Viser treff 241-260 av 527

    • Exploration of New Biomass-Derived Solvents: Application to Carboxylation Reactions 

      Gevorgyan, Ashot; Hopmann, Kathrin Helen; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-07)
      A range of hitherto unexplored biomass‐derived chemicals have been evaluated as new sustainable solvents for a large variety of CO<sub>2</sub>‐based carboxylation reactions. Known biomass‐derived solvents (biosolvents) are also included in the study and the results are compared with commonly used solvents for the reactions. Biosolvents can be efficiently applied in a variety of carboxylation reactions, ...
    • Formal C-H carboxylation of unactivated arenes with carbon dioxide 

      Gevorgyan, Ashot; Hopmann, Kathrin Helen; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-31)
      A formal C−H carboxylation of unactivated arenes using CO<sub>2</sub> in green solvents is described. The present strategy combines a sterically controlled Ir‐catalyzed C−H borylation followed by a Cu‐catalyzed carboxylation of the in situ generated organoboronates. The reaction is highly regioselective for the C−H carboxylation of 1,3‐disubstituted and 1,2,3‐trisubstituted benzenes, 1,2‐ or ...
    • Two-photon absorption in host-guest complexes 

      Alam, Mehboob; Ruud, Kenneth (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-17)
      We present an extensive analysis of one- and two-photon absorption processes in some organic host-guest (H-G) complexes using linear and quadratic response theory within the framework of time-dependent density functional theory. For this purpose, we have considered all possible 20 host-guest complexes constructed from 4 host and 5 guest molecules. We have analysed how the one- and two-photon activity ...
    • Dalton Project: A Python platform for molecular- and electronic-structure simulations of complex systems 

      Olsen, Jógvan Magnus Haugaard; Reine, Simen Sommerfelt; Vahtras, Olav; Kjellgren, Erik; Reinholdt, Peter; Dundas, Karen O.H; Li, Xin; Cukras, Janusz; Ringholm, Magnus; Hedegård, Erik Donovan; Di Remigio, Roberto; List, Nanna H.; Faber, Rasmus; Tenorio, Bruno Nunes Cabral; Bast, Radovan; Pedersen, Thomas Bondo; Rinkevicius, Zilvinas; Sauer, Stephan P. A.; Mikkelsen, Kurt V.; Kongsted, Jacob; Coriani, Sonia; Ruud, Kenneth; Helgaker, Trygve; Jensen, Hans Jørgen Aa.; Norman, Patrick (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-05)
      The <i>Dalton Project</i> provides a uniform platform access to the underlying full-fledged quantum chemistry codes Dalton and LSDalton as well as the PyFraME package for automatized fragmentation and parameterization of complex molecular environments. The platform is written in Python and defines a means for library communication and interaction. Intermediate data such as integrals are exposed to ...
    • The escherichia coli alkA gene is activated to alleviate mutagenesis by an oxidized deoxynucleoside 

      Grøsvik, Kristin; Tesfahun, Almaz Nigatu; Muruzábal-Lecumberri, Izaskun; Haugland, Gyri Teien; Leiros, Ingar; Ruoff, Peter; Kvaløy, Jan Terje; Knævelsrud, Ingeborg; Ånensen, Hilde; Alexeeva, Marina; Sato, Kousuke; Matsuda, Akira; Alseth, Ingrun; Klungland, Arne; Bjelland, Svein (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-25)
      The cellular methyl donor S-adenosylmethionine (SAM) and other endo/exogenous agents methylate DNA bases non-enzymatically into products interfering with replication and transcription. An important product is 3-methyladenine (m<sup>3</sup>A), which in <i>Escherichia coli</i> is removed by m<sup>3</sup>A-DNA glycosylase I (Tag) and II (AlkA). The <i>tag</i> gene is constitutively expressed, while ...
    • Rational selection of co-catalysts for the deaminative hydrogenation of amides 

      Artús Suàrez, Lluís; Jayarathne, Upul; Balcells, David; Bernskoetter, Wesley H.; Hazari, Nilay; Jaraiz, Martin; Nova, Ainara (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-20)
      The catalytic hydrogenation of amides is an atom economical method to synthesize amines. Previously, it was serendipitously discovered that the combination of a secondary amide co-catalyst with (<sup>iPr</sup>PNP)Fe(H)(CO) (<sup>iPr</sup>PNP = N[CH<sub>2</sub>CH<sub>2</sub>(P<sup>i</sup>Pr<sub>2</sub>)]<sub>2</sub>−), results in a highly active base metal system for deaminative amide hydrogenation. ...
    • Amphiphilic Rhenium-Oxo Corroles as a New Class of Sensitizers for Photodynamic Therapy 

      Einrem, Rune F.; Alemayehu, Abraham; Borisov, Sergey M.; Ghosh, Abhik; Gederaas, Odrun Arna (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-04-27)
      A set of rhenium(V)-oxo <i>meso</i>-triarylcorroles bearing ester and carboxylic acid functionalities were synthesized with a view to determining their potential for photodynamic therapy. Toward this end, we measured their near-IR phosphorescence and their ability to sensitize singlet oxygen formation. The two esters studied, Re<sup>V</sup>O 5,10,15-tris(<i>meta</i>-carbomethoxyphenyl)corrole and ...
    • ReSpect: Relativistic spectroscopy DFT program package 

      Repisky, Michal; Komorovsky, Stanislav; Kadek, Marius; Konecny, Lukas; Ekström, Ulf; Malkin, Elena; Kaupp, Martin; Ruud, Kenneth; Malkina, Olga L.; Malkin, Vladimir G. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-11)
      With the increasing interest in compounds containing heavier elements, the experimental and theoretical community requires computationally efficient approaches capable of simultaneous non-perturbative treatment of relativistic, spin-polarization, and electron correlation effects. The ReSpect program has been designed with this goal in mind and developed to perform relativistic density functional ...
    • Vinyl Sulfoxonium Ylide: A New Vinyl Carbenoid Transfer Reagent for the Synthesis of Heterocycles 

      Vaitla, Janakiram; Bayer, Annette; Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-10)
      Sulfoxonium ylides have recently gained prominence as safe carbenoid precursors in metal-catalyzed reactions. The stability and reactivity of sulfoxonium ylides depend on the substitution of the ylide carbon. The reactivity of vinyl-substituted sulfoxonium ylides is different and offers several advantages over known stabilized sulfoxonium ylides in the case of carbenoid transfer reactions. Herein, ...
    • Computational Investigation on the Photophysical Properties of Halogenated Tetraphenyl BODIPY 

      Pomogaev, Vladimir; Chiodo, Sandro; Ruud, Kenneth; Kuznetsova, Rimma; Avramov, Pavel V (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-07)
      The electronic structure, transition probabilities, and corresponding quantum yields of fluorescence in a family of dihalogen-tetraphenyl-aza-BODIPY were calculated at the Time-Dependent Density Functional and post-Hartree–Fock levels of theory. Excellent agreement between theoretical and experimental spectral-luminescent data was achieved with the HSE06 functional and the 6-311G* basis set. Because ...
    • Carbonylative Suzuki-Miyaura couplings of sterically hindered aryl halides: Synthesis of 2-aroylbenzoate derivatives 

      Ismael, Aya; Skrydstrup, Troels; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-10)
      We have developed a carbonylative approach to the synthesis of diversely substituted 2-aroylbenzoate esters featuring a new protocol for the carbonylative coupling of aryl bromides with boronic acids and a new strategy to favour carbonylative over non-carbonylative reactions. Two different synthetic pathways – (i) the alkoxycarbonylation of 2-bromo benzophenones and (ii) the carbonylative Suzuki–Miyaura ...
    • How To Make Your Computational Paper Interesting and Have It Published 

      Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-11)
      In 1987, the late German chemist Peter Hofmann of the University of Heidelberg wrote: “We still have a long way to go until a computation will be able to compete with or to substitute a lab experiment... one could then conclude that theoretical work in this field—not being quantitatively reliable anyhow—is rather useless, except for the purpose of keeping theorists busy.” However, Hofmann continued: ...
    • Main-Group-Element Isophlorin Complexes Revisited: The Question of a Subvalent Central Atom 

      Conradie, Jeanet; Brothers, Penelope Jane; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-15)
      A careful density functional theory reexamination of the geometric and electronic structures of reduced main-group porphyrin complexes E(Por)L2 (E = Si or Ge; L = pyridine or tetrahydrofuran), B2(Por), and C2(Por) has confirmed these as pure isophlorin derivatives with normal-valent coordinated central atoms. Only axially unligated Ge(Por) and the dications [B2(Por)]2+ and [C2(Por)]2+ feature aromatic ...
    • Relativistic Effects on a Metal-Metal Bond: Osmium Corrole Dimers 

      Alemayehu, Abraham; McCormick, Laura J; Vazquez Lima, Hugo; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-07)
      A series of metal–metal bonded osmium corrole dimers, {Os[TpXPC]}2, were synthesized in reasonably good yields (35–46%) via the interaction of the corresponding free-base meso-tris(p-X-phenyl)corroles (H3[TpXPC], X = CF3, H, CH3, and OCH3), Os3(CO)12, and potassium carbonate in 1,2,4-trichlorobenzene under an inert atmosphere at 180 °C over several hours. The complexes are only the second class of ...
    • Sulfoxonium Ylide Derived Metal Carbenoids in Organic Synthesis 

      Vaitla, Janakiram; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-12)
      As pioneered by Corey and Chaykovsky, sulfoxonium ylides have had widespread application in organic synthesis for more than a half century. In most of the reactions, sulfoxonium ylides were used to react with electrophiles. Under suitable reaction conditions these ylides can generate metal carbenoids and react with nucleophiles. By combining the typical reactivity of sulfoxonium ylides with ...
    • To Bind or Not to Bind: Mechanistic Insights into C–CO2 Bond Formation with Late Transition Metals 

      García-López, Diego; Pavlovic, Ljiljana; Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-04-03)
      In transition metal-mediated carboxylation reactions, CO<sub>2</sub> inserts into a metal–nucleophile bond. At the carboxylation transition state (TS), CO<sub>2</sub> may interact with the metal (<i>inner</i>-sphere path) or may insert without being activated by the metal (<i>outer</i>-sphere path). Currently, there is no consensus as to which path prevails. In order to establish general predictions ...
    • Stereochemistry of Transition-Metal Dinitrosyl Complexes. A Molecular Orbital Rationale for the Attracto and Repulso Conformations 

      Ghosh, Abhik; Conradie, Jeanet (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-25)
      Transition-metal dinitrosyl complexes constitute a fairly large class of compounds, exemplified by some 500 structures in the Cambridge Structural Database. While many of the complexes exhibit a claw-like cis-attracto conformation, a handful of them exhibit a peculiar repulso conformation, in which the two NO groups are splayed outward and away from each other. Surprisingly, no computational study ...
    • X-ray Absorption Spectroscopy as a Probe of Ligand Noninnocence in Metallocorroles: The Case of Copper Corroles 

      Lim, Hyeongtaek; Kolle, Ekaney Thomas; Hedman, Britt; Hodgson, Keith O; Ghosh, Abhik; Solomon, Edward I. (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-02)
      The question of ligand noninnocence in Cu corroles has long been a topic of discussion. Presented herein is a Cu K-edge X-ray absorption spectroscopy (XAS) study, which provides a direct probe of the metal oxidation state, of three Cu corroles, Cu[TPC], Cu[Br8TPC], and Cu[(CF3)8TPC] (TPC = meso-triphenylcorrole), and the analogous Cu(II) porphyrins, Cu[TPP], Cu[Br8TPP], and Cu[(CF3)8TPP] (TPP = ...
    • Temperature adaptation of DNA ligases from psychrophilic organisms 

      Berg, Kristel; Leiros, Ingar; Williamson, Adele Kim (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-02)
      DNA ligases operating at low temperatures have potential advantages for use in biotechnological applications. For this reason, we have characterized the temperature optima and thermal stabilities of three minimal Lig E-type ATP-dependent DNA ligase originating from Gram-negative obligate psychrophilic bacteria. The three ligases, denoted Vib-Lig, Psy-Lig, and Par-Lig, show a remarkable range of ...
    • QresFEP: An Automated Protocol for Free Energy Calculations of Protein Mutations in Q 

      Jespers, Willem; Isaksen, Geir Villy; Andberg, Tor Arne Heim; Vasile, Silvana; van Veen, Amber; Åqvist, Johan; Brandsdal, Bjørn Olav; Gutiérrez-de-Terán, Hugo (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-22)
      Predicting the effect of single-point mutations on protein stability or protein−ligand binding is a major challenge in computational biology. Free energy calculations constitute the most rigorous approach to this problem, though the estimation of converged values for amino acid mutations remains challenging. To overcome this limitation, we developed tailored protocols to calculate free energy ...