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  • Atomic, Molecular and Optical Physics  (6)
  • Density functional calculations  (2)
  • INDO method for lanthanides  (2)
  • Organic Chemistry  (2)
  • Transition states  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Relativistic density-functional studies of naked and ligated gold clusters (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 595-610 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electronic structure investigations on a broad range of gold compounds, including naked and ligated gold clusters, are reviewed. The calculations have been carried out with a recently introduced relativistic variant of the linear combination of Gaussian-type orbitals density-functional (LCGTO-DF) method which affords all-electron investigations for very large systems. The accuracy of the method will be evaluated for the gold dimer. Then the electronic structure of the naked cluster Au55 is studied, both in Ih and Oh symmetry. Nonrelativistic and relativistic results obtained by the present method are compared to those of the much simpler jellium model. Since triphenylphosphine is among the most common ligands in gold chemistry a series of mononuclear gold phosphine compounds MeAuPR3 with increasingly complex ligands PR3 (R = H, CH3, C5H6) is discussed. The calculations reveal the success and the limitations of simpler phosphines often employed as model ligands in theoretical studies. Some aspects of the phosphine gold interaction in these simpler compounds carry over to the main group element centered gold clusters. Thereby one arrives at a rationalization of the particularly high stability of the carbon-centered octahedral cluster cation [(R3PAu)6C]2+ as compared to the neighboring isoelectronic boron and nitrogen-centered clusters. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520853
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  • 2
    Electronic Resource
    Electronic Resource
    An intermediate neglect of differential overlap (INDO) technique for lanthanide complexes: studies on lanthanide halides (1987)
    Springer
    Theoretical chemistry accounts 71 (1987), S. 21-39 
    Details
    ISSN: 1432-2234
    Keywords: INDO method for lanthanides ; Lanthanide halides ; Ce(NO3)6 2−
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An intermediate neglect of differential overlap method of use for examining the electronic structure of lanthanide complexes is developed. It is characterized by a basis set obtained from relativistic Dirac-Fock atomic calculations, the inclusion of all one-center two-electron integrals, and a parameter set based on molecular geometry. Lanthanide halides MX2, MX3 and MX4 are studied here, as well as initial results for the twelve coordinate Ce(NO3)6 −2 ion. Geometries obtained are in excellent agreement with experimental values when available. Many MX3 complexes are found to be pyramidal, and EuCl2 and YbCl2 are calculated to be bent even at the SCF level. Models invoking London type forces are therefore not required. Ionization potentials are calculated for the trihalides (δSCF) and are in reasonable agreement with experiment. Contrary to conclusion of others, f-orbital participation, although small, is required — at least in this model — to obtain the spread of metal to halide bond distance observed in these complexes. However f-orbital participation does not seem to be significant even in the twelve coordinate Ce(NO3)6 −2 complex: rather the large coordination number seems to be a consequence of the relatively large size of the lanthanide ion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00538479
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  • 3
    Electronic Resource
    Electronic Resource
    Intermediate neglect of differential overlap spectroscopic studies on lanthanide complexes (1992)
    Springer
    Theoretical chemistry accounts 81 (1992), S. 201-222 
    Details
    ISSN: 1432-2234
    Keywords: INDO method for lanthanides ; Spin-orbit interaction ; Electronic spectra ; Lanthanide monoxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The Intermediate Nelgect of Differential Overlap model for spectroscopy has been extended to lanthanide complexes by including spin-orbit coupling. The method uses atomic spectroscopy and model Dirac-Fock calculations on the lanthanide atoms and ions to obtain ionization potentials, Slater-Condon factors and basis sets. The spin-orbit interaction strength, ζ(nl), is acquired from atomic spectroscopy, and only one-center terms are formally included. Calculation then proceeds using one open-shell operator for all sevenf-orbitals initially assumed degenerate to generate starting non-relativistic molecular orbitals for the subsequent configuration-interaction and spin-orbit calculation. Calculations are performed on the monoxides La, Ce, Gd, and Lu where there are ample experimental assignments. In general, the results are quite good, suggesting that the calculated energies, oscillator strengths and spin-orbit splittings can be used with success in assigning spectra, even in those cases wherejj-coupling is of intermediate strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01118562
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  • 4
    Electronic Resource
    Electronic Resource
    Density Functional Studies on Amino-Substituted Methane and Silane (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1745-1749 
    Details
    ISSN: 0009-2940
    Keywords: Density functional calculations ; Tetra(amino)methane ; Tetra(amino)silane ; Transition states ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In all-electron density functional calculations on mono- and tetraaminosubstituted methane and silane the coordination around the nitrogen center is found, in complete agreement with experiment, to be less pyramidal in the silicon compounds. The calculated barrier to inversion at nitrogen is only 0.6 kcal/mol in silylamine, while in methylamine it is 5.5 kcal/mol. The larger flexibility is attributed to the greater ionic character of the Si-N bond compared to that of the C-N bond. In tetra(amino)methane, inversion of one amino group leads to a local minimum (calculated inversion barrier: 6.4 kcal/mol), while a corresponding structure (or barrier) does not exist for the silicon compound. Due to the steric influence of the amino groups, the barrier to rotation around the C-N bond is larger in the tetrasubstituted compound (6.4 kcal/mol compared to 2.3 kcal/mol in methylamine). While the average binding energy of the amino groups is similar in both tetra(amino)compounds, the binding energy of the fourth ligand is about 25% larger in the silicon compound for both homolytic and heterolytic bond cleavage. This difference arises from the relative stabilization of the tri(amino)-methyl species, due to some n contribution to the C-N bond.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301207
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  • 5
    Electronic Resource
    Electronic Resource
    Rotations, quaternions and double groups. By Simon L. Altmann, Clarendon Press, Oxford, 1986, 317 pp. (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 401-401 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560320310
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  • 6
    Electronic Resource
    Electronic Resource
    Toward a chemisorption cluster model using the LCGTO-Xα method: Application to Ni(100)/Na (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 275-285 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A modified cluster approach for modeling local chemisorption phenomena is suggested on the basis of the linear combination of Gaussian-type orbitals (LCGTO) Xα method. Contractions of the fitting bases are employed to take into account the reduced polarizability of a surface cluster and to access larger cluster sizes. Furthermore, embedding of a cluster in the surface is mimicked by Gaussian broadening of the one-electron levels leading to fractional occupation numbers via a self-consistently determined Fermi energy of the cluster. As a first application results are presented for the clusters NinNa (n = 5, 9, 17) modeling the low coverage limit of the chemisorption system Ni(100)/Na. Calculated bond length, binding energy, and induced “surface” dipole moment show fair agreement with experimental values, indicating a substantial covalent character of alkali bonding on transition metal surfaces even in the zero coverage limit.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560340832
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  • 7
    Electronic Resource
    Electronic Resource
    An INDO/S-CI treatment including spin-orbit interaction based on Rumer spin functions. Application to the hydrated cerium ion (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 40 (1991), S. 545-555 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We examine the inclusion of spin-orbit effects within the Rumer configuration interaction technique and discuss its implementation in the spectroscopic version of the intermediate neglect of differential overlap model (INDO/S-CI). An efficient strategy for calculating excitation energies, transition moments, and Mulliken populations for Rumer-adapted functions is described. As an example, results are presented for the ground and excited states of the hydrated trivalent cerium ion [Ce(H2O)9]3+, which confirm the low energy assignments to 4ƒ → 5 d transitions split by some 10000 cm-1 through spin-orbit coupling and ligand field interaction. Comparisons are made between this technique and one that we have used previously that utilizes configuration interaction over double-group adapted linear combinations of determinants.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560400848
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  • 8
    Electronic Resource
    Electronic Resource
    Activity of Peroxo and Hydroperoxo Complexes of TiIV in Olefin Epoxidation: A Density Functional Model Study of Energetics and Mechanism (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2135-2145 
    Details
    ISSN: 1434-1948
    Keywords: Density functional calculations ; Epoxidation ; Peroxo complexes ; Titanium ; Transition states ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Epoxidation of olefins by TiIV peroxo and hydroperoxo (alkylperoxo) complexes was investigated using a hybrid DFT method (B3LYP). Reaction energies and activation barriers for direct oxygen transfer to ethylene as a model olefin were computed for various model complexes to compare the epoxidation activity of Ti(η2-O2) and TiOOR (R = H, CH3) moieties. The activity of complexes with a Ti(O2) peroxo group is shown to be essentially quenched when the coordination sphere of the complex is saturated by strongly basic (σ-donor) ligands. In contrast, the activity of a TiOOH functional group depends only weakly on the saturation of the coordination sphere of the Ti center. Substitution of methyl for hydrogen in a TiOOH group is found to slightly increase the activation barrier of epoxidation. The computational results give preference to reaction paths that involve TiOOR species. The factors governing the activity of Ti(O2) and TiOOR groups, in particular the effects of donor ligands, are discussed on the basis of a molecular orbital analysis.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Electronic and magnetic properties of organometallic clusters: From the molecular to the metallic state (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 44 (1992), S. 605-619 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have performed a linear combination of Gaussian-type orbitals, LCGTO, local density functional, LDF, calculations on a series of low- and high-nuclearity carbonylated Ni clusters and on their naked counterparts. We have found that while the bare Ni clusters do exhibit several features in common with the bulk metal, the low-nuclearity carbonylated clusters do not show any metallic behavior. Signs of a developing metallic character are found for high-nuclearity Ni cluster carbonyls where it is possible to distinguish between “surface” atoms, which are directly interacting with the ligand sphere, and “bulk” atoms, which are only interacting with other metal atoms. Through the analysis of the magnetic properties of these systems it is possible to formulate a general model which rationalizes both the metallic behavior of the free Ni clusters and the nonmetallic behavior in certain carbonylated Ni clusters. This model is based on the perturbations induced by the ligands on the electronic structure of the metal atoms in the cluster. © 1992 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560440854
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  • 10
    Electronic Resource
    Electronic Resource
    Darstellung, Tautomerieverhalten und Wasserstoffbrücken-bindung von 2-Heteroarylamino-thiazolen (1975)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 317 (1975), S. 953-958 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis, Tautomeric Properties, and Hydrogen Bonds of 2-Heteroarylamino-thiazoles2-Heteroarylamino-thiazoles have been prepared by the method of HANTZSCH from heteroaryl-substituted thioureas. UV and IR spectra indicate the amino form for these compounds. In solid state, they are associated through N—H…N bonds, the nitrogen atom of the thiazole ring serving as an acceptor of protons.
    Notes: 2-Heteroarylamino-thiazole lassen sich nach der Methode von HANTZSCH aus heteroaromatisch substituierten Thioharnstoffen darstellen. Die UV- und IR-spektroskopische Untersuchung zeigt, daß diese Verbindungen in der Aminoform vorliegen. Sie sind im festen Zustand über N—H…N-Brücken assoziiert, wobei das Ringstickstoffatom des Thiazols als Protonenakzeptor fungiert.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19753170611
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