis-trans Isomerization across the P = C bond is triggered by a tertiary amine and exclusively observed in the case of nitrophenyl-substituted A(2)PAs. The introduced aryl groups are integral parts of the entire p-system as evidenced by spectroscopic and electrochemical studies.

1 - 31 of 31
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