Michael Dolg

University of Cologne, Köln, North Rhine-Westphalia, Germany

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Publications (260)782.24 Total impact

  • Hongjuan Wang · Xiaoyan Cao · Xuebo Chen · Weihai Fang · Michael Dolg
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    ABSTRACT: The asymmetric catalysis of the intramolecular enone [2+2] photocycloaddition has been subject of extensive experimental studies, however theoretical insight to its regulatory mechanism is still sparse. Accurate quantum chemical calculations at the CASPT2//CASSCF level of theory associated with energy-consistent relativistic pseudopotentials provide a basis for the first regulation theory that the enantioselective reaction is predominantly controlled by the presence of relativistic effects, that is, spin-orbit coupling resulting from heavy atoms in the chiral Lewis acid catalyst.
    No preview · Article · Oct 2015 · Angewandte Chemie International Edition
  • Michael Dolg · Oliver Mooßen
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    ABSTRACT: The sandwich complex bis(η8-pentalene)cerium Ce(C8H6)2 was investigated by relativistic quantum chemical ab initio methods and the nature of the interaction between the Ce 4f and ligand π orbitals was analyzed. It is shown for a multi-configurational ground state wavefunction of the complete active space variety that by means of an orbital rotation in the space of the strongly interacting orbitals it is possible to generate nearly pure Ce 4f and ligand π orbitals without changing the total energy. These orbitals are occupied by one electron each, leading to an open-shell 4f1π1 ground state configuration. The admixture of the energetically higher closed-shell 4f0π2 configuration leads to a singlet ground state, making the complex another example for a molecular analog of a Ce(III)-based lattice Kondo system. A further analysis using local spin and occupation number fluctuations in a two-electron two-orbital description reveals that the Ce 4f-ligand π interaction corresponds to a significantly stretched covalent bond: orbital and configuration mixing coefficients as well as local spin and occupation number fluctuations are very similar to those of hydrogen dimer H2 at an interatomic distance of about two times the equilibrium distance.
    No preview · Article · Oct 2015 · Journal of Organometallic Chemistry
  • Oliver Mooßen · Michael Dolg
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    ABSTRACT: The geometric and electronic structures of bis(cyclopentadienyl)cerium compounds of the type Cp2CeZ (Z=CH2, CH-, NH, O, F+) are analyzed paying special attention to the terminal metal-ligand multiple bonding in the CeZ units. Complete active space self-consistent field calculations were performed, followed by unitary transformations in the active orbital space in order to monitor the weights of the leading configurations, as well as the Ce and Z character of the orbitals. It is shown that all compounds, except the closed-shell Ce(IV) complex Cp2CeF+, have an open-shell singlet ground state and the 4f orbitals are important for their electronic structure. In case of Z=CH2, CH- the singlet ground state consists to more than 90% of the Cefπ1Zpπ1 configuration when using nearly pure cerium 4f and carbon 2p orbitals of the Z group, implying Ce(III) systems. In contrast, the systems containing Z=NH, O revealed a more mixed Ce(III)/Ce(IV) ground state wavefunction. The interactions of the active orbitals were characterized by calculating the expectation values of the charge fluctuation operator and the local spin operator. The results are evaluated by comparison with the values achieved by stretching the covalent bond of a H2 molecule. The CH2 and the CH- complexes show, besides a CeZ σ bond, a quite weak covalent Ce fZ p orbital interaction in π symmetry, while the other two complexes (Z=NH, O) exhibit a stronger covalent interaction with a noticeable ionic character because of the higher electronegativities of nitrogen and oxygen.
    No preview · Article · Sep 2015 · Computational and Theoretical Chemistry
  • Jun Zhang · Michael Dolg
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    ABSTRACT: Global optimization of cluster geometries is of fundamental importance in chemistry and an interesting problem in applied mathematics. In this work, we introduce a relatively new swarm intelligence algorithm, i.e. the artificial bee colony (ABC) algorithm proposed in 2005, to this field. It is inspired by the foraging behavior of a bee colony, and only three parameters are needed to control it. We applied it to several potential functions of quite different nature, i.e., the Coulomb-Born-Mayer, Lennard-Jones, Morse, Z and Gupta potentials. The benchmarks reveal that for long-ranged potentials the ABC algorithm is very efficient in locating the global minimum, while for short-ranged ones it is sometimes trapped into a local minimum funnel on a potential energy surface of large clusters. We have released an efficient, user-friendly, and free program "ABCluster" to realize the ABC algorithm. It is a black-box program for non-experts as well as experts and might become a useful tool for chemists to study clusters.
    No preview · Article · Sep 2015 · Physical Chemistry Chemical Physics
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    ABSTRACT: The experimentally observed extraction complexes of trivalent lanthanide Eu(3+) and actinide Am(3+)/Cm(3+) cations with Cyanex272 [bis(2,4,4-trimethylpentyl) phosphinic acid, denoted as HC272] and Cyanex301 [bis(2,4,4-trimethylpentyl) dithiophosphinic acid, denoted as HC301] have been studied by using relativistic energy-consistent 4f- and 5f-in-core pseudopotentials for trivalent f elements, combined with density functional theory and a continuum solvation model. It has been found that, as a result of hydrogen bonding, HC272 exists primarily as a self-associated species, whereas HC301 is preferably a monomer. The calculations show that in case of all three M(3+) (M=Eu, Am, Cm) ions for HC272 the extraction complexes M[H(C272)2]3 are formed prior to M(C272)3, whereas for HC301 the extraction complexes M(C301)3 have priority over M[H(C301)2]3. The calculated M-O and M-S bond lengths and the M-P distances of these prefered extraction complexes agree very well with the available experimental data. The obtained changes of the Gibbs free energies in the liquid-liquid extraction reactions (1): M(3+)aqu + 3(HC272)2,org --> M[H(C272)2]3,org + 3H(+)aqu} and (2): M(3+)aqu} + 3HC301,org --> M(C301)3,org + 3H(+)aqu agree with the experimentally observed thermodynamical priority of HC272 and HC301, i.e., HC272 prefers Eu(3+) over Am(3+)/Cm(3+) and HC301 prefers Am(3+)/Cm(3+) over Eu(3+). The obtained changes of Gibbs free energies in reaction (2) (Eu, 68.10 kJ/mol; Am, 46.50 kJ/mol) agree quite well with the experimental findings (Eu, 63.3 kJ/mol; Am, 44.1 kJ/mol).
    No preview · Article · Jul 2015 · Physical Chemistry Chemical Physics
  • Norah Heinz · Michael Dolg · Albrecht Berkessel
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    ABSTRACT: A detailed theoretical study of the mechanism and energetics of an organocatalysis based on CN activation by halogen-bonding is presented for the hydrocyanation of N-benzylidenemethylamine. The calculations at the level of scalar-relativistic gradient-corrected density functional theory give an insight in this catalytic concept and provide information on the characteristics of four different monodentate catalyst candidates acting as halogen-bond donors during the reaction. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.
    No preview · Article · Jul 2015 · Journal of Computational Chemistry
  • Jun Zhang · Michael Dolg
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    ABSTRACT: The third-order incremental dual-basis set zero-buffer approach (inc3-db-B0) is an efficient, accurate and black-box quantum chemical method for obtaining correlation energies of large systems, and has been successfully applied to many real chemical problems. In this work we extend this approach to high-spin open-shell systems. In the open-shell approach we will first decompose the occupied orbitals of a system into several domains by a K-means clustering algorithm. The essential part is that we preserve the active (singly occupied) orbitals in all the calculations of the domain correlation energies. The duplicated contributions of the active orbitals to the correlation energy are subtracted from the incremental expansion. All techniques of truncating the virtual space such as the B0 approximation can be applied. This open-shell inc3-db-B0 approach is combined with the CCSD and CCSD(T) methods and applied to the computations of a singlet-triplet gap and an electron detachment process. Our approach exhibits an accuracy better than 0.6 kcal/mol or 0.3 eV compared with the standard implementation, while it saves a large amount of the computational time and can be efficiently parallelized.
    No preview · Article · Mar 2015 · Journal of Chemical Theory and Computation
  • Michael Dolg
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    ABSTRACT: This chapter describes some important aspects of the shell structure, relativistic effects, and electron correlation effects for lanthanide and actinide atoms and molecules, mainly using the example of Cerium (Ce) and Thorium (Th). It turns to a discussion of the electronic structure of cerium-bis(η8-cyclooctatetraene), cerocene, which fascinated this author for more than two decades, as well as a related cerium (III) -based molecular Kondo system, i.e., bis(η8-pentalene) cerium. These systems feature many problems of an accurate relativistic correlated description of their electronic structure and moreover leave plenty of room for alternative interpretations of their electronic ground state as well as the involvement of 4f orbitals in chemical bonding. In order to describe accurately the electronic structure of many-electron systems, highly correlated approximate solutions of the Schrödinger equation built from the best possible relativistic Hamiltonian are needed.
    No preview · Chapter · Feb 2015
  • Michael Dolg
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    ABSTRACT: For a wide range of trivalent lanthanide ion coordination complexes of tricapped trigonal prism or monocapped square antiprism configurations, the bonds between the central lanthanide ions and the capping ligands are found to violate Badger's rule: they can get weaker as they get shorter. We demonstrate that this observation originates from the screening and repulsion effect of the prism ligands. Both effects enhance as the electric field of the central ion or the softness of the prism ligands increases. Thus for heavier lanthanides despite that the capping bond could be shorter, it is more efficient to be weakened by the prism ligands, being inherently labile. This concept of "labile capping bonds phenomenon" is then successfully used to interpret many problems in lanthanide(III) hydration, e.g. why the water exchange rate of a lanthanide(III) complex is much higher in twisted square antiprism than in square antiprism configuration. Thus the theory proposed in this paper offers new insights in understanding chemical problems.
    No preview · Article · Dec 2014 · The Journal of Physical Chemistry A
  • Norah Heinz · Jun Zhang · Michael Dolg
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    ABSTRACT: The Gibbs energies of hydration of actinoid(III) ions are evaluated for density functional optimized geometries of [An(H2O)h]3+ complexes (h = 8, 9) at the coupled cluster singles, doubles, and perturbative triples level by means of the incremental scheme. Scalar-relativistic 5f-in-core pseudopotentials for actinoids and basis sets of polarized triple-ζ quality were applied. The calculated Gibbs energies for the octa- and nona-aquo complexes agree within 1% with the experimental values which are available only for uranium and plutonium. Compared to the hydrate complexes of the lanthanoid(III) ions those of the actinoid(III) series are slightly less stable.
    No preview · Article · Dec 2014 · Journal of Chemical Theory and Computation
  • Tim Hangele · Michael Dolg
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    ABSTRACT: The bond length and dissociation energy of the Copernicium dimer calculated at different levels of theory are presented. The coupled-cluster and the density functional method are used in fully relativistic four-component all-electron calculations and two-component calculations using effective core potentials, which include the Breit contribution and quantum electrodynamic effects. The results show the importance of the spin–orbit coupling and also the Gaunt/Breit contribution, which could be easily included in the pseudopotential calculations. Additionally, a reversal in the trend of the bonding of the group 12 dimers could be shown by analyzing the charge fluctuation and local spin expectation values.
    No preview · Article · Nov 2014 · Chemical Physics Letters
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    Dataset: JCP08734

    Full-text · Dataset · Oct 2014
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    ABSTRACT: In this paper we present ab initio many-body calculations on the strain energy of W silica, taken as a model system for edge-sharing tetrahedral SiO2 systems with respect to corner-sharing ones as in a quartz. The mean-field results were obtained using the restricted Hartree–Fock approach, while the many-body effects were taken into account by the second-order Møller–Plesset perturbation theory and the coupled-cluster approach. Correlation contributions are found to play an important role to determine the stability of edge-sharing units. The most sophisticated method used in our calculation, i.e., the coupled-cluster approach with single and double excitations, yields a strain energy of 0.0427 a.u. per Si2O4 unit with respect to a quartz, which is even smaller than the value obtained by a previous density functional theory calculation.
    Full-text · Dataset · Oct 2014
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    Jun Zhang · Michael Dolg
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    ABSTRACT: By state-of-the-art quantum chemical methods, we show that for bulky functional groups like cyclohexane, [20]fullerene, dodecahedrane, and C60, the attractive dispersion interaction can have a greater impact on stereochemistry than the repulsive steric effect, making the compact isomer the more stable one. In particular, for the double C60 adduct of pentacene 1, the syn isomer should be the main product instead of the anti one inferred in the original synthesis experiment (Y. Murata et al., J. Org. Chem.­ 1999, 64, 3483). With and without dispersion interactions taken into account, the Gibbs energy difference ΔG(syn−anti) is −6.36 and +1.15 kcal mol−1, respectively. This study reminds us that dispersion interactions as well as electrostatic or hyperconjugation effects, etc. can lead to some unusual stereochemical phenomena.
    Full-text · Article · Oct 2014 · Chemistry - A European Journal
  • Jun Zhang · Norah Heinz · Michael Dolg
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    ABSTRACT: The hydration of all trivalent lanthanoid (Ln) ions is studied theoretically from two aspects: energy and wave function. With the help of the incremental scheme, for the first time the lanthanoid(III) aqua complexes are computed at the CCSD(T) level using large basis sets. These computations prove that SCS-MP2 is nearly as accurate as CCSD, thus enabling us to give the most accurate first principle hydration Gibbs free energies and reliable preferred coordination numbers (CNs) of lanthanoid(III) aqua complexes: 9, 8, and both, for light, heavy, and intermediate lanthanoids, respectively. Then a series of wave function analyses were performed to explore the deeper reasons for the preference of specific CNs. An unexpected observation is that as Ln goes from samarium to lutetium, the capping Ln-O bonds in nona-aqua lanthanoid complexes become weaker while they get shorter. Therefore, as the capping Ln-O bonds are getting easier to disrupt, heavier lanthanoids will prefer a low CN, i.e., 8. On the basis of this and previous work of other groups, a model for the water exchange kinetics of lanthanoid(III) ions is proposed. This model suggests that the capping Ln-O bonds of moderate strength, which occur for intermediate lanthanoids, are advantageous for the formation of a bicapped trigonal prism intermediate during water exchange. This explains some NMR experiments and, more importantly, an observation which puzzled investigators for a long time, i.e., that the exchange rate reaches a maximum for the middle region but is low at the beginning and end of the lanthanoid series. This nontrivial behavior of capping Ln-O bonds is interpreted and is believed to determine the hydration behavior of lanthanoid(III) ions.
    No preview · Article · Jun 2014 · Inorganic Chemistry
  • Michael Dolg · Xiaoyan Cao · Jan Ciupka
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    ABSTRACT: In complexes of trivalent Eu and Am standard unrestricted Kohn-Sham density functional calculations tend to yield shorter bond distances for the Am-X than for the Eu-X bonds, especially when X is a so called soft ligand. Since the ionic radius of Am-III is larger than the one of Eu-III the reversed order of the bond distances is sometimes explained by a higher covalency of the Am-X bond compared to the one of the Eu-X bond. A comparison of density functional with wavefunction-based correlated calculations for several model systems reveals, however, that the energetically low-lying and spatially compact 4f shell of Eu-III often is erroneously filled with significantly more than 6 electrons at the density functional theory level, thus yielding considerably too long bond distances. Particularly claims based on comparisons of structures optimized at the density functional level that the strong preference of the Cyanex 301 ligand for Am-III over Eu-III is due to an increased covalency in the Am-S bonds should be viewed with some reservation.
    No preview · Article · Jun 2014 · Journal of Electron Spectroscopy and Related Phenomena
  • Anna Weigand · Xiaoyan Cao · Tim Hangele · Michael Dolg
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    ABSTRACT: Small-core pseudopotentials for actinium, thorium, and protactinium have been energy-adjusted to multi-configuration Dirac--Hartree--Fock reference data based on the Dirac--Coulomb--Breit Hamiltonian and the Fermi nucleus model. Corresponding optimized valence basis sets of polarized valence quadruple-zeta quality are presented. Atomic test calculations for the first four ionization potentials show satisfactory results at both the Hartree--Fock as well as the multi-reference averaged coupled-pair functional level. Highly-correlated Fock-space coupled cluster calculations demonstrate that the new pseudopotentials yield ionization potentials, which are in excellent agreement with corresponding all-electron results and experimental data. The pseudopotentials and basis sets supplement a similar set previously published for uranium.
    No preview · Article · Mar 2014 · The Journal of Physical Chemistry A
  • Oliver Mooßen · Michael Dolg
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    ABSTRACT: Two alternative interpretations are given for the electronic ground state of bis-η8-annulene[8] cerium, cerocene, based on the same relativistic Douglas-Kroll-Hess complete active space all-electron wavefunction. Rotations in the spaces of the one- and many-electron wavefunctions, leaving the total energy invariant, show that the system can be viewed as a complex of a closed-shell Ce(IV) ion sandwiched by two aromatic annulene[8] dianions and bonded with a significant Ce 4f - ring π covalency, or as a Ce(III) ion with an almost atomic-like 4f1 subconfiguration, coupled to the unpaired electron in the rings highest energy occupied π orbitals in a Kondo-type fashion.
    No preview · Article · Feb 2014 · Chemical Physics Letters
  • Jun Zhang · Michael Dolg
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    ABSTRACT: The third-order incremental dual-basis set zero-buffer approach was combined with CCSD(T)-F12x (x = a, b) theory to develop a new approach, i.e., the inc3-db-B0-CCSD(T)-F12 method, which can be applied as a black-box procedure to efficiently obtain the near complete basis set (CBS) limit of the CCSD(T) energies also for large systems. We tested this method for several cases of different chemical nature: four complexes taken from the standard benchmark sets S66 and X40, the energy difference between isomers of water hexamer and the rotation barrier of biphenyl. The results show that our method has an error relative to the best estimation of CBS energy of only 0.2 kcal/mol or less. By parallelization, our method can accomplish the CCSD(T)-F12 calculations of about 60 correlated electrons and 800 basis functions in only several days, which by standard implementation are impossible for ordinary hardware. We conclude that the inc3-db-B0-CCSD(T)-F12a/AVTZ method, which is of CCSD(T)/AV5Z quality, is close to the limit of accuracy that one can achieve for large systems currently.
    No preview · Article · Dec 2013 · The Journal of Chemical Physics
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    ABSTRACT: Not only σ*σ but also σ*π: High-level electronic structure calculations reveal the σ*σ and σ*π bonding patterns for Au(I) -Au(I) bonding in excited states and suggest two conformation-dependent photophysical relaxation mechanisms for dicyanoaurate oligomers (n=2-5; see picture) in aqueous solution. These insights into the excited-state electronic structure should also be relevant for other gold complexes with a similar gold scaffold.
    No preview · Article · Sep 2013 · Angewandte Chemie International Edition

Publication Stats

20k Citations
782.24 Total Impact Points

Institutions

  • 2003-2015
    • University of Cologne
      • Institute for Theoretical Chemistry
      Köln, North Rhine-Westphalia, Germany
  • 2000-2010
    • University of Bonn
      • • Institute for Inorganic Chemistry
      • • Institute of Physical and Theoretical Chemistry
      Bonn, North Rhine-Westphalia, Germany
  • 1995-2002
    • Max Planck Institute of Physics
      München, Bavaria, Germany
  • 1995-2000
    • Max Planck Institute for Dynamics of Complex Technical Systems
      Magdeburg, Saxony-Anhalt, Germany
  • 1999
    • Max Planck Institute for the Physics of Complex Systems
      Dresden, Saxony, Germany
  • 1983-1995
    • Universität Stuttgart
      • Institute of Theoretical Chemistry
      Stuttgart, Baden-Wuerttemberg, Germany
  • 1989
    • Universität Siegen
      Siegen, North Rhine-Westphalia, Germany