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  • Articles  (13)
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  • Articles: DFG German National Licenses  (13)
  • Atomic, Molecular and Optical Physics  (8)
  • Organic Chemistry  (5)
  • 1990-1994  (13)
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  • Articles  (13)
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  • Articles: DFG German National Licenses  (13)
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  • 1
    Electronic Resource
    Electronic Resource
    Eigenvector and eigenvalues of some special graphs. IV. Multilevel circulants (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 105-116 
    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 multilevel circulant is defined as a graph whose adjacency matrix has a certain block decomposition into circulant matrices. A general algebraic method for finding the eigenvectors and the eigenvalues of multilevel circulants is given. Several classes of graphs, including regular polyhedra, suns, and cylinders can be analyzed using this scheme.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560410111
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  • 2
    Electronic Resource
    Electronic Resource
    Net signs of molecular graphs: Dependence of molecular structure (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 87-95 
    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: The concept of internal connectivity associates to each eigenvector of the molecular graph a graph with signed edges. We show that the respective edge signs can be deduced without knowing the graph eigenvectors. The dependence of the edge signs on molecular structure is elucidated. The sign of an edge whose end vertices are νr and νs is found to be the result of separate interactions through all paths connecting the vertices νr and νs. The analysis of the edge signs is particularly simple in the case of acyclic systems. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560490204
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  • 3
    Electronic Resource
    Electronic Resource
    Syntheses of the First Selenium-Containing Bicyclic β -Lactams as Potent Antimicrobial Agents (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1037-1045 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of the cis-configurated isodethiaselenapenam 5 (Scheme 1) as well as the isodethiaselenacephems 29 and 31 (Scheme 2) were accomplished, in which the key step involved addition of Se to the corresponding carbanions of 1, 25, and 27 followed by internal alkylation. β-Lactams 29 and 31 were found to possess biological activity against several pathogenic microorganisms in vitro. The electronic activation of the lactam moiety in the isodethiaselenacephem 31 and the corresponding isocephem 33 remarkably enhanced their biological activity. Isodethiaselenacephem 31 was more toxic than isocephem 33 in experimental animals.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770416
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  • 4
    Electronic Resource
    Electronic Resource
    Efficient Synthesis of Methyl 2-(tert-Butyl)acrylate and Analogous Esters (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1480-1484 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title products are prepared via an efficient three-step synthesis which involves hydroalumination of methyl propiolate and Lewis-acid-promoted reaction with acetone in the presence of BF3 followed by two highly selective SN2′ reactions. The key step is the reaction of 2-(chloromethyl)acrylates with R2CuLi/ZnCl2 reagents which takes place with complete allylic rearrangement.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770603
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of Non-planarity in the Radical Anions of Tribenzo[a,c,e]cyclooctenesDedicated to Prof. Edgar Heilbronner on the occasion of his 70th birthday (1991)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 74 (1991), S. 644-653 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reduction of tribenzo[a,c,e]cyclooctene (2) and its 2,3- and 1,4-dimethyl derivatives (4 and 5), as well as of 1,1-dimethyl-10,11-propane-2,2-diylidene-1H-benzo[5,6]cycloocta[1,2,3,4-def]fluorene (6) and its 5,6-didehydro derivative (7) was followed by cyclic voltammetry. The radical anions of these compounds and those of their derivatives (D)2, (D)5, and (D)6, deuteratsd at C(9) in 1 and 5 or in the corresponding position of 6, have been characterized with the use of ESR, ENDOR, and TRIPLE-resonance spectroscopy. The cyclic-voltammetric and proton-hyperfine data are consistent with the increasing deviations of the radical anions from planarity in the order These deviations, due to steric or interferences in the peri-positions 1↔14 and 4↔5, are removed in and by the introduction of bridging groups. The non-plalarity affects the thermodynamic and kinetic stabilities of the radical anions and causes a shift in the π-spin distribution away from that benzene ring which is linked to the two others by the essential single bonds C(4a)—C(4b) and C(14a)—C(14b). This finding suggests that the steric hindrance in , and is alleviated by twisting this ring out of coplanarity with the remaining (Z)-stilbene-like π-system.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19910740321
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  • 6
    Electronic Resource
    Electronic Resource
    Topological analysis of eigenvalues of particle in one- and two-dimensional simple quantal systems: Net sign approach (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 59-70 
    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: Simple net sign analysis has been carried out for particle in one- and two-dimensional boxes and harmonic oscillators. The conclusion that no simple rule for the ordering of eigenvalues of two-dimensional systems can be drawn is conjectured. Cyclobutadiene, naphthalene, benz-cyclobutadiene, biphenylene, biphenyl, and p-terphenyl are found to behave topologically as particle in either type of potential. Benzene, anthracene, naphthacene, and pentacene are found to behave topologically as particle in a two-dimensional harmonic oscillator. This analysis provides the physical basis for the net sign approach in the signed graph theory.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560390108
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  • 7
    Electronic Resource
    Electronic Resource
    Enantiomers of 11-hydroxy-10-methylaporphine having opposing pharmacological effects at 5-HT1A receptors (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 19-23 
    Details
    ISSN: 0899-0042
    Keywords: aporphine enantiomers ; serotonin 5-HT1A receptors ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two enantiomers of the title compound have been prepared by different synthetic routes. Both bind strongly to 5-HT1A receptors from rat forebrain membrane tissue. However, in a guinea pig ileum preparation, the (R)-enantiomer exhibits properties consistent with its being an agonist, whereas the (S)-enantiomer shows no agonist effect, but it blocks the actions of the (R)-enantiomer and of 8-hydroxy-2-di-n-propylaminotetralin (8-OH-DPAT), a 5-HT1A agonist. These data are presented as a rare example of enantiomers which demonstrate opposite pharmacological effects at the same receptor.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030105
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  • 8
    Electronic Resource
    Electronic Resource
    Applications of molecular dynamics simulations coupled with Harris functional approximation to argon (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 527-537 
    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 demonstrated molecular dynamics simulations using a combination of the classical molecular dynamics with density functional theory for argon clusters. Three different molecular dynamics schemes, which differ in their treatment of the potential energy and forces, have been carried out. The first uses a Lennard-Jones potential. In the second, the potential is computed using the Harris functional, and in the third, a combination of Lennard-Jones and Harris functional potentials is used. In addition to direct examination of the trajectories, the velocity autocorrelation function and its power spectrum have been computed to demonstrate the agreement between these three methods. The present studies show that a scheme that used a combination of model potentials and density functional theory provides a very useful tool for the dynamics simulation of systems that contain some fragments in which the analytical model potentials are not available. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560490415
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  • 9
    Electronic Resource
    Electronic Resource
    Semiempirical calculations of molecular polarizabilities and hyperpolarizabilities of polycyclic aromatic compounds (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 44 (1992), S. 773-784 
    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: The correlation of 2D conjugation and the nonlinear properties of a series of polycyclic aromatic compounds were studied by performing semiempirical calculations using the MOPAC package. For linear polyacenes, both linear and nonlinear properties are found to be increased as the number of six-membered rings increases. In general, the polarizabilities, 〈α〉, and second hyperpolarizabilities, 〈γ〉, are found to correlate very well with total resonance energies. In the case of first hyperpolarizabilities, 〈β〉, symmetry is the dominating factor. © 1992 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560440508
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  • 10
    Electronic Resource
    Electronic Resource
    Quantum chemistry study on B14, B142-, and B14H142- (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 50 (1994), S. 173-179 
    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: The structure of B14, B142-, and B14H142- in octahedral symmetry has been investigated by ab initio calculations at the STO-3G and 4-31G levels. The relationship of molecular orbitals among them has been analyzed and it can be found that the number of valence bonding orbitals of high borane obeys the Wade rule. The similarities and difference between boron clusters and carbon clusters are also discussed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560500302
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