Viser treff 408-427 av 527

    • Relativistic effects on the NMR parameters of Si, Ge, Sn, and Pb alkynyl compounds: Scalar versus spin-orbit effects 

      Demissie, Taye Beyene (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-01)
      The NMR chemical shifts and indirect spin-spin coupling constants of 12 molecules containing <sup>29</sup>Si, <sup>73</sup>Ge, <sup>119</sup>Sn, and <sup>207</sup>Pb [X(CCMe)<sub>4</sub>, Me<sub>2</sub>X(CCMe)<sub>2</sub>, and Me<sub>3</sub>XCCH] are presented. The results are obtained from non-relativistic as well as two- and four-component relativistic density functional theory (DFT) calculations. ...
    • Relativistic four-component calculations of Buckingham birefringence using London atomic orbitals 

      Bast, Radovan; Ruud, Kenneth; Rizzo, Antonio; Helgaker, Trygve (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      We present the first relativistic study of the electric-field-gradient induced birefringence (Buckingham birefringence), with application to the series of molecules CX2 (X = O, S, Se, Te). A recently developed atomic-orbital-driven scheme for the calculation of time-dependent molecular properties using one-, two- and four-component relativistic wave functions (Bast et al. in Chem Phys 356:177, 2009) ...
    • Relativistic four-component calculations of indirect nuclear spin-spin couplings with efficient evaluation of the exchange-correlation response kernel 

      Kristkova, Anezka; Komorovsky, Stanislav; Repisky, Michal; Malkin, Vladimir G.; Malkina, Olga L. (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-03-16)
      In this work, we report on the development and implementation of a new scheme for efficient calculation of indirect nuclear spin-spin couplings in the framework of four-component matrix Dirac-Kohn-Sham approach termed matrix Dirac-Kohn-Sham restricted magnetic balance resolution of identity for J and K, which takes advantage of the previous restricted magnetic balance formalism and the density ...
    • Relativistic Four-Component DFT Calculations of Vibrational Frequencies 

      Jakubowska, Katarzyna; Pecul-Kudelska, Magdalena; Ruud, Kenneth (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-29)
      We investigate the effect of relativity on harmonic vibrational frequencies. Density functional theory (DFT) calculations using the four-component Dirac–Coulomb Hamiltonian have been performed for 15 hydrides (H<sub>2</sub>X, X = O, S, Se, Te, Po; XH<sub>3</sub>, X = N, P, As, Sb, Bi; and XH<sub>4</sub>, X = C, Si, Ge, Sn, Pb) as well as for HC≡CPbH<sub>3</sub>. The vibrational frequencies have been ...
    • Relativistic four-component linear damped response TDDFT for electronic absorption and circular dichroism calculations 

      Konecny, Lukas; Repisky, Michal; Ruud, Kenneth; Komorovsky, Stanislav (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-21)
      We present a detailed theory, implementation, and a benchmark study of a linear damped response time-dependent density functional theory (TDDFT) based on the relativistic four-component (4c) Dirac–Kohn–Sham formalism using the restricted kinetic balance condition for the small-component basis and a noncollinear exchange–correlation kernel. The damped response equations are solved by means of a ...
    • Relativity as a Synthesis Design Principle: A Comparative Study of [3 + 2] Cycloaddition of Technetium(VII) and Rhenium(VII) Trioxo Complexes with Olefins 

      Braband, Henrik; Benz, Michael; Spingler, Bernhard; Conradie, Jeanet; Roger, Alberto; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-13)
      The difference in [3 + 2] cycloaddition reactivity between fac- [MO<sub>3</sub>(tacn)]<sup>+</sup> (M = Re, <sup>99</sup>Tc; tacn = 1,4,7-triazacyclononane) complexes has been reexamined with a selection of unsaturated substrates including sodium 4- vinylbenzenesulfonate, norbornene, 2-butyne, and 2-methyl-3-butyn-2-ol (2MByOH). None of the substrates was found to react with the Re cation in water ...
    • Renewable Solvents for Palladium-Catalyzed Carbonylation Reactions 

      Ismael, Aya; Gevorgyan, Ashot; Skrydstrup, Troels; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-04)
      Solvents constitute the largest component for many chemical processes and substitution of nonrenewable solvents is a longstanding goal for green chemistry. Here, we show that Pd-catalyzed carbonylative couplings, such as carbonylative cross-couplings, aminocarbonylations, and alkoxycarbonylations, can be successfully realized using renewable solvents. The present research covers not only well-established ...
    • Resolution-of-identity accelerated relativistic two- and four-component electron dynamics approach to chiroptical spectroscopies 

      Konecny, Lukas; Kadek, Marius; Komorovsky, Stanislav; Ruud, Kenneth; Repisky, Michal (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-27)
      We present an implementation and application of electron dynamics based on real-time time-dependent density functional theory (RT-TDDFT) and relativistic 2-component X2C and 4-component Dirac–Coulomb (4c) Hamiltonians to the calculation of electron circular dichroism and optical rotatory dispersion spectra. In addition, the resolution-of-identity approximation for the Coulomb term (RI-J) is introduced ...
    • 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 ...
    • Response properties of embedded molecules through the polarizable embedding model 

      Steinmann, Casper; Reinholdt, Peter; Nørby, Morten Steen; Kongsted, Jacob; Olsen, Jógvan Magnus Haugaard (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-04)
      The polarizable embedding (PE) model is a fragment‐based quantum‐classical approach aimed at accurate inclusion of environment effects in quantum‐mechanical response property calculations. The aim of this tutorial review is to give insight into the practical use of the PE model. Starting from a set of molecular structures and until you arrive at the final property, there are many crucial details to ...
    • Review of DFT-simulated and experimental electrochemistry properties of the polypyridyl Row-1 Mn, Fe & Co, and Group-8 Fe, Ru and Os MLCT complexes 

      Von Eschwege, Karel G.; Conradie, Jeanet (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-30)
      Ruthenium had up to date been pivotal in electro- and photocatalytic applications involving reduction of CO<sub>2</sub> and H<sub>2</sub>O, and dye-sensitized solar cells. Commercial applications would seek use of earth-abundant metals instead. Towards this goal, it is key to review the synthesis, electrochemical and spectroscopical properties of associated metal-to-ligand charge transfer complexes ...
    • Rhenium Biscorrole Sandwich Compounds: XAS Evidence for a New Coordination Motif 

      Alemayehu, Abraham; Abernathy, Macon Jedediah; Conradie, Jeanet; Sarangi, Ritimukta; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-23)
      The interaction of three free-base meso-tris(p-X-phenyl)corroles H3[TpXPC] (X = H, CH3, OCH3) with Re2(CO)10 at 235 °C in the presence of K2CO3 in o-dichlorobenzene has led to putative rhenium biscorrole sandwich compounds with the formula ReH[TpXPC]2. Density functional theory calculations and Re L3-edge extended X-ray absorption fine structure measurements suggest a seven-coordinate metal center, ...
    • Rhenium Corrole Dimers: Electrochemical Insights into the Nature of the Metal–Metal Quadruple Bond 

      Alemayehu, Abraham; Mccormick-Mcpherson, Laura J; Conradie, Jeanet; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-17)
      The interaction of free-base triarylcorroles with Re<sub>2</sub>(CO)<sub>10</sub> in 1,2- dichlorobenzene in the presence of 2,6-lutidine at 180 °C under strict anerobic conditions afforded approximately 10% yields of rhenium corrole dimers. The compounds exhibited diamagnetic <sup>1</sup> H NMR spectra consistent with a metal−metal quadruple bond with a σ<sup>2</sup> π<sup>4</sup> δ<sup>2</sup> ...
    • Rhenium-Imido Corroles 

      Alemayehu, Abraham; Teat, Simon J.; Borisov, Sergey M.; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-04-10)
      Metallocorroles involving 5d transition metals are currently of interest as near-IR phosphors and as photosensitizers for oxygen sensing and photodynamic therapy. Their syntheses, however, are often bedeviled by capricious and low-yielding protocols. Against this backdrop, we describe rhenium-imido corroles, a new class of 5d metallocorroles, synthesized simply and in respectable (∼30%) yields via ...
    • Rhodium-Catalyzed Hydrocarboxylation: Mechanistic Analysis Reveals Unusual Transition State for Carbon–Carbon Bond Formation 

      Pavlovic, Ljiljana; Vaitla, Janakiram; Bayer, Annette; Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-12)
      The mechanism of rhodium-COD-catalyzed hydrocarboxylation of styrene derivatives and α,β-unsaturated carbonyl compounds with CO<sub>2</sub> has been investigated using density functional theory (PBE-D2/IEFPCM). The calculations support a catalytic cycle as originally proposed by Mikami and co-workers including β-hydride elimination, insertion of the unsaturated substrate into a rhodium–hydride bond, ...
    • Rhodium-Catalyzed Synthesis of Sulfur Ylides via in Situ Generated Iodonium Ylides 

      Vaitla, Janakiram; Hopmann, Kathrin H.; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-22)
      A convenient strategy for the synthesis of sulfur ylides via rhodium-catalyzed coupling of in situ generated iodonium ylides with sulfides or sulfoxides has been developed. A wide range of sulfur ylides were obtained in moderate to good yields from inexpensive sulfur compounds and active methylene compounds with a short reaction time (MW, 5–10 min) or 12–16 h at rt. Furthermore, these sulfoxonium ...
    • Role of conical intersection seam topography in the chemiexcitation of 1,2-dioxetanes 

      Fdez. Galván, Ignacio; Brakestad, Anders; Vacher, Morgane (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-06)
      Chemiexcitation, the generation of electronic excited states by a thermal reaction initiated on the ground state, is an essential step in chemiluminescence, and it is mediated by the presence of a conical intersection that allows a nonadiabatic transition from ground state to excited state. Conical intersections classified as sloped favor chemiexcitation over ground state relaxation. The chemiexcitation ...
    • Role of zero-point vibrational corrections to carbon hyperfine coupling constants in organic pi radicals 

      Chen, Xiao; Rinkevicius, Zilvinas; Ruud, Kenneth; Ågren, Hans (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      By analyzing a set of organic π radicals, we demonstrate that zero-point vibrational corrections give significant contributions to carbon hyperfine coupling constants, in one case even inducing a sign reversal for the coupling constant. We discuss the implications of these findings for the computational analysis of electron paramagnetic spectra based on hyperfine coupling constants evaluated at the ...
    • Room Temperature-Stable Magnesium Electride via Ni(II) Reduction 

      Do, Cuong Dat; Day, Craig S.; Odena, Carlota; Benet-Buchholz, Jordi; Xu, Liang; Foroutan-Nejad, Cina; Hopmann, Kathrin Helen; Martin, Ruben (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-13)
      Herein, we report the synthesis of highly reduced bipyridyl magnesium complexes and the first example of a stable organic magnesium electride supported by quantum mechanical computations and X-ray diffraction. These complexes serve as unconventional homogeneous reductants due to their high solubility, modular redox potentials, and formation of insoluble, non-coordinating byproducts. The applicability ...
    • Rotational averaging of multiphoton absorption cross sections 

      Friese, Daniel Henrik; Beerepoot, Maarten T. P.; Ruud, Kenneth (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)