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  • 1.
    Ahlford, Katrin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ekström, Jesper
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zaitsev, Alexey B.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ryberg, Per
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Asymmetric Transfer Hydrogenation of Ketones Catalyzed by Amino Acid Derived Rhodium Complexes: On the Origin of Enantioselectivity and Enantioswitchability2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 42, p. 11197-11209Article in journal (Refereed)
    Abstract [en]

    Amino acid based thioamides, hydroxamic acids, and hydrazides have been evaluated as ligands in the rhodium-catalyzed asymmetric transfer hydrogenation of ketones in 2-propanol. Catalysts containing thioamide ligands derived from L-valine were found to selectively generate the product with an R configuration (95 % ee), whereas the corresponding L-valine-based hydroxamic acids or hydrazides facilitated the formation of the (S)-alcohols (97 and 91 % ee, respectively). The catalytic reduction was examined by performing a structure–activity correlation investigation with differently functionalized or substituted ligands and the results obtained indicate that the major difference between the thioamide and hydroxamic acid based catalysts is the coordination mode of the ligands. Kinetic experiments were performed and the rate constants for the reduction reactions were determined by using rhodium–arene catalysts derived from amino acid thioamide and hydroxamic acid ligands. The data obtained show that the thioamide-based catalyst systems demonstrate a pseudo-first-order dependence on the substrate, whereas pseudo-zero-order dependence was observed for the hydroxamic acid containing catalysts. Furthermore, the kinetic experiments revealed that the rate-limiting steps of the two catalytic systems differ. From the data obtained in the structure–activity correlation investigation and along with the kinetic investigation it was concluded that the enantioswitchable nature of the catalysts studied originates from different ligand coordination, which affects the rate-limiting step of the catalytic reduction reaction.

  • 2.
    Andersson, Linnéa
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry. Oorganisk kemi.
    Exploring expandable microspheres as a novel pore former in gel-cast macroporous alumina2008Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Expandable microspheres have been explored as sacrificial templates for the production of macroporous ceramics. Concentrated alumina powder suspensions that contain expandable microspheres have been consolidated by gel-casting. The temperature range for the setting of the monomers and cross-linkers in the gel-casting system was tailored to allow the gas-filled polymer spheres to expand before the surrounding powder body became rigid. It has been demonstrated that it is possible to tune and tailor the porosity up to 86 % and the pore size distribution from 15 up to 150 micrometers by controlling the amount and size of the expandable microspheres. Scanning electron microscopy showed that the porosity became more and more open as the total porosity increased. This was corroborated by a preliminary study by X-ray µ Computed Tomography, which showed a very high connectivity between the pores, in a macroporous alumina body with a high porosity. The connectivity was reduced when alumina particles were deposited as a homogenous coating of on the expandable microspheres by a layer-by-layer coating process. The expandable microspheres has the advantage that a relatively low amount of organic material results in a large pore volume, which allow rapid and facile burn-out. It was demonstrated that the temperature induced expansion of the microspheres, and the associated increase of the suspension volume could be used as a novel casting method to yield macroporous alumina bodies with complex shapes. Ceramics produced with this method could find application ranging from bone scaffolds to low mass kiln furniture.

  • 3.
    Andersson, Nina
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Mesostructured materials: Synthesis towards applications2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A new class of materials with well-defined structures on mesoscopic (2-50 nm) length scales has attracted considerable interest during the last decade. These mesostructured mataterials are formed from the self-assembly of amphiphillic molecules and inorganic precursors. The aim of this thesis has been to develop preparation methods that are scalable, and at the same time allow for efficient structural control coupled with possibility to incorporate different functionalities.

    Two different industrial processes for production of particles with spherical morphology were successfully tailored for synthesis of well-ordered mesostructured particles. An existing spray drying method for a fast and continuous production was further developed, and for the first time, an emulsion-based method was implemented. The latter method resulted in superior control of both particle size and internal mesostructure.

    Mesostructured photochromic pigments were synthesised by incorporating photochromic dyes in the organic domains of the surfactant templated inorganic/organic mesostructured silica particles. The pigments were produced using a one-pot synthesis method employing an aerosol reactor, allowing control over both the internal mesostructure and the dye content. We show that transparent photochromic films can be prepared using latex binders and conventional coating technology.

    Mesoporous magnetic carrier materials were prepared by adding iron oxide nanoparticles during either the emulsion- or aerosol processing. The surfactant templated silica matrix displayed well-ordered internal pore architecture with limited pore blocking caused by the incorporated iron oxide nanoparticles. The iron oxide content was precisely controlled, and the magnetic properties were preserved during the processing. Finally we demonstrate that these materials can be used to magnetically separate water-soluble dyes from solution.

  • 4.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hammar, Peter
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Himo, Fahmi
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective organocatalytic hydrophosphination of alpha,beta-unsaturated aldehydes2007In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 46, p. 4507-4510Article in journal (Refereed)
  • 5. Pan, Qinhe
    et al.
    Li, Jiyang
    Christensen, Kirsten Elvira
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Bonneau, Charlotte
    Ren, Xiaoyan
    Shi, Lei
    Zou, Xiaodong
    Li, Guanghua
    Yu, Jihong
    Xu, Ruren
    A germanate built from from 68126 cavity co-templated by a (H2O)16 water cluster and 2-methylpiperazine2008In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773Article in journal (Refereed)
  • 6.
    Sundén, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ibrahem, Ismail
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A highly enantioselective catalytic domino aza-Michael/aldol reaction: one-pot organocatalytic asymmetric synthesis of 1,2-dihydroquinolidines2007In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 349, p. 827-832Article in journal (Refereed)
  • 7.
    Ullah, Farman
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Deiana, Luca
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhu, Mingzhao
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ibrahem, Ismail
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hammar, Peter
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Department of Structural Chemistry. Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective organocatalytic conjugate addition of fluorocarbon nucleophiles to α,β-unsaturated aldehydes2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 39, p. 10013-10017Article in journal (Refereed)
    Abstract [en]

    A highly chemo- and enantioselective organocatalytic addition of fluorocarbon nucleophiles, such as 1-fluoro-bis(phenylsulfonyl)methane, toα,β-unsaturated aldehydes is presented (see scheme). The reactions are catalyzed by simple chiral amines and give access to optically active fluorine derivatives in good yields and up to 95 % ee. Notably, the methodology can be applied to the formation of a chiral quaternary carbon center bearing a fluorine atom with high enantioselectivity.

  • 8.
    Weber, Jens
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Impact of cross-linking density and glassy chain dynamics on pore stability in mesoporous poly(styrene)2009In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 42, no 21, p. 8234-8240Article in journal (Refereed)
    Abstract [en]

    Mesoporous poly(styrene) (PS) containing various amounts of the cross-linker divinylbenzene was synthesized by a hard-templating routine using pressed pellets of fumed silica as templates. Porous polymers with a surface area of 215 m2g-1 and porosities up to ~35 vol.-% could be obtained. The impact of the cross-linker content and the processing on the porosity of the materials was investigated by nitrogen sorption and small angle X-ray scattering. The surface area of the nascent porous PS increases and the pore size decrease with increasing amount of cross-linker. Furthermore, it was found that the porous polymers loose surface area at temperatures that are substantially below the glass transition temperature, Tg, of bulk polystyrene. The loss in surface area at temperatures below 65°C suggests that partial pore collapse also may be induced in the glassy state. Finally, the stability of the mesopores against solvent swelling was investigated. A critical pore collapse was found at a cross-linker content of ~ 20 wt.-%. In this context, also the existence of traced porosity, i.e. a non accessible mesostructure or porosity, could be confirmed.

1 - 8 of 8
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