Walter Thiel

Max Planck Institute for Coal Research, Mülheim-on-Ruhr, North Rhine-Westphalia, Germany

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Publications (461)1652.19 Total impact

  • Bora Karasulu, Walter Thiel
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    ABSTRACT: The photophysical properties of a push-pull flavin derivative, roseoflavin (RoF), are investigated in different surroundings at the molecular level, with focus on intra-molecular charge transfer (ICT). Time-dependent density functional theory (TD-DFT, CAM-B3LYP functional) and DFT-based multi-reference configuration interaction (DFT/MRCI) are used to compute excited-state energies and one-electron properties of a truncated RoF model, roseolumiflavin (RoLF). Solvent effects are taken into account implicitly by the conductor-like polarizable continuum model and explicitly through a micro-solvation scheme. In the gas phase, the calculations predict no crossing between the lowest locally-excited (LE) and charge-transfer (CT) states upon twisting the dimethylamine donor group relative to the plane of the isoalloxazine acceptor moiety, whereas this crossing is found to be facile in solution (i.e., in water or benzene). Crossing of the LE and CT states facilitates ICT, which is the main cause of the fluorescence quenching and dual fluorescence character experimentally observed for roseoflavin in solution. The barrier for the ICT process is computed to be lower in water than in benzene, consistent with the enhanced ICT rates observed in more polar solvents. We present a detailed study of the molecular mechanism of the photoinduced ICT process in RoLF. For a typical donor-acceptor chromophore, three such mechanisms are discussed in the literature, which differ in the alignment of the donor and acceptor planes, namely planar ICT (PICT), perpendicular-twisted ICT (TICT), and wagging ICT (WICT). Our theoretical results suggest that the TICT mechanism is favored in RoLF.
    The journal of physical chemistry. B. 09/2014;
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    ABSTRACT: It is proposed that xanthophylls, and carotenoids in general, may assist in energy transfer from the chlorophyll Soret band to the Q band. Ground-state (1Ag) and excited-state (1Bu) optimizations of violaxanthin (Vx) and zeaxanthin (Zx) are performed in an environment mimicking the light-harvesting complex II (LHCII), including the closest chlorophyll b molecule (Chl). Time-dependent density functional theory (TD-DFT, CAM-B3LYP functional) is used in combination with a semi-empirical description to obtain the excited-state geometries, supported by additional DFT/multireference configuration interaction calculations, with and without point charges representing LHCII. In the ground state, Vx and Zx show similar properties. At the 1Bu minimum, the energy of the Zx 1Bu state is below the Chl Q band, in contrast to Vx. Both Vx and Zx may act as acceptors of Soret-state energy; transfer to the Q band seems to be favored for Vx. These findings suggest that carotenoids may generally mediate Soret-to-Q energy flow in LHCII.
    ChemPhysChem 09/2014; · 3.35 Impact Factor
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    ABSTRACT: A joint experimental and computational study on the glucose–fructose conversion in water is reported. The reactivity of different metal catalysts (CrCl3, AlCl3, CuCl2, FeCl3, and MgCl2) was analyzed. Experimentally, CrCl3 and AlCl3 achieved the best glucose conversion rates, CuCl2 and FeCl3 were only mediocre catalysts, and MgCl2 was inactive. To explain these differences in reactivity, DFT calculations were performed for various metal complexes. The computed mechanism consists of two proton transfers and a hydrogen-atom transfer; the latter was the rate-determining step for all catalysts. The computational results were consistent with the experimental findings and rationalized the observed differences in the behavior of the metal catalysts. To be an efficient catalyst, a metal complex should satisfy the following criteria: moderate Brønsted and Lewis acidity (pKa=4–6), coordination with either water or weaker σ donors, energetically low-lying unoccupied orbitals, compact transition-state structures, and the ability for complexation of glucose. Thus, the reactivity of the metal catalysts in water is governed by many factors, not just the Lewis acidity.
    Chemistry 08/2014; · 5.93 Impact Factor
  • Ganglong Cui, Walter Thiel
    Journal of Physical Chemistry Letters 07/2014; · 6.59 Impact Factor
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    ABSTRACT: We report the first X-ray structure of a spiroaminal hydrochloride. The chiral spiroaminal crystallizes as a racemic hydrochloride in the monoclinic space group P21/n and adopts the thermodynamically most stable conformation. Density functional calculations on several spiroaminals were used to establish correlations between trends in conformational energies, steric repulsions, and anomeric effects and to reveal the mechanism of the ring-opening tautomerization reaction. In the unsubstituted and backbone-substituted spiroaminals, the aminal tautomer is thermodynamically preferred. N-Substituted spiroaminals favor the amine/imine form for steric reasons, except for those with bridging N,N′ groups. The tautomerization from the aminal to the amine/imine is endergonic and kinetically hindered in the neutral species but quite facile after protonation. Anomeric effects lower the barriers but are less important than steric factors for relative energies.
    European Journal of Organic Chemistry 07/2014; 2014(25):5476-5486. · 3.34 Impact Factor
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    ABSTRACT: Fluorescence emission of wild-type green fluorescent protein (GFP) is lost in the S65T mutant, but partly recovered in the S65T/H148D double mutant. These experimental findings are rationalized by a combined quantum mechanics/molecular mechanics (QM/MM) study at the QM(CASPT2//CASSCF)/AMBER level. A barrierless excited-state proton transfer, which is exclusively driven by the Asp148 residue introduced in the double mutant, is responsible for the ultrafast formation of the anionic fluorescent state, which can be deactivated through a concerted asynchronous hula-twist photoisomerization. This causes the lower fluorescence quantum yield in S65T/H148D compared to wild-type GFP. Hydrogen out-of-plane motion plays an important role in the deactivation of the S65T/H148D fluorescent state.
    Angewandte Chemie 07/2014;
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    ABSTRACT: Fluorescence emission of wild-type green fluorescent protein (GFP) is lost in the S65T mutant, but partly recovered in the S65T/H148D double mutant. These experimental findings are rationalized by a combined quantum mechanics/molecular mechanics (QM/MM) study at the QM(CASPT2//CASSCF)/AMBER level. A barrierless excited-state proton transfer, which is exclusively driven by the Asp148 residue introduced in the double mutant, is responsible for the ultrafast formation of the anionic fluorescent state, which can be deactivated through a concerted asynchronous hula-twist photoisomerization. This causes the lower fluorescence quantum yield in S65T/H148D compared to wild-type GFP. Hydrogen out-of-plane motion plays an important role in the deactivation of the S65T/H148D fluorescent state.
    Angewandte Chemie International Edition 07/2014; · 11.34 Impact Factor
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    ABSTRACT: We report the synthesis of [H2B(pz)2PR]+, [H2C(pz)2PR]+2, [HB(pz)3P]+2, and [HC(pz)3P]+3 (H2B(pz)2=bis(pyrazolyl)borate; H2C(pz)2=bis(pyrazolyl)methane; HB(pz)3=tris(pyrazolyl)borate; HC(pz)3=tris(pyrazolyl) methane; R=Ph, Cy or Et2N) by reaction of the corresponding neutral or anionic ligands with chlorophosphines in the presence of TMSOTf. The structures of these compounds were determined by X‐ray crystallographic analysis and the nature of their bonding was examined using density functional theory. P‐centered (poly)cations stabilized by bis/tris(pyrazolyl)borate/methane ancillary ligands (see figure) can be prepared and structurally analyzed. The highly positive charge at the phosphorous center gives these compounds Lewis acidic character.
    Chemistry 07/2014; 20(28). · 5.83 Impact Factor
  • Daniel Escudero, Walter Thiel
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    ABSTRACT: We report an assessment of the performance of density functional theory-based multireference configuration interaction (DFT/MRCI) calculations for a set of 3d- and 4d-transition metal (TM) complexes. The DFT/MRCI results are compared to published reference data from reliable high-level multi-configurational ab initio studies. The assessment covers the relative energies of different ground-state minima of the highly correlated CrF6 complex, the singlet and triplet electronically excited states of seven typical TM complexes (MnO4 (-), Cr(CO)6, [Fe(CN)6](4-), four larger Fe and Ru complexes), and the corresponding electronic spectra (vertical excitation energies and oscillator strengths). It includes comparisons with results from different flavors of time-dependent DFT (TD-DFT) calculations using pure, hybrid, and long-range corrected functionals. The DFT/MRCI method is found to be superior to the tested TD-DFT approaches and is thus recommended for exploring the excited-state properties of TM complexes.
    The Journal of chemical physics. 05/2014; 140(19):194105.
  • Walter Thiel
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    ABSTRACT: Die exponentiell zunehmende Zahl an Zitationen verdeutlicht das explosive Wachstum der ,,Computational Catalysis“ in den beiden letzten Jahrzehnten. Der Essay skizziert die historische Entwicklung, den jetzigen Stand der Forschung und die zukünftigen Perspektiven auf diesem Gebiet.
    Angewandte Chemie 05/2014;
  • Walter Thiel
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    ABSTRACT: The explosive growth of computational catalysis over the past two decades is reflected by the exponentially increasing number of citations. The Essay traces the historical development, illustrates the current state, and offers comments on the future perspectives of this field.
    Angewandte Chemie International Edition 05/2014; · 11.34 Impact Factor
  • Toru Saito, Walter Thiel
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    ABSTRACT: We report a combined quantum mechanics/molecular mechanics (QM/MM) study on the mechanism of reversible dioxygen binding in the active site of hemocyanin (Hc). The QM region is treated by broken-symmetry density functional theory (DFT) with spin projection corrections. The X-ray structures of deoxygenated (deoxyHc) and oxygenated (oxyHc) hemocyanin are well reproduced by QM/MM geometry optimizations. The computed relative energies strongly depend on the chosen density functional. They are consistent with the available thermodynamic data for oxygen binding in hemocyanin and in synthetic model complexes when using the BH&HLYP hybrid functional with 50% Hartree-Fock exchange. According to the QM(BH&HLYP)/MM results, the reaction proceeds stepwise with two sequential electron transfer (ET) processes in the triplet state followed by an intersystem crossing to the singlet product. The first ET step leads to a non-bridged superoxo CuBII-O2•- intermediate via a low-barrier transition state. The second ET step is even more facile and yields a side-on oxyHc complex with the characteristic Cu2O2 butterfly core, accompanied by triplet-singlet intersystem crossing. The computed barriers are very small so that the two ET processes are expected to very rapid and nearly simultaneous.
    The Journal of Physical Chemistry B 04/2014; · 3.61 Impact Factor
  • Eliot Boulanger, Walter Thiel
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    ABSTRACT: The polarization of the environment can influence the results from hybrid quantum mechanical/molecular mechanical (QM/MM) simulations of enzymatic reactions. In this article, we address several technical aspects in the development of polarizable QM/MM embedding using the Drude Oscillator (DO) force field. We propose a stable and converging update of the DO polarization state for geometry optimizations and a suitable treatment of the QM/MM-DO boundary when the QM and MM regions are separated by cutting through a covalent bond. We assess the performance of our approach by computing binding energies and geometries of three selected complexes relevant to biomolecular modeling, namely the water trimer, the N-methylacetamide dimer, and the cationic bis(benzene)sodium sandwich complex. Using a recently published MM-DO force field for proteins, we evaluate the effect of MM polarization on the QM/MM energy profiles of the enzymatic reactions catalyzed by chorismate mutase and by p-hydroxybenzoate hydroxylase. We find that inclusion of MM polarization affects the computed barriers by about 10%.
    Journal of Chemical Theory and Computation 03/2014; 10(4):1795–1809. · 5.39 Impact Factor
  • You Lu, Zhenggang Lan, Walter Thiel
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    ABSTRACT: The photoexcitation of DNA strands triggers extremely complex photoinduced processes, which cannot be understood solely on the basis of the behavior of the nucleobase building blocks. Decisive factors in DNA oligomers and polymers include collective electronic effects, excitonic coupling, hydrogen-bonding interactions, local steric hindrance, charge transfer, and environmental and solvent effects. This chapter surveys recent theoretical and computational efforts to model real-world excited-state DNA strands using a variety of established and emerging theoretical methods. One central issue is the role of localized vs delocalized excitations and the extent to which they determine the nature and the temporal evolution of the initial photoexcitation in DNA strands.
    Topics in current chemistry 03/2014; · 8.46 Impact Factor
  • Kakali Sen, Walter Thiel
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    ABSTRACT: The P450eryF enzyme (CYP107A1) hydroxylates 6-deoxyerythronolide B to erythronolide B during erythromycin synthesis by Saccaropolysora ertherea. In many P450 enzymes, a conserved "acid-alcohol pair" is believed to participate in the proton shuttling pathway for O2 activation that generates the reactive oxidant (Compound I, Cpd I). In CYP107A1, the alcohol-containing amino acid is replaced with alanine. The crystal structure of DEB bound to CYP107A1 indicates that one of the substrate hydroxyl groups (5-OH) may facilitate proton transfer during O2 activation. We applied molecular dynamics (MD) and hybrid quantum mechanics/molecular mechanics (QM/MM) techniques to investigate substrate-mediated O2 activation in CYP107A1. In the QM/MM calculations, the QM region was treated by density functional theory, and the MM region was represented by the CHARMM force field. The MD simulations suggest the existence of two water networks around the active site, the one found in the crystal structure involving E360 and an alternative one involving E244. According to the QM/MM calculations, the first proton transfer that converts the peroxo to the hydroperoxo intermediate (Compound 0, Cpd 0) proceeds via the E244 water network, with direct involvement of the 5-OH group of the substrate. For the second proton transfer from Cpd 0 to Cpd I, the computed barriers for the rate-limiting homolytic O-O cleavage are similar for the E360 and E244 pathways, and hence both glutamate residues may serve as proton source in this step.
    The Journal of Physical Chemistry B 02/2014; · 3.61 Impact Factor
  • Source
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    ABSTRACT: Supplementary material for: J. Chem. Phys. 123, 134308 (2005) S.N. Yurchenko, J.J. Zheng, H. Lin, P. Jensen, W. Thiel Potential energy surface for the electronic ground state of NH3 up to 20000 cm-1 above equilibrium DOI: 10.1063/1.2047572
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Supplementary material for: J. Chem. Phys. 123, 134308 (2005) S.N. Yurchenko, J.J. Zheng, H. Lin, P. Jensen, W. Thiel Potential energy surface for the electronic ground state of NH3 up to 20000 cm-1 above equilibrium DOI: 10.1063/1.2047572
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Supplementary material for: J. Chem. Phys. 123, 134308 (2005) S.N. Yurchenko, J.J. Zheng, H. Lin, P. Jensen, W. Thiel Potential energy surface for the electronic ground state of NH3 up to 20000 cm-1 above equilibrium DOI: 10.1063/1.2047572
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    ABSTRACT: The purpose of this study was to find flavin derivatives with absorption maxima in the blue-green region of the visible spectrum that might be used as alternative cofactors in blue-light photoreceptors. To this end, the vertical absorption spectra of eight lumiflavin-related compounds were calculated by means of quantum chemical methods. The compounds differ from lumiflavin by the subsitution of an S atom for an O atom at the 2- and/or 4-positions of the isoalloxazine core, the substitution of an N atom for a CH group in the 6- and/or 9-positions, or an extension of the π system at the 7- and 8-positions. For the three most promising compounds, 2-thio-lumiflavin, 4-thio-lumiflavin, and 2,4-dithio-lumiflavin the quantum chemical investigations were extended to include geometry relaxations in the excited states, rates for spin-forbidden transitions and an estimate of spectral shifts brought about by polar protic environments. We find these thiocarbonyl compounds to have very promising excited-state properties. They absorb in the blue-green wavelength regime around 500 nm, i.e., substantially red shifted with respect to lumiflavin that is the cofactor of natural blue-light photoreceptors. Their triplet quantum yields are predicted to be close to unity while their triplet lifetimes are long enough to enable bimolecular photochemical reactions. The combination of these properties makes the thioflavins potentially suitable candidates as cofactors in biomimetic photoswitches.
    The Journal of Physical Chemistry B 01/2014; · 3.61 Impact Factor
  • Computational and Theoretical Chemistry. 01/2014;

Publication Stats

5k Citations
1,652.19 Total Impact Points

Institutions

  • 2000–2014
    • Max Planck Institute for Coal Research
      Mülheim-on-Ruhr, North Rhine-Westphalia, Germany
    • San Diego Supercomputer Center
      San Diego, California, United States
  • 2013
    • University College London
      • Department of Physics and Astronomy
      Londinium, England, United Kingdom
    • Beijing Normal University
      Peping, Beijing, China
  • 2012
    • Chinese Academy of Sciences
      Peping, Beijing, China
  • 2010–2012
    • University of Queensland 
      • Australian Institute for Bioengineering and Nanotechnology
      Brisbane, Queensland, Australia
  • 2008–2011
    • ETH Zurich
      • Laboratory of Physical Chemistry
      Zürich, ZH, Switzerland
    • University of Strathclyde
      • Department of Pure and Applied Chemistry
      Glasgow, SCT, United Kingdom
  • 2008–2010
    • Universität Stuttgart
      Stuttgart, Baden-Württemberg, Germany
  • 1994–2010
    • University of Zurich
      • Institut für Organische Chemie
      Zürich, ZH, Switzerland
  • 1987–2010
    • Bergische Universität Wuppertal
      • • Inorganic Chemistry
      • • Physical and Theoretical Chemistry
      • • Department of Chemistry and Biology
      Wuppertal, North Rhine-Westphalia, Germany
  • 2009
    • University of Glasgow
      • School of Chemistry
      Glasgow, SCT, United Kingdom
    • Industrial University of Santander
      Bucaramanga, Santander, Colombia
  • 2008–2009
    • Technische Universität Dresden
      • Physical Chemistry
      Dresden, Saxony, Germany
  • 2004–2009
    • Hebrew University of Jerusalem
      • • Lise Meitner Minerva Center for Computational Quantum Chemistry
      • • Department of Organic Chemistry
      Jerusalem, Jerusalem District, Israel
    • Max Planck Society
      München, Bavaria, Germany
    • Technische Universität Chemnitz
      • Institute of Chemistry
      Karl-Marx-Stadt, Saxony, Germany
    • Athens State University
      Athens, Alabama, United States
  • 2007–2008
    • University of Wuerzburg
      • Institute of Organic Chemistry
      Würzburg, Bavaria, Germany
    • California Pacific University
      Pinole, California, United States
  • 2005
    • Heinrich-Heine-Universität Düsseldorf
      • Institut für Molekulare Enzymtechnologie (IMET)
      Düsseldorf, North Rhine-Westphalia, Germany
    • University of Bergen
      • Department of Chemistry
      Bergen, Hordaland Fylke, Norway
  • 2004–2005
    • University of Minnesota Twin Cities
      • Department of Chemistry
      Minneapolis, MN, United States
  • 2003–2004
    • University of Georgia
      • Center for Computational Chemistry
      Athens, GA, United States
    • École Polytechnique Fédérale de Lausanne
      • Laboratoire de chimie physique moléculaire
      Lausanne, VD, Switzerland
    • Shanxi Normal University
      Saratsi, Shanxi Sheng, China
  • 2000–2004
    • Friedrich-Alexander Universität Erlangen-Nürnberg
      • Computer-Chemistry-Center
      Erlangen, Bavaria, Germany
  • 2002
    • Universität Heidelberg
      • Interdisciplinary Center for Scientific Computing
      Heidelberg, Baden-Wuerttemberg, Germany
  • 2001
    • Université de Rennes 1
      Roazhon, Brittany, France