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  • 1
    Digitale Medien
    Digitale Medien
    Valency. II. Applications to molecules with first-row atoms (1983)
    Springer
    Theoretical chemistry accounts 63 (1983), S. 511-527 
    Details
    ISSN: 1432-2234
    Schlagwort(e): Valency of first-row atoms ; Free valence ; Bond indices ; Natural hybrids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A quantum chemical definition of valency proposed in Part I is used to calculate the valency of carbon, nitrogen, oxygen, lithium, beryllium and boron in a number of compounds with the SINDO1 method. It is demonstrated that consistency of the basis set is necessary for comparable results. The general features of valency and bonding in these molecules are discussed. The π-electron concept of free valence is generalised to sigma systems and atoms in molecules are classified as subvalent, normal or hypervalent. The relation between valency and natural hybrid occupancy is illustrated. The symmetry properties of natural hybrid orbitals are discussed by means of group theory. A preliminary attempt is made to relate covalency and covalent reactivity. Bond indices and the σ, π character of bonds are obtained by a suitable partitioning and projection of valency into bonding and antibonding contributions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00552653
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  • 2
    Digitale Medien
    Digitale Medien
    Valency. II. Applications to molecules with first-row atoms (1983)
    Springer
    Theoretical chemistry accounts 63 (1983), S. 511-527 
    Details
    ISSN: 1432-2234
    Schlagwort(e): Valency of first-row atoms ; Free valence ; Bond indices ; Natural hybrids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A quantum chemical definition of valency proposed in Part I is used to calculate the valency of carbon, nitrogen, oxygen, lithium, beryllium and boron in a number of compounds with the SINDO1 method. It is demonstrated that consistency of the basis set is necessary for comparable results. The general features of valency and bonding in these molecules are discussed. The π-electron concept of free valence is generalised to sigma systems and atoms in molecules are classified as subvalent, normal or hypervalent. The relation between valency and natural hybrid occupancy is illustrated. The symmetry properties of natural hybrid orbitals are discussed by means of group theory. A preliminary attempt is made to relate covalency and covalent reactivity. Bond indices and the σ, π character of bonds are obtained by a suitable partitioning and projection of valency into bonding and antibonding contributions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02394810
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  • 3
    Digitale Medien
    Digitale Medien
    Comparative studies on the reactivity of molecules by atomic valences (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 6 (1985), S. 507-513 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: SINDO1 calculations were performed to study the reactivity of molecules with a valence number derived from the density matrix. A comparison of valence numbers was made for selected examples of rotation barriers, substituted strained molecules, radical gas phase reactions, and acid-base reactions. Relations between valence, geometry, and energy changes are discussed.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540060602
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  • 4
    Digitale Medien
    Digitale Medien
    A concept of charge and valence for ab initio wave functions (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 10 (1989), S. 965-974 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: A modified scheme of a previously developed concept of atomic valence numbers in molecules is presented. The relation to population analysis is demonstrated. The scheme is suitable for ab initio wave functions with extended basis sets. The procedure involved a combination of symmetric orthogonalization and contraction of the basis set. The method is used for a systematic investigation of a series of compounds with first-row atoms from Li to F. The predicted atomic charges and valence numbers are in line with results from infrared spectroscopy and multipole moment analysis.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540100802
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  • 5
    Digitale Medien
    Digitale Medien
    SINDO1 study of the photoreaction of tetramethylene sulfone (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 16 (1995), S. 405-413 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: The mechanism of the photoreaction of tetramethylene sulfone (TMSO2) was investigated by the semiempirical molecular orbital (MO) method SINDO1. The relevant low-lying potential energy surfaces, which were calculated with limited configuration interaction (CI), were studied by optimizing intermediates and transition structures and by introducing linear interpolations between these stationary points. The main initial reaction step for all important products is an α cleavage of one C—S bond. This leads to an intermediate that can be classified as an excited singlet diradical. Its electronic structure is described with a two-electron, three-orbital model. Starting from this initially generated intermediate, the reaction branches into several pathways leading to various products. Feasible reaction pathways were established for all important products consistent with experiments. © 1995 by John Wiley & Sons, Inc.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540160403
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  • 6
    Digitale Medien
    Digitale Medien
    Application of SINDO1 to organo-transition metal compounds (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 93-101 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: The recently extended SINDO1 method is used to study geometries, electronic structures, and chemical bonding of transition metal organometallic compounds. The optimized distances and angles between metal atoms and organic ligands are in fair agreement with experimental data and are comparable to ab initio results. The comparison of orbital energies between the current method and ab initio methods shows that the method can give a correct description of electronic structure and bonding patterns of organometallic compounds. The method is also used to calculate atomic and bond valence, which are defined in terms of appropriate combinations of first-order density matrix elements for molecules. The valence indices provide a straightforward and easy-to-interpret way to analyze the magnitude of metal-carbon and metal-metal bonds.
    Zusätzliches Material: 8 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540130112
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  • 7
    Digitale Medien
    Digitale Medien
    Properties of excited states of aromatic rings containing nitrogen (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 410-418 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Quantum chemical calculations with the semiempirical molecular orbital (MO) method SINDO1 were performed on excited states of the following five- and six-membered heterocycles containing nitrogen: imidazol, pyrazol, pyridine, pyridazine, pyrimidine, pyrazine, and s-triazine. The geometries and adiabatic excitation energies of T1, S1, S2 were calculated. We also present charges, bond orders, and dipole moments. Consequences of these results for UV spectroscopic data are discussed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040317
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  • 8
    Digitale Medien
    Digitale Medien
    A unified treatment of valence and bond order from density operators (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 555-561 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: A generalization of the quantum chemical definition of valence of atoms in molecules is suggested. Valence is considered as expectation value of diatomic parts of density operators. It appears as a sum of contributions from occupied orbitals of all atomic pairs that contain the reference atom. This definition is applicable on self-consistent-field (SCF) and configuration interaction (CI) level in any atomic orbitals (AO) basis. Its usefulness is demonstrated in an application to special molecules. Photoelectron spectroscopy and reactivity is discussed in this context.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540050608
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  • 9
    Digitale Medien
    Digitale Medien
    Generalized potential surfaces under inclusion of nuclear motion (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 8 (1987), S. 350-357 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: A new method for the solution of the vibronic Schrödinger equation is presented. The proposed approach allows the preservation of the concept of potential surfaces under inclusion of nuclear motion. The dynamical interaction of electrons and nuclei is partially included in the equation determining the potential surfaces. The corresponding electronic wave functions can be used as a basis for a generalized representation. Since the variation principle is involved for the determination of the potential surfaces, the proposed representation may be considered as a generalization of the adiabatic one. As a consequence the vibrational wave equation and the calculation of radiationless transition probabilities is simplified.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540080411
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  • 10
    Digitale Medien
    Digitale Medien
    Application of SINDO1 to sulphur compounds (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 8 (1987), S. 1004-1015 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: SINDO1 calculations are presented for ground state geometries, heats of formation, ionization potentials and dipole moments. These calculations are based on a new parametrization of SINDO1 for second-row elements which features inclusion of 3d orbitals and zero point energies. The comparison shows an improvement over MNDO, especially for hypervalent sulphur compounds.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540080709
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