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  • 1. Battistel, Marcos D.
    et al.
    Pendrill, Robert
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Freedberg, Daron I.
    Direct Evidence for Hydrogen Bonding in Glycans: A Combined NMR and Molecular Dynamics Study2013In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 117, no 17, p. 4860-4869Article in journal (Refereed)
    Abstract [en]

    We introduce the abundant hydroxyl groups of glycans as NMR handle's and structural probes to expand the repertoire of tools for structure function studies on glycans in solution. To this end, we present the facile detection and assignment of hydroxyl groups in a Wide range of sample concentrations (0.5-1700 mM) and temperatures, ranging from -5 to 25 degrees C.,We then exploit this information to directly detect hydrogen bonds, well-known for their importance in molecular structural determination through NMR. Via HSQC-TOCSY, we were able to determine the directionality; of these hydrogen bonds in sucrose Furthermore, by means Of molecular dynamics simulations in conjunction with NMR, we establish that one Out of the three detected hydrogen bonds arises from intermolecular interactions. This finding may shed light on glycan glycan interactions and glycan recognition by proteins.

  • 2. Dyson, P J
    et al.
    Laurenczy, G
    Ohlin, C A
    Vallance, J
    Welton, T
    Determination of hydrogen concentration in ionic liquids and the effect (or lack of) on rates of hydrogenation2003In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 19, p. 2418-2419Article in journal (Refereed)
    Abstract [en]

    The solubility of hydrogen and the corresponding Henry coefficients for 11 ionic liquids have been determined in situ at 100 atm H(2) pressure and are much lower than expected; attempts to correlate the solubility of hydrogen in the ionic liquids with the rate of reaction for the hydrogenation of benzene to cyclohexane in these solvents have been made.

  • 3.
    Emanuelsson, Rikard
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Conjugation in Organic Group 14 Element Compounds: Design, Synthesis and Experimental Evaluation2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis focuses on the chemical concept of conjugation, i.e., electron delocalization, and the effect it has on electronic and optical properties of molecules. The emphasis is on electron delocalization across a saturated σ-bonded segment, and in our studies these segments are either inserted between π-conjugated moieties or joined together to form longer chains. The electronic and optical properties of these compounds are probed and compared to those of traditionally π-conjugated compounds. The investigations utilize a combination of qualitative chemical bonding theories, quantum chemical calculations, chemical syntheses and different spectroscopic methods.

    Herein, it is revealed that a saturated σ-bonded segment inserted between two π-systems can have optical and electronic properties similar to a cross-conjugated compound when substituents with heavy Group 14 elements (Si, Ge or Sn) are attached to the central atom. We coined the terminology cross-hyperconjugation for this interaction, and have shown it by both computational and spectroscopic means. This similarity is also found in cyclic compounds, for example in the 1,4-disilacyclohexa-2,5-dienes, as we reveal that there is a cyclic aspect of cross-hyperconjugation. Cross-hyperconjugation can further also be found in smaller rings such as siloles and cyclopentadienes, and we show on the similarities between these and their cross-π-conjugated analogues, the fulvenes. Here, this concept is combined with that of excited state aromaticity and the electronic properties of these systems are rationalized in terms of “aromatic chameleon” effects. We show that the optical properties of these systems can be rationally tuned and predicted through the choice of substituents and knowledge about the aromaticity rules in both ground and excited states.

    We computationally examine the relation between conjugation and conductance and reveal that oligomers of 1,4-disilacyclohexa-2,5-dienes and related analogues can display molecular cord properties. The conductance through several σ-conjugated silicon compounds were also examined and show that mixed silicon and carbon bicyclo[2.2.2]octane compounds do not provide significant benefits over the open-chain oligosilanes. However, cyclohexasilanes, a synthetic precursor to the bicyclic compounds, displayed conformer-dependent electronic structure variations that were not seen for cyclohexanes. This allowed for computational design of a mechanically activated conductance switch.

  • 4.
    Halldin Stenlid, Joakim
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Computational Studies of Chemical Interactions: Molecules, Surfaces and Copper Corrosion2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The chemical bond – a corner stone in science and a prerequisite for life – is the focus of this thesis. Fundamental and applied aspects of chemical bonding are covered including the development of new computational methods for the characterization and rationalization of chemical interactions. The thesis also covers the study of corrosion of copper-based materials. The latter is motivated by the proposed use of copper as encapsulating material for spent nuclear fuel in Sweden.

    In close collaboration with experimental groups, state-of-the-art computational methods were employed for the study of chemistry at the atomic scale. First, oxidation of nanoparticulate copper was examined in anoxic aqueous media in order to better understand the copper-water thermodynamics in relation to the corrosion of copper material under oxygen free conditions. With a similar ambition, the water-cuprite interface was investigated with regards to its chemical composition and reactivity. This was compared to the behavior of methanol and hydrogen sulfide at the cuprite surface.

    An overall ambition during the development of computational methods for the analysis of chemical bonding was to bridge the gap between molecular and materials chemistry. Theory and results are thus presented and applied in both a molecular and a solid-state framework. A new property, the local electron attachment energy, for the characterization of a compound’s local electrophilicity was introduced. Together with the surface electrostatic potential, the new property predicts and rationalizes regioselectivity and trends of molecular reactions, and interactions on metal and oxide nanoparticles and extended surfaces.

    Detailed atomistic understanding of chemical processes is a prerequisite for the efficient development of chemistry. We therefore envisage that the results of this thesis will find widespread use in areas such as heterogeneous catalysis, drug discovery, and nanotechnology.

  • 5. Harper, James K.
    et al.
    Tishler, Derek
    Richardson, David
    Lokvam, John
    Pendrill, Robert
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Solid-State NMR Characterization of the Molecular Conformation in Disordered Methyl alpha-L-Rhamnofuranoside2013In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 117, no 26, p. 5534-5541Article in journal (Refereed)
    Abstract [en]

    A combination of solid-state C-13 NMR tensor data and DFT computational methods is utilized to predict the conformation in disordered methyl alpha-L-rhamnofuranoside. This previously uncharacterized solid is found to be crystalline and consists of at least six distinct conformations that exchange on the kHz time scale. A total of 66 model structures were evaluated, and six were identified as being consistent with experimental C-13 NMR data. All feasible structures have very similar carbon and oxygen positions and differ most significantly in OH hydrogen orientations. A concerted rearrangement of OH hydrogens is proposed to account for the observed dynamic disorder. This rearrangement is accompanied by smaller changes in ring conformation and is slow enough to be observed on the NMR time scale due to severe steric crowding among ring substituents. The relatively minor differences in non-hydrogen atom positions in the final structures suggest that characterization of a complete crystal structure by X-ray powder diffraction may be feasible.

  • 6.
    Hedenström, Mattias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johnels, Dan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Characterization of Hydrogenated Fullerenes by NMR Spectroscopy2010In: Fulleranes: The Hydrogenated Fullerenes / [ed] Franco Cataldo, Susana Iglesias-Groth, Dordrecht: Springer Netherlands, 2010, Vol. 2, p. 171-202Chapter in book (Other academic)
    Abstract [en]

    NMR spectroscopy is so far the only analytical technique that has been used to get a detailed structural characterization of hydrogenated fullerenes. A substantial amount of information derived from different NMR experiments can thus be found in the literature for a number of fullerenes hydrogenated to various degrees. These studies have benefitted from the fact that chemical shifts of H-1 and C-13 and in some cases also He-3 can be used to obtain structural information of these compounds. Such results, together with discussions about different NMR experiments and general considerations regarding sample preparations, are summarized in this chapter. The unique information, both structural and physicochemical, that can be derived from different NMR experiments ensures that this technique will continue to be of central importance in characterization of hydrogenated fullerenes.

  • 7.
    Huaiyu, Yang
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Crystallization of Parabens: Thermodynamics, Nucleation and Processing2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this work, the solubility of butyl paraben in 7 pure solvents and in 5 different ethanol-water mixtures has been determined from 1 ˚C to 50 ˚C. The solubility of ethyl paraben and propyl paraben in various solvents has been determined at 10 ˚C. The molar solubility of butyl paraben in pure solvents and its thermodynamic properties, measured by Differential Scanning Calorimetry, have been used to estimate the activity of the pure solid phase, and solution activity coefficients.

    More than 5000 nucleation experiments of ethyl paraben, propyl paraben and butyl paraben in ethyl acetate, acetone, methanol, ethanol, propanol and 70%, 90% ethanol aqueous solution have been performed. The induction time of each paraben has been determined at three different supersaturation levels in various solvents. The wide variation in induction time reveals the stochastic nature of nucleation. The solid-liquid interfacial energy, free energy of nucleation, nuclei critical radius and pre-exponential factor of parabens in these solvents have been determined according to the classical nucleation theory, and different methods of evaluation are compared. The interfacial energy of parabens in these solvents tends to increase with decreasing mole fraction solubility but the correlation is not very strong. The influence of solvent on nucleation of each paraben and nucleation behavior of parabens in each solvent is discussed. There is a trend in the data that the higher the boiling point of the solvent and the higher the melting point of the solute, the more difficult is the nucleation. This observation is paralleled by the fact that a metastable polymorph has a lower interfacial energy than the stable form, and that a solid compound with a higher melting point appears to have a higher solid-melt and solid-aqueous solution interfacial energy.

    It has been found that when a paraben is added to aqueous solutions with a certain proportion of ethanol, the solution separates into two immiscible liquid phases in equilibrium. The top layer is water-rich and the bottom layer is paraben-rich. The area in the ternary phase diagram of the liquid-liquid-phase separation region increases with increasing temperature. The area of the liquid-liquid-phase separation region decreases from butyl paraben, propyl paraben to ethyl paraben at the constant temperature.

    Cooling crystallization of solutions of different proportions of butyl paraben, water and ethanol have been carried out and recorded using the Focused Beam Reflectance Method, Particle Vision and Measurement, and in-situ Infrared Spectroscopy. The FBRM and IR curves and the PVM photos track the appearance of liquid-liquid phase separation and crystallization. The results suggest that the liquid-liquid phase separation has a negative influence on the crystal size distribution. The work illustrates how Process Analytical Technology (PAT) can be used to increase the understanding of complex crystallizations.

    By cooling crystallization of butyl paraben under conditions of liquid-liquid-phase separation, crystals consisting of a porous layer in between two solid layers have been produced. The outer layers are transparent and compact while the middle layer is full of pores. The thickness of the porous layer can reach more than half of the whole crystal. These sandwich crystals contain only one polymorph as determined by Confocal Raman Microscopy and single crystal X-Ray Diffraction. However, the middle layer material melts at lower temperature than outer layer material.

  • 8.
    Huang, Xiao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
    Conducting Redox Polymers for Electrode Materials: Synthetic Strategies and Electrochemical Properties2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Organic electrode materials represent an intriguing alternative to their inorganic counterparts due to their sustainable and environmental-friendly properties. Their plastic character allows for the realization of light-weight, versatile and disposable devices for energy storage. Conducting redox polymers (CRPs) are one type of the organic electrode materials involved, which consist of a π-conjugated polymer backbone and covalently attached redox units, the so-called pendant. The polymer backbone can provide conductivity while it is oxidized or reduced (i. e., p- or n-doped) and the concurrent redox chemistry of the pendant provides charge capacity. The combination of these two components enables CRPs to provide both high charge capacity and high power capability. This dyad polymeric framework provides a solution to the two main problems associated with organic electrode materials based on small molecules: the dissolution of the active material in the electrolyte, and the sluggish charge transport within the material. This thesis introduces a general synthetic strategy to obtain the monomeric CRPs building blocks, followed by electrochemical polymerization to afford the active CRPs material. The choice of pendant and of polymer backbone depends on the potential match between these two components, i.e. the redox reaction of the pendant and the doping of backbone occurring within the same potential region. In the thesis, terephthalate and polythiophene were selected as the pendant and polymer backbone respectively, to get access to low potential CRPs. It was found that the presence of a non-conjugated linker between polymer backbone and pendant is essential for the polymerizability of the monomers as well as for the preservation of individual redox activities. The resulting CRPs exhibited fast charge transport within the polymer film and low activation barriers for charge propagation. These low potential CRPs were designed as the anode materials for energy storage applications. The combination of redox active pendant as charge carrier and a conductive polymer backbone reveals new insights into the requirements of organic matter based electrical energy storage materials.

  • 9. Kearley, GJ
    et al.
    Johansson, P
    Uppsala University, Interfaculty Units, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, The Studsvik Neutron Research Laboratory. Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Delaplane, RG
    Physics, Department of Neutron Research. Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Lindgren, Jan
    Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. strukturkemi.
    Structure, dynamics and first principles study of diglyme as a model system for poly(ethyleneoxide), PEO2002In: Solid State Ionics: Diffusion & Reactions, Vol. 147, no 3,4, p. 237-Article in journal (Refereed)
  • 10. Kotsyubynskyy, Dmytro
    et al.
    Zerbetto, Mirco
    Šoltésová, Mária
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Charles University Prague .
    Engström, Olof
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pendrill, Robert
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kowalewski, Josef
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Polimeno, Antonin
    Stochastic Modeling of Flexible Biomolecules Applied to NMR Relaxation: 2. Interpretation of Complex Dynamics in Linear Oligosaccharides2012In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 116, no 50, p. 14541-14555Article in journal (Refereed)
    Abstract [en]

    A computational stochastic approach is applied to the description of flexible molecules. By combining (i) molecular dynamics simulations, (ii) hydrodynamics approaches, and (iii) a multidimensional diffusive description for internal and global dynamics, it is possible to build an efficient integrated approach to the interpretation of relaxation processes in flexible systems. In particular, the model is applied to the interpretation of nuclear magnetic relaxation measurements of linear oligosaccharides, namely a mannose-containing trisaccharide and the pentasaccharide LNF-1. Experimental data are reproduced with sufficient accuracy without free model parameters.

  • 11.
    Kuang, Guanglin
    et al.
    AlbaNova Univ Ctr, Sch Biotechnol, Royal Inst Technol KTH, Div Theoret Chem & Biol, S-10691 Stockholm, Sweden..
    Wang, Xu
    AlbaNova Univ Ctr, Sch Biotechnol, Royal Inst Technol KTH, Div Theoret Chem & Biol, S-10691 Stockholm, Sweden..
    Halldin, Christer
    Karolinska Inst, Ctr Psychiat Res, Dept Clin Neurosci, S-17176 Stockholm, Sweden..
    Nordberg, Agneta
    Karolinska Univ Hosp, Ctr Alzheimer Res Translat Alzheimer Neurobiol, Dept Neurobiol Care Sci & Soc, S-14186 Stockholm, Sweden..
    Långström, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
    Ågren, Hans
    AlbaNova Univ Ctr, Sch Biotechnol, Royal Inst Technol KTH, Div Theoret Chem & Biol, S-10691 Stockholm, Sweden..
    Tu, Yaoquan
    AlbaNova Univ Ctr, Sch Biotechnol, Royal Inst Technol KTH, Div Theoret Chem & Biol, S-10691 Stockholm, Sweden..
    Theoretical study of the binding profile of an allosteric modulator NS-1738 with a chimera structure of the alpha 7 nicotinic acetylcholine receptor2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 40, p. 28003-28009Article in journal (Refereed)
    Abstract [en]

    Potentiation of the function of the alpha 7 nicotinic acetylcholine receptor (alpha 7-nAChR) is believed to provide a possible way for the treatment of cholinergic system dysfunctions such as Alzheimer's disease and schizophrenia. Positive allosteric modulators (PAMs) are able to augment the peak current response of the endogenous agonist of alpha 7-nAChR by binding to some allosteric sites. In this study, the binding profile of a potent type I PAM, NS-1738, with a chimera structure (termed alpha 7-AChBP) constructed from the extracellular domain of alpha 7-nAChR and an acetylcholine binding protein was investigated with molecular docking, molecular dynamics simulation, and free energy calculation methods. We found that NS-1738 could bind to three allosteric sites of alpha 7-AChBP, namely, the top pocket, the vestibule pocket and the agonist sub-pocket. NS-1738 has moderate binding affinities (-6.76 to -9.15 kcal mol(-1)) at each allosteric site. The urea group is critical for binding and can form hydrogen-bond interactions with the protein. The bulky trifluoromethyl group also has a great impact on the binding modes and binding affinities. We believe that our study provides valuable insight into the binding profiles of type I PAMs with alpha 7-nAChR and is helpful for the development of novel PAMs.

  • 12.
    Mirmohades, Mohammad
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Towards a Novel Donor-Sensitizer-Catalyst Triad Entirely Composed of Earth Abundant Elements2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 13.
    Mohamed, Rana K.
    et al.
    Florida State Univ, Dept Chem & Biochem, Tallahassee, FL 32310 USA..
    Mondal, Sayantan
    Florida State Univ, Dept Chem & Biochem, Tallahassee, FL 32310 USA..
    Jorner, Kjell
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Delgado, Thais Faria
    Florida State Univ, Dept Chem & Biochem, Tallahassee, FL 32310 USA..
    Lobodin, Vladislav V.
    Natl High Magnet Field Lab, Tallahassee, FL 32310 USA.;Florida State Univ, Future Fuels Inst, Tallahassee, FL 32310 USA..
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Alabugin, Igor V.
    Florida State Univ, Dept Chem & Biochem, Tallahassee, FL 32310 USA..
    The Missing C-1-C-5 Cycloaromatization Reaction: Triplet State Antiaromaticity Relief and Self-Terminating Photorelease of Formaldehyde for Synthesis of Fulvenes from Enynes2015In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 137, no 49, p. 15441-15450Article in journal (Refereed)
    Abstract [en]

    The last missing example of the four archetypical cycloaromatizations of enediynes and enynes was discovered by combining a twisted alkene excited state with a new self-terminating path for intramolecular conversion of diradicals into closed-shell products. Photoexcitation of aromatic enynes to a twisted alkene triplet state creates a unique stereoelectronic situation, which is facilitated by the relief of excited state antiaromaticity of the benzene ring. This enables the usually unfavorable 5-endo-trig cyclization and merges it with 5-exo-dig closure. The 1,4-diradical product of the C1-C5 cyclization undergoes internal H atom transfer that is coupled with the fragmentation of an exocyclic C-C bond. This sequence provides efficient access to benzofulvenes from enynes and expands the utility of self-terminating aromatizing enyne cascades to photochemical reactions. The key feature of this self-terminating reaction is that, despite the involvement of radical species in the key cyclization step, no external radical sources or quenchers are needed to provide the products. In these cascades, both radical centers are formed transiently and converted to the closed-shell products via intramolecular H-transfer and C-C bond fragmentation. Furthermore, incorporating C-C bond cleavage into the photochemical self-terminating cyclizations of enynes opens a new way for the use of alkenes as alkyne equivalents in organic synthesis.

  • 14.
    Neimert-Andersson, Kristina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Somfai, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Stereoselective Synthesis of Polyhydroxyl Surfactants. Stereochemical Influence on Langmuir Monolayers2004In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 69, no 11, p. 3746-3752Article in journal (Refereed)
    Abstract [en]

    Herein is described the synthesis of surfactants featuring polyhydroxylated head groups. Three head groups were prepared via consecutive stereoselective dihydroxylations of a diene. By coupling of these with lipophilic tail groups six novel surfactants have been prepared. The monolayers prepared from four of these have been investigated at the air-water interface. Significant differences were observed between monolayers consisting of enantiomerically pure surfactants contra racemates as well as between diastereomers.

  • 15.
    Norgren, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Lignin: Recent advances and emerging applications2014In: Current Opinion in Colloid & Interface Science, ISSN 1359-0294, E-ISSN 1879-0399, Vol. 19, p. 409-416Article, review/survey (Refereed)
    Abstract [en]

    In this paper, we focus on the recent advances on the physical chemistry of lignin. Emerging trends of incorporating lignin in promising future applications such as controlled release, saccharification of lignocelluloses, bioplastics, composites, nanoparticles, adsorbents and dispersants, in electro-chemical applications and carbon fi bers, arealso reviewed. We briefl y describe the complexity of the lignin structure that influences the solution behavior, both as a macromolecule and a col loid, as well as the potential of being a renewable precursor in the development of high-value applications. Special attention is paid on summarizing the present knowledge on lignin colloidalstability and surface chemistry.

  • 16.
    Nozière, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A Kinetic and Mechanistic Study of the Amino Acid Catalyzed Aldol Condensation of Acetaldehyde in Aqueous and Salt Solutions2008In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 112, no 13, p. 2827-2837Article in journal (Refereed)
    Abstract [en]

    The amino acid-catalyzed aldol condensation is of great interest in organic synthesis and natural environments such as atmospheric particles. But kinetic and mechanistic information on these reactions is limited. In this work, the kinetics of the aldol condensation of acetaldehyde in water and aqueous salt solutions (NaCl, CaCl2, Na2SO4, MgSO4), catalyzed by five amino acids (glycine, alanine, serine, arginine, and proline) at room temperature (295 ± 2K) has been studied. Monitoring the formation of three products, crotonaldehyde, 2,4-hexadienal, and 2,4,6-octatrienal by UV-Visible absorption over 200 – 1100 nm revealed two distinct kinetic regimes: at low amino acid concentrations (in all cases, below 0.1 M) the overall reaction was first order with respect to acetaldehyde and kinetically limited by the formation of the enamine intermediate. At larger amino acid concentrations (at least 0.3 M) the kinetics was second order and controlled by the C-C bond-forming step. The first-order rate constants increased linearly with amino acid concentration, consistent with the enamine formation. Inorganic salts further accelerated the enamine formation according to their pKb plausibly by facilitating the iminium and/or enamine formation. The rate constant of the C-C bond-forming step varied with the square of amino acid concentration, suggesting the involvement of two amino acid molecules. Thus, the reaction proceeded via a Mannich pathway. However, the contribution of an aldol pathway, first-order in amino acid, could not be excluded. Our results show that the rate constant for the self-condensation of acetaldehyde in aqueous atmospheric aerosols (up to 10 of mM of amino acids) is identical as in sulfuric acid 10 - 15 M (kI ~ 10-7 - 10-6 s-1), clearly illustrating the potential importance of amino acid catalysis in natural environments. This work also demonstrates that under usual laboratory conditions and in natural environments aldol condensation is likely to be kinetically controlled by the enamine formation. Notably, kinetic investigations of the C-C bond-forming addition step would only be possible with high concentrations of amino acids.

  • 17. Ohlin, C. André
    et al.
    Dyson, Paul J.
    Laurenczy, Gábor
    Carbon monoxide solubility in ionic liquids: determination, prediction and relevance to hydroformylation2004In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 9, p. 1070-1071Article in journal (Refereed)
    Abstract [en]

    The solubility of carbon monoxide in 37 ionic liquids and in some organic solvents has been determined using high-pressure (13)C NMR spectroscopy; a method for predicting the CO solubility is demonstrated, and it was shown that the rate of the hydroformylation of 5-hexen-2-one does not correlate with the CO solubility, as expected from the determined relative solubility of CO compared to H(2).

  • 18. Ohlin, C André
    et al.
    Laurenczy, G
    Carbon dioxide reduction in biphasic aqueous-ionic liquid systems by pressurized hydrogen2003In: High Pressure Research, ISSN 0895-7959, E-ISSN 1477-2299, Vol. 23, no 3, p. 239-242Article in journal (Refereed)
    Abstract [en]

    This work reports the hydrogenation of carbon dioxide/inorganic carbonate salts to formic acid/formate in two phase systems comprising an ionic phase, in which the catalyst is immobilized, and an aqueous phase in which the carbonates and formate are confined, is reported. The reactions were followed in situ by multinuclear NMR. Pressurized H-2 gas was used for the reduction.

  • 19.
    Palma, Carlos-Andres
    et al.
    Technishe Universität München, Garching, Germany.
    Diller, Katharina
    Technishe Universität München, Garching, Germany.
    Berger, Reinhard
    Max-Planck-Institut für Polymerforschung, Mainz, Germany.
    Welle, Alexander
    Karlsruher Institut für Technologie, Eggenstein-Leopoldshafen, Germany.
    Björk, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Cabellos, Jose Luis Cabellos
    Universidad del País Vasco UPV/EHU, San Sebastián, Spain.
    Mowbray, Duncan John
    Universidad del País Vasco UPV/EHU, San Sebastián, Spain.
    Papageorgiou, Anthoula C.
    Technishe Universität München, Garching, Germany.
    Ivleva, Natalia P.
    Technische Universität München, München, Germany.
    Matich, Sonja
    Walter Schottky Institut, Garching, Germany.
    Margapoti, Emanuela
    Walter Schottky Institut, Garching, Germany.
    Niesser, Reinhard
    Technische Universität München, Germany.
    Menges, Bernhard
    Max-Planck-Institut für Polymerforschung, Mainz, Germany.
    Reichert, Joachim
    Technishe Universität München, Garching, Germany.
    Feng, Xinliang
    Max-Planck-Institut für Polymerforschung, Mainz, Germany.
    Räder, Hans Joachim
    Max-Planck-Institut für Polymerforschung, Mainz, Germany.
    Klappenberger, Florian
    Technishe Universität München, Garching, Germany.
    Rubio, Angel
    Universidad del País Vasco UPV/EHU, San Sebastián, Spain.
    Müllen, Klaus
    Max-Planck-Institut für Polymerforschung, Mainz, Germany.
    Barth, Johannes V.
    Technishe Universität München, Garching, Germany.
    Photo-induced C-C reactions on insulators towards photolithography of graphene nanoarchitectures2014In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, p. 4651-4658Article in journal (Refereed)
    Abstract [en]

    On-surface chemistry for atomically precise sp2 macromolecules requires top-down lithographic methods on insulating surfaces in order to pattern the long-range complex architectures needed by the semiconductor industry. Here, we fabricate sp2-carbon nm-thin films on insulators and under ultra-high vacuum (UHV) conditions from photo-coupled brominated precursors. We reveal that covalent coupling is initiated by C-Br bond cleavage through photon energies exceeding 4.4 eV, as monitored by laser desorption ionization (LDI) mass spectrometry (MS) and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) gives insight into the mechanisms of C-Br scission and C-C coupling processes. Further, unreacted material can be sublimed and the coupled sp2-carbon precursors can be graphitized by e-beam treatment at 500°C, demonstrating promising applications in photolithography of graphene nanoarchitectures. Our results present UV-induced reactions on insulators for the formation of all sp2-carbon architectures, thereby converging top-down lithography and bottom-up on-surface chemistry into technology.

  • 20.
    Parada, Giovanny A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Synthesis of Biomimetic Systems for Proton and Electron Transfer Reactions in the Ground and Excited State2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A detailed understanding of natural photosynthesis provides inspiration for the development of sustainable and renewable energy sources, i.e. a technology that is capable of converting solar energy directly into chemical fuels. This concept is called artificial photosynthesis. The work described in this thesis contains contributions to the development of artificial photosynthesis in two separate areas.

    The first one relates to light harvesting with a focus on the question of how electronic properties of photosensitizers can be tuned to allow for efficient photo-induced electron transfer processes. The study is based on a series of bis(tridentate)ruthenium(II) polypyridyl complexes, the geometric properties of which make them highly appealing for the construction of linear donor-photosensitizer-acceptor arrangements for efficient vectorial photo-induced electron transfer reactions. The chromophores possess remarkably long lived 3MLCT excited states and it is shown that their excited-state oxidation strength can be altered by variations of the ligand scaffold over a remarkably large range of 900 mV.

    The second area of relevance to natural and artificial photosynthesis that is discussed in this thesis relates to the coupled movement of protons and electrons. The delicate interplay between these two charged particles regulates thermodynamic and kinetic aspects in many key elementary steps of natural photosynthesis, and further studies are needed to fully understand this concept. The studies are based on redox active phenols with intramolecular hydrogen bonds to quinolines. The compounds thus bear a strong resemblance to the tyrosine/histidine couple in photosystem II, i.e. the water-plastoquinone oxidoreductase enzyme in photosynthesis. The design of the biomimetic models is such that the distance between the proton donor and acceptor is varied, enabling studies on the effect the proton transfer distance has on the rate of proton-coupled electron transfer reactions. The results of the studies have implications for the development of artificial photosynthesis, in particular in connection with redox leveling, charge accumulation, as well as electron and proton transfer.

    In addition to these two contributions, the excited-state dynamics of the intramolecular hydrogen-bonded phenols was investigated, thereby revealing design principles for technological applications based on excited-state intramolecular proton transfer and photoinduced tautomerization.

  • 21.
    Park, Sungkyu
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Division of Pharmacognosy.
    Cyclotides evolve: Studies on their natural distribution, structural diversity, and activity2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The cyclotides are a family of naturally occurring peptides characterized by cyclic cystine knot (CCK) structural motif, which comprises a cyclic head-to-tail backbone featuring six conserved cysteine residues that form three disulfide bonds. This unique structural motif makes cyclotides exceptionally resistant to chemical, thermal and enzymatic degradation. They also exhibit a wide range of biological activities including insecticidal, cytotoxic, anti-HIV and antimicrobial effects.

    The cyclotides found in plants exhibit considerable sequence and structural diversity, which can be linked to their evolutionary history and that of their host plants. To clarify the evolutionary link between sequence diversity and the distribution of individual cyclotides across the genus Viola, selected known cyclotides were classified using signature sequences within their precursor proteins. By mapping the classified sequences onto the phylogenetic system of Viola, we traced the flow of cyclotide genes over evolutionary history and were able to estimate the prevalence of cyclotides in this genus. In addition, the structural diversity of the cyclotides was related to specific features of the sequences of their precursor proteins, their evolutionary selection and expression levels.

    A number of studies have suggested that the biological activities of the cyclotides are due to their ability to interact with and disrupt biological membranes. To better explain this behavior, quantitative structure-activity relationship (QSAR) models were developed to link the cyclotides’ biological activities to the membrane-interactive physicochemical properties of their molecular surfaces. Both scalar quantities (such as molecular surface areas) and moments (such as the distributions of specific properties over the molecular surface) were systematically taken into account in the development of these models. This approach allows the physicochemical properties of cyclotides to be geometrically interpreted, facilitating the development of guidelines for drug design using cyclotide scaffolds.

    Finally, an optimized microwave-assisted Fmoc-SPSS procedure for the total synthesis of cyclotides was developed. Microwave irradiation is used to accelerate and improve all the key steps in cyclotide synthesis, including the assembly of the peptide backbone by Fmoc-SPPS, the cleavage of the protected peptide, and the introduction of a thioester at the C-terminal carboxylic acid to obtain the head-to-tail cyclized cyclotide backbone by native chemical ligation. 

  • 22.
    Pendrill, Robert
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sørensen, Ole W.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Suppressing one-bond homonuclear 13C,13C scalar couplings in the J-HMBC NMR experiment: application to 13C site-specifically labeled oligosaccharides2014In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 52, no 3, p. 82-86Article in journal (Refereed)
    Abstract [en]

    Site-specific C-13 isotope labeling is a useful approach that allows for the measurement of homonuclear C-13,C-13 coupling constants. For three site-specifically labeled oligosaccharides, it is demonstrated that using the J-HMBC experiment for measuring heteronuclear long-range coupling constants is problematical for the carbons adjacent to the spin label. By incorporating either a selective inversion pulse or a constant-time element in the pulse sequence, the interference from one-bond C-13,C-13 scalar couplings is suppressed, allowing the coupling constants of interest to be measured without complications. Experimental spectra are compared with spectra of a nonlabeled compound as well as with simulated spectra. The work extends the use of the J-HMBC experiments to site-specifically labeled molecules, thereby increasing the number of coupling constants that can be obtained from a single preparation of a molecule.

  • 23.
    Pu, Maoping
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Privalov, Timofei
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ab initio dynamics trajectory study of the heterolytic cleavage of H2 by a Lewis acid [B(C6F5)3] and a Lewis base [P(tBu)3]2013In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, no 15, article id 154305Article in journal (Refereed)
    Abstract [en]

    Activation of H-2 by a frustrated Lewis pair (FLP) composed of B(C6F5)(3) and P(tBu)(3) species has been explored with high level direct ab initio molecular dynamics (AIMD) simulations at finite temperature (T = 300 K) in gas phase. The initial geometrical conditions for the AIMD trajectory calculations, i.e., the near attack conformations of FLP + H-2, were devised using the host-guest model in which suitable FLP conformations were obtained from the dynamics of the B(C6F5)(3)/P(tBu)(3) pair in gas phase. AIMD trajectory calculations yielded microscopic insight into effects which originate from nuclear motion in the reacting complex, e. g., the alternating compression/elongation of the boron-phosphorous distance and the change of the pyramidality of boron in B(C6F5)(3). The ensemble averaged trajectory analysis has been compared with the minimum energy path (MEP) description of the reaction. Similar to MEP, AIMD shows that an attack of the acid/base pair on the H-H bond gives rise to the polarization of the H-2 molecule and as a consequence generates a large dipole moment of the reacting complex. The MEP and AIMD portrayals of the reaction are fundamentally different in terms of the magnitude of the motion of nuclei in B(C6F5)(3) and P(tBu)(3) during the H-2 cleavage. In the AIMD trajectory simulations, geometries of B(C6F5)(3) and P(tBu)(3) appear as nearly frozen on the short time scale of the H-2 cleavage. This is contrary to the MEP picture. Several of the concepts which arise from this work, e. g., separation of time scales of nuclear motion and the time-dependence of the donor-acceptor interactions in the reacting complex, are important for the understanding of chemical reactivity and catalysis.

  • 24.
    Ramstadius, Clinton
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Boklund, Mikael
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Cumpstey, Ian
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Conversion of fructose into a building block for the synthesis of carbocyclic mannose mimics2011In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 22, no 4, p. 399-405Article in journal (Refereed)
    Abstract [en]

    Fructose was converted into C-1 diastereomeric carbocyclic building blocks resembling mannose using ruthenium-catalysed ring-closing metathesis as a key step. The potential use of the compounds in the synthesis of valienamine pseudodisaccharides is demonstrated using Mitsunobu coupling chemistry directly between a carbohydrate sulfonamide and the carbasugar C-1 alcohols.

  • 25.
    Salinas, Borja Cirera
    et al.
    Technische Universität München, Garching, Germany.
    Zhang, Yi-Qi
    Technische Universität München, Garching, Germany.
    Björk, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Klyatskaya, Svetlana
    Karlsruhe Institute of Technology, Garching, Germany.
    Chen, Zhi
    Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany.
    Ruben, Mario
    Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany.
    Barth, Johannes V.
    Technische Universität München, Garching, Germany.
    Klappenberger, Florian
    Technische Universität München, Garching, Germany.
    Synthesis of Extended Graphdiyne Wires by Vicinal Surface Templating2014In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 14, no 4, p. 1891-1897Article in journal (Refereed)
    Abstract [en]

    Surface-assisted covalent synthesis currently evolves into an important approach for the fabrication of functional nanostructures at interfaces. Here, we employ scanning tunneling microscopy to investigate the homo-coupling reaction of linear, terminal alkyne-functionalized polyphenylene building-blocks on noble metal surfaces under ultra-high vacuum. On the flat Ag(111) surface thermal activation triggers a variety of side-reactions resulting in irregularly-branched polymeric networks. Upon alignment along the step-edges of the Ag(877) vicinal surface drastically improves the chemoselectivity of the linking process permitting the controlled synthesis of extended-graphdiyne wires with lengths reaching 30 nm. The ideal hydrocarbon scaffold is characterized by density functional theory as a 1D, direct band gap semiconductor material with both HOMO and LUMO-derived bands promisingly isolated within the electronic structure. The templating approach should be applicable to related organic precursors and different reaction schemes thus bears general promise for the engineering of novel low-dimensional carbon-based materials.

  • 26.
    Sun, Bing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Mindemark, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Morozov, Evgeny V.
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, Teknikringen 36, SE-10044 Stockholm, Sweden.
    Costa, Luciano T.
    Univ Fed Fluminense, Inst Quim, Dept Quim Fis, Outeiro Sao Joao Batista S-N, BR-24020150 Niteroi, RJ, Brazil.
    Bergman, Martin
    Chalmers, Dept Phys, SE-41296 Gothenburg, Sweden.
    Johansson, Patrik
    Chalmers, Dept Phys, SE-41296 Gothenburg, Sweden.
    Fang, Yuan
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, Teknikringen 36, SE-10044 Stockholm, Sweden.
    Furó, István
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, Teknikringen 36, SE-10044 Stockholm, Sweden.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ion transport in polycarbonate based solid polymer electrolytes: experimental and computational investigations2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 14, p. 9504-9513Article in journal (Refereed)
    Abstract [en]

    Among the alternative host materials for solid polymer electrolytes (SPEs), polycarbonates have recently shown promising functionality in all-solid-state lithium batteries from ambient to elevated temperatures. While the computational and experimental investigations of ion conduction in conventional polyethers have been extensive, the ion transport in polycarbonates has been much less studied. The present work investigates the ionic transport behavior in SPEs based on poly(trimethylene carbonate) (PTMC) and its co-polymer with epsilon-caprolactone (CL) via both experimental and computational approaches. FTIR spectra indicated a preferential local coordination between Li+ and ester carbonyl oxygen atoms in the P(TMC20CL80) co-polymer SPE. Diffusion NMR revealed that the co-polymer SPE also displays higher ion mobilities than PTMC. For both systems, locally oriented polymer domains, a few hundred nanometers in size and with limited connections between them, were inferred from the NMR spin relaxation and diffusion data. Potentiostatic polarization experiments revealed notably higher cationic transference numbers in the polycarbonate based SPEs as compared to conventional polyether based SPEs. In addition, MD simulations provided atomic-scale insight into the structure-dynamics properties, including confirmation of a preferential Li+-carbonyl oxygen atom coordination, with a preference in coordination to the ester based monomers. A coupling of the Li-ion dynamics to the polymer chain dynamics was indicated by both simulations and experiments.

  • 27.
    Swerin, Agne
    et al.
    YKI, Institute for Surface Chemistry, Sweden.
    Brandner, Birgitt
    Wallqvist, Vivica
    Wåhlander, Martin
    YKI, Institute for Surface Chemistry, Sweden.
    Probing molecular, nanoscale and adhesive forces related to fiber-fiber bonding and optimized surface interactions2009In: International Conference on Nanotechnology for the Forest Products Industry 2009, Edmonton Canada, 2009, Vol. 1, p. 229-283Conference paper (Refereed)
  • 28.
    Swerin, Agne
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Sundin, Mikael
    Wåhlander, Martin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Formulation of superhydrophobic pigment coatings2015In: Formulation of superhydrophobic pigment coatings, TAPPI Press, 2015, Vol. 2, p. 1410-1424Conference paper (Refereed)
  • 29.
    Säwén, Elin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stevensson, Baltzar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Östervall, Jennie
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Maliniak, Arnold
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Molecular conformations in the pentasaccharide LNF-1 derived from NMR spectroscopy and molecular dynamics simulations2011In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 115, no 21, p. 7109-7121Article in journal (Refereed)
    Abstract [en]

    The conformational dynamics of the human milk oligosaccharide lacto-N-fucopentaose (LNF-1), α-l-Fucp-(1 → 2)-β-d-Galp-(1 → 3)-β-d-GlcpNAc-(1 → 3)-β-d-Galp-(1 → 4)-d-Glcp, has been analyzed using NMR spectroscopy and molecular dynamics (MD) computer simulations. Employing the Hadamard 13C-excitation technique and the J-HMBC experiment, 1H,13C trans-glycosidic J coupling constants were obtained, and from one- and two-dimensional 1H,1H T-ROESY experiments, proton–proton cross-relaxation rates were determined in isotropic D2O solution. In the lyotropic liquid-crystalline medium consisting of ditetradecylphosphatidylcholine, dihexylphosphatidylcholine, N-cetyl-N,N,N-trimethylammonium bromide, and D2O, 1H, 1H and one-bond 1H, 13C residual dipolar couplings (RDCs), as well as relative sign information on homonuclear RDCs, were determined for the pentasaccharide. Molecular dynamics simulations with explicit water were carried out from which the internal isomerization relaxation time constant, τN, was calculated for transitions at the ψ torsion angle of the β-(1 → 3) linkage to the lactosyl group in LNF-1. Compared to the global reorientation time, τM, of 0.6 ns determined experimentally in D2O solution, the time constant for the isomerization relaxation process, τN(scaled), is about one-third as large. The NMR parameters derived from the isotropic solution show very good agreement with those calculated from the MD simulations. The only notable difference occurs at the reducing end, which should be more flexible than observed by the molecular simulation, a conclusion in complete agreement with previous 13C NMR relaxation data. A hydrogen-bond analysis of the MD simulation revealed that inter-residue hydrogen bonds on the order of 30% were present across the glycosidic linkages to sugar ring oxygens. This finding highlights that intramolecular hydrogen bonds might be important in preserving well-defined structures in otherwise flexible molecules. An analysis including generalized order parameters obtained from nuclear spin relaxation experiments was performed and successfully shown to limit the conformational space accessible to the molecule when the number of experimental data are too scarce for a complete conformational analysis.

  • 30.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fulleranes by direct reaction with hydrogen gas at elevated conditions2010In: Fulleranes: the hydrogenated fullerenes / [ed] Franco Cataldo, Susana Iglesias-Groth, Dordrecht: Springer Netherlands, 2010, p. 85-103Chapter in book (Other academic)
    Abstract [en]

    Reaction of solid fullerenes with hydrogen gas occurs with or without catalysts at elevated conditions. Composition of hydrofullerene mixture obtained in this reaction depends strongly on temperature (350–450°C), hydrogen pressure (typically 10–120 bar) and duration of treatment. Saturation of hydrogenation occurs after tens of hours, depending on temperature of reaction. In case of extra strong hydrogenation prolonged reaction leads to formation of fulleranes with composition C60Hx approaching number of hydrogen atoms X = 60. These fulleranes are highly unstable and decompose first with formation of fragmented hydrofullerenes with progressively smaller number of carbon atoms C59, C58, C57 etc., followed by collapse of cage structure. Since the collapse occurs at the conditions of high temperature and high hydrogen pressure, all breaking C–C bonds are saturated immediately with hydrogen and new C–H bonds are formed. Therefore, large fragments of fullerane molecules are able to survive and large polycyclic aromatic hydrocarbons (PAH’s) formed as a result of cage structure collapse.

  • 31. Vidis, Ana
    et al.
    Ohlin, C. André
    Laurenczy, Gábor
    Küsters, Ernst
    Sedelmeier, Gottfried
    Dyson, Paul J.
    Rationalisation of solvent effects in the diels-alder reaction between cyclopentadiene and methyl acrylate in room temperature ionic liquids2005In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 347, no 2-3, p. 266-274Article in journal (Refereed)
    Abstract [en]

    The Diels-Alder reaction between cyclopentadiene and methyl acrylate in ionic liquids has been studied in detail. The effect of contamination of the ionic liquids by common impurities, viz. sodium and chloride ions, and water, on the selectivity has been investigated. The presence of high concentrations of chloride was found to decrease the selectivity. Anion and, in particular, cation effects have been investigated using an extensive series of air-stable room temperature ionic liquids, and kinetic parameters have been determined. It has been found that strongly interacting groups, particularly electrophilic moieties on the cation, accelerate the formation of the endo products. Substrate solubility intimately connected to the selectivity was found to be mainly anion dependent. An NMR-based solvent parameter scale and semi-empirical models are used to analyse the results and provide a tool for the prediction of selectivities in ionic liquids.

  • 32.
    Wallin, Staffan
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Department of Physical and Analytical Chemistry, Physical Chemistry I. Physics, Department of Physics and Materials Science, Chemical Physics.
    Davidsson, Jan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Department of Physical and Analytical Chemistry, Physical Chemistry I. Physics, Department of Physics and Materials Science, Chemical Physics.
    Modin, Judit
    Department of Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Department of Physical and Analytical Chemistry, Physical Chemistry I. Physics, Department of Physics and Materials Science, Chemical Physics. Organisk kemi.
    Hammarström, Leif
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Department of Physical and Analytical Chemistry, Physical Chemistry I. Physics, Department of Physics and Materials Science, Chemical Physics.
    Femtosecond Transient Absorption Anisotropy Study on [Ru(bpy)3]2+ and [Ru(bpy)(py)4]2+. Ultrafast Interligand Randomization of the MLCT State2005In: J. Phys. Chem. A, no 109, p. 4697-4704Article in journal (Refereed)
    Abstract [en]

    It is known that the relaxed excited state of [Ru(bpy)3]2+ is best described as a metal to ligand charge transfer (MLCT) state having one formally reduced bipyridine and two neutral. Previous reports have suggested [Malone, R. et al. J.Chem. Phys 1991, 95, 8970] that the electron "hops" from ligand to ligand in the MLCT state with a time constant of about 50 ps in acetonitrile. However, we have done transient absorption anisotropy measurements indicating that already after one picosecond the molecule has no memory of which bipyridine was initially photoselected, which suggest an ultrafast interligand randomization of the MLCT state.

  • 33.
    Wang, Lei
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Artificial Photosynthesis: Molecular Catalysts for Water Oxidation2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Artificial photosynthesis provides a promising solution to the future sustainable energy system. Water is the only suitably sufficient protons and electrons supplier by the reaction of water oxidation. However, this reaction is both kinetically and thermodynamically demanding, leading to a sluggish kinetics unless the introduction of a catalyst.The theme of this thesis is to design, synthesize and evaluate molecular catalysts for water oxidation. This thesis consists of seven parts:The first chapter presents a general introduction to the field of homogenous catalysis of water oxidation, including catalysts design, examination and mechanistic investigation.The second chapter investigates the electronic and noncovalent-interaction effects of the ligands on the activities of the catalysts.In the third chapter, halogen substitutes are introduced into the axial ligands of the ruthenium catalysts. It is proved that the hydrophobic effect of the halogen atom dramatically enhanced the reactivity of the catalysts.Chapter four explores a novel group of ruthenium catalysts with imidazole-DMSO pair of axial ligands, in which the DMSO is proved to be crucial for the high efficiency of the catalysts.Chapter five describes the light-driven water oxidation including the three-component system and the sensitizer-catalyst assembled system. It is found that the common Ru(bpy)32+ dye can act as an electron relay and further benefit the electron transfer as well as the photo-stability of the system.In chapter six, aiming to the future application, selected ruthenium catalysts have been successfully immobilized on electrodes surfaces, and the electrochemical water oxidation is achieved with high efficiency.Finally, in the last chapter, a novel molecular catalyst based on the earth abundant metal ―nickel has been designed and synthesized. The activities as well as the mechanism have been explored.

  • 34.
    Yang, Huaiyu
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Rasmuson, Åke
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. Limerick University.
    Nucleation of butyl paraben in different solvents2013In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 13, no 10, p. 4226-4238Article in journal (Refereed)
    Abstract [en]

    The primary nucleation induction time of butyl paraben in pure solvents: acetone, ethyl acetate, methanol, ethanol, and propanol and in 70% and 90% ethanol aqueous mixtures has been determined. At each condition, about 100 experiments have been performed in 5 mL scale to capture the statistics of the nucleation process. The induction times at each condition show a wide variation. The data has been evaluated within the framework of the classical nucleation theory using several of the current approaches. Overall, the data obtained from the different methods of evaluation are surprisingly consistent. At comparable driving forces, nucleation is clearly fastest in acetone and slowest in propanol, with methanol, ethyl acetate, and ethanol in between. Adding water to the ethanol leads to a clear reduction in the nucleation rate. The solid-solution interfacial energy of butyl paraben in the different solvents decreases in the order: 70% ethanol > 90% ethanol > propanol > ethanol > ethyl acetate > methanol > acetone, which is surprisingly well-correlated to a decreasing solvent boiling point. It is shown that the same trend can be found for other systems in the literature. With the assumption that the stronger the bonding in the bulk phases, the higher the interfacial energy becomes, this observation is paralleled by the fact that a metastable polymorph has a lower interfacial energy than the stable form and that a solid compound with a higher melting point appears to have a higher solid-melt and solid-solution interfacial energy.

  • 35.
    Yang, Huaiyu
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Rasmuson, Åke
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. Limerick University.
    Ternary diagrams of ethyl paraben and propyl parabenManuscript (preprint) (Other academic)
  • 36.
    Yang, Huaiyu
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. Strathclyde Institute of Pharmacy and Pharmaceutical Sciences, University of Strathclyde3, United Kingdom .
    Svärd, Michael
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. Department of Chemical and Environmental Science, Materials and Surface Science Institute, University of Limerick, Ireland .
    Zeglinski, Jacek
    Rasmuson, Åke
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. Department of Chemical and Environmental Science, Materials and Surface Science Institute, University of Limerick, Ireland .
    Influence of Solvent and Solid-State Structure on Nucleation of Parabens2014In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 14, no 8, p. 3890-3902Article in journal (Refereed)
    Abstract [en]

    In the present work, the induction time for nucleation of ethyl paraben (EP) and propyl paraben (PP) in ethanol, ethyl acetate, and acetone has been measured at different levels of supersaturation. The induction time shows a wide variation among repeat experiments, indicative of the stochastic nature of nucleation. The solid-liquid interfacial energy and the size of the critical nucleus have been determined according to the classical nucleation theory. Combined with previous results for butyl paraben (BP), the nucleation behavior is analyzed with respect to differences in the solid phase of the three pure compounds, and with respect to differences in the solution. The results indicate that the difficulty of nucleation in ethanol and acetone increases in the order BP < PP < EP but is approximately the same in ethyl acetate. For each of the three parabens, the difficulty of nucleation increases in the order acetone < ethyl acetate < ethanol. The Gibbs energy of melting increases in the order BP < PP < EP, but the crystal structures are quite similar resulting in the basic crystal shape being very much the same. The solid-liquid interfacial energy is reasonably well correlated to the solvation energy, and even better correlated to the deformation energy, of the solute molecule within the first solvation shell as obtained by density functional theory calculations.

1 - 36 of 36
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