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  • 1.
    Brown, Allison
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Antila, Liisa
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Mirmohades, Mohammad
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Pullen, Sonja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ultrafast Electron Transfer between Dye and Catalyst on a Mesoporous NiO Surface2016In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 26, p. 8060-8063Article in journal (Other academic)
    Abstract [en]

    The combination of molecular dyes and catalysts with semiconductors into dye-sensitized solar fuel devices (DSSFDs) requires control of efficient interfacial and surface charge transfer between the components. The present study reports on the light-induced electron transfer processes of p-type NiO films cosensitized with coumarin C343 and a bioinspired proton reduction catalyst, [FeFe](mcbdt)(CO)(6) (mcbdt = 3-carboxybenzene-1,2-dithiolate). By transient optical spectroscopy we find that ultrafast interfacial electron transfer (tau approximate to 200 fs) from NiO to the excited C343 ("hole injection") is followed by rapid (t(1/2) approximate to 10 ps) and efficient surface electron transfer from C343 to the coadsorbed [FeFe] (mcbdt)(CO)(6). The reduced catalyst has a clear spectroscopic signature that persists for several tens of microseconds, before charge recombination with NiO holes occurs. The demonstration of rapid surface electron transfer from dye to catalyst on NiO, and the relatively long lifetime of the resulting charge separated state, suggests the possibility to use these systems for photocathodes on. DSSFDs.

  • 2. Fei, Honghan
    et al.
    Pullen, Sonja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Wagner, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Cohen, Seth M.
    Functionalization of robust Zr(IV)-based metal-organic framework films via a postsynthetic ligand exchange2015In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, no 1, p. 66-69Article in journal (Refereed)
    Abstract [en]

    A facile and efficient fabrication approach for homogeneous, crack-free UiO-66 films with exceptionally high crystallinity and tunable thickness on a transparent and conductive glass substrate is reported. Two functionalized species, a catechol ligand and a Fe-2 complex with structural resemblance to the active site of [FeFe] hydrogenase, were introduced into the MOF films via a postsynthetic exchange. Voltammetric studies show the [FeFe] complex in the thinner UiO-66 films (2-5 mu m) can be reduced electrochemically.

  • 3.
    Gilbert Gatty, Mélina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Pullen, Sonja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Sheibani, E.
    Royal Inst Technol, Dept Chem Chem Sci & Engn, KTH, Organ Chem, S-10044 Stockholm, Sweden;Univ Ishafan, Dept Chem, Ishafan 8174673441, Iran.
    Tian, Haining
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Direct evidence of catalyst reduction on dye and catalyst co-sensitized NiO photocathodes by mid-infrared transient absorption spectroscopy2018In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 9, no 22, p. 4983-4991Article in journal (Refereed)
    Abstract [en]

    Co-sensitization of molecular dyes and catalysts on semiconductor surfaces is a promising strategy to build photoelectrodes for solar fuel production. In such a photoelectrode, understanding the charge transfer reactions between the molecular dye, catalyst and semiconductor material is key to guide further improvement of their photocatalytic performance. Herein, femtosecond mid-infrared transient absorption spectroscopy is used, for the first time, to probe charge transfer reactions leading to catalyst reduction on co-sensitized nickel oxide (NiO) photocathodes. The NiO films were co-sensitized with a molecular dye and a proton reducing catalyst from the family of [FeFe](bdt)(CO)(6) (bdt = benzene-1,2-dithiolate) complexes. Two dyes were used: an organic push-pull dye denoted E2 with a triarylamine-oligothiophene-dicyanovinyl structure and a coumarin 343 dye. Upon photo-excitation of the dye, a clear spectroscopic signature of the reduced catalyst is observed a few picoseconds after excitation in all co-sensitized NiO films. However, kinetic analysis of the transient absorption signals of the dye and reduced catalyst reveal important mechanistic differences in the first reduction of the catalyst depending on the co-sensitized molecular dye (E2 or C343). While catalyst reduction is preceded by hole injection in NiO in C343-sensitized NiO films, the singly reduced catalyst is formed by direct electron transfer from the excited dye E2* to the catalyst in E2-sensitized NiO films. This change in mechanism also impacts the lifetime of the reduced catalyst, which is only ca. 50 ps in E2-sensitized NiO films but is >5 ns in C343-sensitized NiO films. Finally, the implication of this mechanistic study for the development of better co-sensitized photocathodes is discussed.

  • 4.
    Hammarström, Leif
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Brown, Allison
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Mirmohades, Mohammad
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Pullen, Sonja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Mechanistic investigations and detection of intermediates of molecular proton reduction catalysts2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, article id 95-INORArticle in journal (Other academic)
  • 5.
    Hammarström, Leif
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Brown, Allison
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Zhang, Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    d'Amario, Luca
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Föhlinger, Jens
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Maji, Somnath
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Pullen, Sonja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Dye-sensitized NiO as p-type photocathode for photovoltaic and solar fuels devices2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, article id 77-ENVRArticle in journal (Other academic)
  • 6.
    Karnahl, Michael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Tschierlei, Stefanie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Erdem, Oezlen F.
    Pullen, Sonja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Santoni, Marie-Pierre
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Reijerse, Edward J.
    Lubitz, Wolfgang
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mixed-valence [(FeFeII)-Fe-I] hydrogenase active site model complexes stabilized by a bidentate carborane bis-phosphine ligand2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 40, p. 12468-12477Article in journal (Refereed)
    Abstract [en]

    A series of [FeFe]-hydrogenase active site analogues, with the general formula [Fe-2(dt)(CO)(4)(BC)] 1-3 (dt = dithiolate, pdt = propyl-1,3-dt (1), bdt = benzene-1,2-dt (2), edt = ethyl-1,2-dt (3); BC = 1,2-bisdiphenylphosphine-1,2-o-carborane), has been prepared and structurally characterized. While the electrochemical reductions of 1-3 are largely invariant to the different nature of their dt bridges, the oxidations differ by more than 120 mV in between the series. Remarkably, all three compounds are reversibly oxidized, with complex 1 that contains the most electron-donating pdt ligand at the mildest potential of -0.09 V vs. Fc/Fc(+). The one-electron oxidized state 1(ox) is stable for several minutes and was spectroscopically characterized by FTIR and EPR. EPR spectroscopy provided evidence that in the mixed-valence [(FeFeII)-Fe-I] state most of the spin density is located on the iron with the BC-ligand. This is monitored through the strong P-31 hyperfine coupling of the phenyl groups of the BC ligand, while further delocalization into the o-carborane unit is negligible.

  • 7.
    Mijangos, Edgar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Roy, Souvik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Pullen, Sonja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Evaluation of two- and three-dimensional electrode platforms for the electrochemical characterization of organometallic catalysts incorporated in non-conducting metal-organic frameworks2017In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, no 15, p. 4907-4911Article in journal (Refereed)
    Abstract [en]

    The development of a reliable platform for the electrochemical characterization of a redox-active molecular diiron complex, [FeFe], immobilized in a non-conducting metal organic framework (MOF), UiO-66, based on glassy-carbon electrodes is reported. Voltammetric data with appreciable current responses can be obtained by the use of multiwalled carbon nanotubes (MWCNT) or mesoporous carbon (CB) additives that function as conductive scaffolds to interface the MOF crystals in "three-dimensional" electrodes. In the investigated UiO-66-[FeFe] sample, the low abundance of [FeFe] in the MOF and the intrinsic insulating properties of UiO-66 prevent charge transport through the framework, and consequently, only [FeFe] units that are in direct physical contact with the electrode material are electrochemically addressable.

  • 8.
    Morales Salazar, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mijangos, Edgar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Pullen, Sonja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Gao, Ming
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Functional small-molecules & polymers containing P[double bond, length as m-dash]C and As[double bond, length as m-dash]C bonds as hybrid π-conjugated materials2017In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 53, no 6, p. 1120-1123Article in journal (Refereed)
    Abstract [en]

    Stable phospha- and arsaalkenes were used to synthesize polymers containing unsaturated P[double bond, length as m-dash]C and As[double bond, length as m-dash]C moieties. The composition, chemical environment, structure, optical, and electronic properties of the monomers and polymers were elucidated. The incorporation of the heteroatom-carbon double bonded units efficiently perturbs the optoelectronics and solid state features of both monomeric and polymeric scaffolds. Proof-of principle work supports their responsive character through post-functionalisation and electrochromic behaviour. To the best of our knowledge, this is the first example of a polymer containing arsenic-carbon double bonds.

  • 9. Nishida, Jun
    et al.
    Tamimi, Amr
    Fei, Honghan
    Pullen, Sonja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Cohen, Seth M.
    Fayer, Michael D.
    Structural dynamics inside a functionalized metal-organic framework probed by ultrafast 2D IR spectroscopy2014In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 111, no 52, p. 18442-18447Article in journal (Refereed)
    Abstract [en]

    The structural elasticity of metal-organic frameworks (MOFs) is a key property for their functionality. Here, we show that 2D IR spectroscopy with pulse-shaping techniques can probe the ultrafast structural fluctuations of MOFs. 2D IR data, obtained from a vibrational probe attached to the linkers of UiO-66 MOF in low concentration, revealed that the structural fluctuations have time constants of 7 and 670 ps with no solvent. Filling the MOF pores with dimethylformamide (DMF) slows the structural fluctuations by reducing the ability of the MOF to undergo deformations, and the dynamics of the DMF molecules are also greatly restricted. Methodology advances were required to remove the severe light scattering caused by the macroscopic-sizedMOF particles, eliminate interfering oscillatory components from the 2D IR data, and address Forster vibrational excitation transfer.

  • 10.
    Pavliuk, Mariia V.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Cieślak,, A. M.
    Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland.
    Abdellah, Mohamed
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström. South Valley Univ, Qena Fac Sci, Dept Chem, Qena 83523, Egypt.
    Budinská, Alena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Pullen, Sonja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Sokolowski, K.
    Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland.
    Fernandes, Daniel L. A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Szlachetko, J.
    Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland.
    Bastos, E. L
    Univ Sao Paulo, Inst Chem, Dept Fundamental Chem, BR-05508000 Sao Paulo, Brazil.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lewinski, J.
    Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland; Warsaw Univ Technol, Fac Chem, PL-00661 Warsaw, Poland.
    Sá, Jacinto
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland.
    Hydrogen evolution with nanoengineered ZnO interfaces decorated using a beetroot extract and a hydrogenase mimic2017In: Sustainable Energy & Fuels, ISSN 2398-4902, Vol. 1, p. 69-73Article in journal (Refereed)
    Abstract [en]

    Herein, we report a nano-hybrid photo-system based on abundant elements for H2 production with visible light. The photo-system's proficiency relates to the novel ZnO nanocrystals employed. The ZnO carboxylate oligoethylene glycol shell enhances charge separation and accumulates reactive electrons for the photocatalytic process. 

  • 11.
    Pavliuk, Mariia V.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Taras Shevchenko Natl Univ Kyiv, Dept Inorgan Chem, Volodymyrska St 64-13, UA-01601 Kiev, Ukraine.
    Mijangos, Edgar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Makhankova, Valeriya G.
    Taras Shevchenko Natl Univ Kyiv, Dept Inorgan Chem, Volodymyrska St 64-13, UA-01601 Kiev, Ukraine.
    Kokozay, Vladimir N.
    Taras Shevchenko Natl Univ Kyiv, Dept Inorgan Chem, Volodymyrska St 64-13, UA-01601 Kiev, Ukraine.
    Pullen, Sonja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Liu, Jia
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Zhu, Jie-Fang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Thapper, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Homogeneous Cobalt/Vanadium Complexes as Precursors for Functionalized Mixed Oxides in Visible-Light-Driven Water Oxidation2016In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 9, no 20, p. 2957-2966Article in journal (Refereed)
    Abstract [en]

    The heterometallic complexes (NH4)2[Co(H2O)6]2[V10O28]·4H2O (1) and (NH4)2[Co(H2O)5(β-HAla)]2[V10O28]·4H2O (2) have been synthesized and used for the preparation of mixed oxides as catalysts for water oxidation. Thermal decomposition of 1 and 2 at relatively low temperatures (<500 °C) leads to the formation of the solid mixed oxides CoV2O6/V2O5 (3) and Co2V2O7/V2O5 (4). The complexes (1, 2) and heterogeneous materials (3, 4) act as catalysts for photoinduced water oxidation. A modification of the thermal decomposition procedure allowed the deposition of mixed metal oxides (MMO) on a mesoporous TiO2 film. The electrodes containing Co/V MMOs in TiO2 films were used for electrocatalytic water oxidation and showed good stability and sustained anodic currents of about 5 mA cm−2 at 1.72 V versus relative hydrogen electrode (RHE). This method of functionalizing TiO2 films with MMOs at relatively low temperatures (<500 °C) can be used to produce other oxides with different functionality for applications in, for example, artificial photosynthesis.

  • 12.
    Pullen, Sonja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mimicking the Outer Coordination Sphere in [FeFe]-Hydrogenase Active Site Models: From Extended Ligand Design to Metal-Organic Frameworks2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Biomimetic catalysis is an important research field, as a better understanding of nature´s powerful toolbox for the conversion of molecules can lead to technological progress. [FeFe]-hydrogenases are very efficient catalysts for hydrogen production. These enzymes play a crucial role in the metabolism of green algae and certain cyanobacteria. Their active site consists of a diiron complex that is embedded in an interactive protein matrix.

    In this thesis, two pathways for mimicking the outer coordination sphere effects resulting from the protein matrix are explored.

    The first is the construction of model complexes containing phosphine ligands that are coordinated to the iron center as well as covalently linked to the bridging ligand of the complex. The effect of such linkers is an increased energy barrier for the rotation of the Fe(CO2)(PL3)-subunit, which potentially could stabilize a terminal hydride that is an important intermediate in the proton reduction cycle.

    The second pathway follows the incorporation of [FeFe]-hydrogenase active site model complexes into metal-organic frameworks (MOFs). Resulting MOF-catalysts exhibit increased photocatalytic activity compared to homogenous references due to a stabilizing effect on catalytic intermediates by the surrounding framework. Catalyst accessibility within the MOF and the influence of the framework on chemical reactivity are examined in the work presented. Furthermore, an initial step towards application of MOF-catalysts in a device was made by interfacing them with electrodes.

    The work of this thesis highlights strategies for the improvement of biomimetic model catalysts and the knowledge gained can be transferred to other systems mimicking the function of enzymes. 

    List of papers
    1. Direct Observation of Key Catalytic Intermediates in a Photoinduced Proton Reduction Cycle with a Diiron Carbonyl Complex
    Open this publication in new window or tab >>Direct Observation of Key Catalytic Intermediates in a Photoinduced Proton Reduction Cycle with a Diiron Carbonyl Complex
    Show others...
    2014 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, no 50, p. 17366-17369Article in journal (Refereed) Published
    Abstract [en]

    The structure and reactivity of intermediatesin the photocatalytic cycle of a proton reductioncatalyst, [Fe2(bdt)(CO)6] (bdt = benzenedithiolate), wereinvestigated by time-resolved spectroscopy. The singlyreduced catalyst [Fe2(bdt)(CO)6]−, a key intermediate inphotocatalytic H2 formation, was generated by reactionwith one-electron reductants in laser flash-quench experimentsand could be observed spectroscopically on thenanoseconds to microseconds time scale. From UV/visand IR spectroscopy, [Fe2(bdt)(CO)6]− is readilydistinguished from the two-electron reduced catalyst[Fe2(bdt)(CO)6]2− that is obtained inevitably in theelectrochemical reduction of [Fe2(bdt)(CO)6]. For thedisproportionation rate constant of [Fe2(bdt)(CO)6]−, anupper limit on the order of 107 M−1 s−1 was estimated,which precludes a major role of [Fe2(bdt)(CO)6]2− inphotoinduced proton reduction cycles. Structurally [Fe2-(bdt)(CO)6]− is characterized by a rather asymmetricallydistorted geometry with one broken Fe−S bond and sixterminal CO ligands. Acids with pKa ≤ 12.7 protonate[Fe2(bdt)(CO)6]− with bimolecular rate constants of 4 ×106, 7 × 106, and 2 × 108 M−1 s−1 (trichloroacetic,trifluoroacetic, and toluenesulfonic acids, respectively).The resulting hydride complex [Fe2(bdt)(CO)6H] istherefore likely to be an intermediate in photocatalyticcycles. This intermediate resembles structurally andelectronically the parent complex [Fe2(bdt)(CO)6], withvery similar carbonyl stretching frequencies.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2014
    National Category
    Physical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-240552 (URN)10.1021/ja5085817 (DOI)000346682600003 ()
    Available from: 2015-01-07 Created: 2015-01-07 Last updated: 2017-12-05
    2. Restricted Rotation of an Fe(CO)2(PL3)-subunit in [FeFe ]-Hydrogenase Active Site Mimics by Tethering Phosphine Ligands
    Open this publication in new window or tab >>Restricted Rotation of an Fe(CO)2(PL3)-subunit in [FeFe ]-Hydrogenase Active Site Mimics by Tethering Phosphine Ligands
    (English)Manuscript (preprint) (Other academic)
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-318973 (URN)
    Available from: 2017-03-29 Created: 2017-03-29 Last updated: 2017-03-30
    3. Enhanced Photochemical Hydrogen Production by a Molecular Diiron Catalyst Incorporated into a Metal-Organic Framework
    Open this publication in new window or tab >>Enhanced Photochemical Hydrogen Production by a Molecular Diiron Catalyst Incorporated into a Metal-Organic Framework
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    2013 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 45, p. 16997-17003Article in journal (Refereed) Published
    Abstract [en]

    A molecular proton reduction catalyst [FeFe](dcbdt)(CO)(6) (1, dcbdt = 1,4-dicarboxylbenzene-2,3-dithiolate) with structural similarities to [FeFe]-hydrogenase active sites has been incorporated into a highly robust Zr(IV)-based metal-organic framework (MOF) by postsynthetic exchange (PSE). The PSE protocol is crucial as direct solvothermal synthesis fails to produce the functionalized MOF. The molecular integrity of the organometallic site within the MOF is demonstrated by a variety of techniques, including X-ray absorption spectroscopy. In conjunction with [Ru(bpy)(3)](2+) as a photosensitizer and ascorbate as an electron donor, MOF-[FeFe](dcbdt)(CO)(6) catalyzes photochemical hydrogen evolution in water at pH 5. The immobilized catalyst shows substantially improved initial rates and overall hydrogen production when compared to a reference system of complex 1 in solution. Improved catalytic performance is ascribed to structural stabilization of the complex when incorporated in the MOF as well as the protection of reduced catalysts 1(-) and 1(2-) from undesirable charge recombination with oxidized ascorbate.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-212862 (URN)10.1021/ja407176p (DOI)000327103600042 ()
    Available from: 2013-12-17 Created: 2013-12-16 Last updated: 2017-12-06Bibliographically approved
    4. Catalyst accessibility to chemical reductants in metal–organic frameworks
    Open this publication in new window or tab >>Catalyst accessibility to chemical reductants in metal–organic frameworks
    Show others...
    2017 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 53, no 22, p. 3257-3260Article in journal (Refereed) Published
    Abstract [en]

    A molecular H2-evolving catalyst, [Fe2(cbdt)(CO)6] ([FeFe], cbdt = 3-carboxybenzene-1,2-dithiolate), has been attached covalently to an amino-functionalized MIL-101(Cr) through an amide bond. Chemical reduction experiments reveal that the MOF channels can be clogged by ion pairs that are formed between the oxidized reductant and the reduced catalyst. This effect is lessened in MIL-101-NH-[FeFe] with lower [FeFe] loadings. On longer timescales, it is shown that large proportions of the [FeFe] catalysts within the MOF engage in photochemical hydrogen production and the amount of produced hydrogen is proportional to the catalyst loading.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-318972 (URN)10.1039/c7cc00022g (DOI)000398998500023 ()28261731 (PubMedID)
    Available from: 2017-03-29 Created: 2017-03-29 Last updated: 2017-12-28Bibliographically approved
    5. Functionalization of robust Zr(IV)-based metal-organic framework films via a postsynthetic ligand exchange
    Open this publication in new window or tab >>Functionalization of robust Zr(IV)-based metal-organic framework films via a postsynthetic ligand exchange
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    2015 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, no 1, p. 66-69Article in journal (Refereed) Published
    Abstract [en]

    A facile and efficient fabrication approach for homogeneous, crack-free UiO-66 films with exceptionally high crystallinity and tunable thickness on a transparent and conductive glass substrate is reported. Two functionalized species, a catechol ligand and a Fe-2 complex with structural resemblance to the active site of [FeFe] hydrogenase, were introduced into the MOF films via a postsynthetic exchange. Voltammetric studies show the [FeFe] complex in the thinner UiO-66 films (2-5 mu m) can be reduced electrochemically.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-241388 (URN)10.1039/c4cc08218d (DOI)000345909400008 ()25364799 (PubMedID)
    Available from: 2015-01-26 Created: 2015-01-12 Last updated: 2017-12-05Bibliographically approved
    6. [FeFe] Hydrogenase Active Site Model Chemistry in a UiO-66 Metal-Organic Framework
    Open this publication in new window or tab >>[FeFe] Hydrogenase Active Site Model Chemistry in a UiO-66 Metal-Organic Framework
    (English)Article in journal (Refereed) Submitted
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-318974 (URN)
    Available from: 2017-03-29 Created: 2017-03-29 Last updated: 2017-03-30
  • 13.
    Pullen, Sonja
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Brinkert, Katharina
    SolEn for a Sustainable Future: Developing and Teaching a Multidisciplinary Course on Solar Energy To Further Sustainable Education in Chemistry2014In: Journal of Chemical Education, ISSN 0021-9584, E-ISSN 1938-1328, Vol. 91, no 10, p. 1569-1573Article in journal (Refereed)
    Abstract [en]

    The high demand for the integration of sustainable topics into university curricula presents new challenges for the way chemistry is traditionally taught. New teaching concepts are required that consider and connect different disciplines to achieve a higher student awareness of the importance of these topics for humanity, the environment, and the future of our planet. This article describes a uniquely multidisciplinary graduate course on solar energy; the course may serve as an example of how to incorporate sustainable topics into chemistry programs, and as a starting point from which to build for others. It combines different scientific, industrial, political, and humanitarian approaches to the topic and provides a broad overview of one of the main future energy resources. New teaching methods are introduced, combined, and evaluated with respect to their effectiveness for a sustainable education within science and, in particular, chemistry. The success of this new course concept is demonstrated by high student satisfaction in a trial course evaluation and impressive exam results.

  • 14.
    Pullen, Sonja
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Fei, Honghan
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Cohen, Seth M.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Enhanced Photochemical Hydrogen Production by a Molecular Diiron Catalyst Incorporated into a Metal-Organic Framework2013In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 45, p. 16997-17003Article in journal (Refereed)
    Abstract [en]

    A molecular proton reduction catalyst [FeFe](dcbdt)(CO)(6) (1, dcbdt = 1,4-dicarboxylbenzene-2,3-dithiolate) with structural similarities to [FeFe]-hydrogenase active sites has been incorporated into a highly robust Zr(IV)-based metal-organic framework (MOF) by postsynthetic exchange (PSE). The PSE protocol is crucial as direct solvothermal synthesis fails to produce the functionalized MOF. The molecular integrity of the organometallic site within the MOF is demonstrated by a variety of techniques, including X-ray absorption spectroscopy. In conjunction with [Ru(bpy)(3)](2+) as a photosensitizer and ascorbate as an electron donor, MOF-[FeFe](dcbdt)(CO)(6) catalyzes photochemical hydrogen evolution in water at pH 5. The immobilized catalyst shows substantially improved initial rates and overall hydrogen production when compared to a reference system of complex 1 in solution. Improved catalytic performance is ascribed to structural stabilization of the complex when incorporated in the MOF as well as the protection of reduced catalysts 1(-) and 1(2-) from undesirable charge recombination with oxidized ascorbate.

  • 15.
    Pullen, Sonja
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. TU Dortmund Univ, Fac Chem & Chem Biol, Otto Hahn Str 6, D-44227 Dortmund, Germany.
    Maji, Somnath
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Indian Inst Technol Hyderabad, Dept Chem, Sangareddy 502285, Telangana, India.
    Stein, Matthias
    Max Planck Inst Dynam Complex Tech Syst, Sandtorstr 2, D-39106 Magdeburg, Germany.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Restricted rotation of an Fe(CO)(2)(PL3)-subunit in [FeFe]-hydrogenase active site mimics by intramolecular ligation2019In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 48, no 18, p. 5933-5939Article in journal (Refereed)
    Abstract [en]

    A new series of homodinuclear iron complexes as models of the [FeFe]-hydrogenase active site was prepared and characterized. The complexes of the general formula [Fe-2(mcbdt)(CO)(5)PPh2R] (mcbdt = benzene-1,2-dithiol-3-carboxylic acid) feature covalent tethers that link the mcbdt ligand with the phosphine ligands which are terminally coordinated to one of the Fe centres. The synthetic feasability of the concept is demonstrated with the preparation of three novel complexes. A detailed theoretical investigation showes that by introducing a rigid covalent link between the phosphine and the bridging dithiolate ligands, the rotation of the Fe(CO)(2)P unit is hindered and higher rotation barriers were calculated compared to non-linked reference complexes. The concept of restricting Fe(L)(3) rotation is an approach to kinetically stabilize terminal hydrides which are reactive intermediates in catalytic proton reduction cycles of the enzymes.

  • 16.
    Pullen, Sonja
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Photochemical Hydrogen Production with Metal-Organic Frameworks2016In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 59, no 19-20, p. 1712-1721Article in journal (Refereed)
    Abstract [en]

    Metal-Organic Frameworks (MOFs) have attracted increasing attention for the creation of solid-state platforms for catalysis applications. In this review article, we present strategies to employ MOF-based materials in photochemical hydrogen production. The scope ranges from the incorporation of single functions (catalyst or photosensitizer) to multifunctional MOFs that combine both light-harvesting and catalysis in one scaffold.

  • 17.
    Pullen, Sonja
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Roy, Souvik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    [FeFe] Hydrogenase active site model chemistry in a UiO-66metal-organic framework2017In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 53, no 37, p. 5227-5230Article in journal (Refereed)
    Abstract [en]

    The reactivity of [Fe-2(dcbdt)(CO)(6)] (1) confined in a UiO-66(Zr) metal-organic framework towards CO ligand substitutions with phosphines of different sizes was investigated. The reaction with smaller phosphines (PX3, X = Me, Et) is more selective compared to analogous reactions in homogenous solution phase, and two CO ligands at up to 80% of all [FeFe] sites in UiO-66-1 are replaced. The produced [Fe-2(dcbdt)(CO)(4)(PX3)(2)] complexes in the UiO-66 matrix behave like typical [FeFe] hydrogenase active site model complexes, are reduced at more cathodic potentials than their hexacarbonyl analogues, and form bridging hydrides under acidic conditions.

  • 18.
    Roy, Souvik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Pascanu, Vlad
    Pullen, Sonja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Gonzalez Miera, Greco
    Martin-Matute, Belén
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Catalyst accessibility to chemical reductants in metal–organic frameworks2017In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 53, no 22, p. 3257-3260Article in journal (Refereed)
    Abstract [en]

    A molecular H2-evolving catalyst, [Fe2(cbdt)(CO)6] ([FeFe], cbdt = 3-carboxybenzene-1,2-dithiolate), has been attached covalently to an amino-functionalized MIL-101(Cr) through an amide bond. Chemical reduction experiments reveal that the MOF channels can be clogged by ion pairs that are formed between the oxidized reductant and the reduced catalyst. This effect is lessened in MIL-101-NH-[FeFe] with lower [FeFe] loadings. On longer timescales, it is shown that large proportions of the [FeFe] catalysts within the MOF engage in photochemical hydrogen production and the amount of produced hydrogen is proportional to the catalyst loading.

  • 19. Wagner, Andreas
    et al.
    Pullen, Sonja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sasha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    The potential of ion beams for characterization of metal-organic frameworks2016Conference paper (Refereed)
    Abstract [en]

    Ion scattering has been employed for depth-profiling of metal organic frameworks (MOFs) to characterize the degree of post-synthetic uptake of [FeFe](mcbdt)(CO)(6) (mcbdt = 2,3-dithiolato-benzoic acid). The system investigated consisted of UiO-66 (UiO = University of Oslo) MOF thin films grown on p-type Si wavers in which a molecular proton reduction catalyst [FeFe](mcbdt)(CO)(6) was introduced by postsynthetic exchange (PSE). We have characterized samples by Rutherford Backscattering spectrometry (RBS), Time-of-Flight Elastic Recoil Detection analysis (TOF-ERDA) and by Time-of-Flight Medium Energy Ion Scattering (TOF-MEIS). The beam induced sample modification during the analysis has been characterized by Scanning Electron Microscopy (SEM). No detectable sample modification was found for RBS and TOF-MEIS whereas TOF-ERDA had a clear impact in the present experiment. Composition profiles could be obtained and indicated enrichment of catalyst and/or catalyst residual near to and at the sample surface.

1 - 19 of 19
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