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  • 1
    Electronic Resource
    Electronic Resource
    Structure and properties of non-classical polymers (1993)
    Springer
    Theoretical chemistry accounts 86 (1993), S. 353-367 
    Details
    ISSN: 1432-2234
    Keywords: High-spin non-alternant polymers ; Nature of spin exchange interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The investigations on alternant non-classical (non-Kekulé) polymers [1, 2] (ANCP) have been extended to a class of quasi-one-dimensional non-alternant non-classical polymers (NANCP). The energy spectra and the effective spin exchange between the unpaired electrons in the NANCP are investigated theoretically. As for the ANCP, the energy spectrum of the NANCP is characterized by a wide energy gap in which there is a half-filled band (HFB) of degenerate non-bonding molecular orbitals (NBMO). The occurrence of a NBMO is a topological property of the considered non-alternant systems, and is explained with an approach which originates from the Sachs theorem. The effective spin exchange interaction within the HFB of a wide variety of model polymers was calculated. It is shown that the potential (Coulomb) and the indirect exchange interaction (superexchange) are the main components of the effective ferromagnetic interaction. The ground state of the 1D-NANCP is a high-spin one, as in the case of the ANCP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01128522
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  • 2
    Electronic Resource
    Electronic Resource
    On alternant molecules with identical energy spectra: Isospectral molecules (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 167-169 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that if a pair of alternant molecules are isospectral (they have identical energy spectra) in the topological - Hückel - approximation they are also isospectral, taking into account the electron correlation. The proof is given in the AMO approximation using a Hubbard Hamiltonian. © 1997 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Quantenchemische Untersuchungen an Farbstoffaggregaten. I. Allvalenzelektronen-SCF-Berechnungen am Trimethincyanin und Doppelmolekülmodellen (1971)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 313 (1971), S. 1101-1109 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mit einem Allvalenzelektronen-SCF-Verfahren - der INDO-Methode - wird die Elektronenstruktur des Tri- und Pentamethincyanins untersucht. An ausgewählten Modellen wird für die möglichen geometrischen Anordnungen der Trimethincyanin-Einzelmoleküle in Doppelmolekülen die relative energetische Stabilität abgeschätzt. Die Berechnungen bestätigen die schon früher festgestellte starke Ladungsalternation und einen weitestgehenden Bindungsausgleich entlang der Polymethinkette. Die Elektronendichteverteilung wird duch die Zusammenlagerung von Trimethincyaninmolekülen zu Doppelmolekülen wenig verändert. Das Modell mit einer „mauerwerkartigen“ Anordnung erweist sich als das stabilste.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19713130614
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  • 4
    Electronic Resource
    Electronic Resource
    78. Planungsphasenorientierte Kostenschätzung von Chemieanlagen (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 990-990 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710982
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  • 5
    Electronic Resource
    Electronic Resource
    NMR-Untersuchungen an Polymethinfarbstoffen und Farbstoffzwischenprodukten. III. Zur Reaktivität der 2-Methylcycloammoniumsalze (1973)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 315 (1973), S. 600-610 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Zur Abschätzung der Reaktivität der 2-Methylcycloammoniumsalze wurden die 1H-NMR-Spektren der Verbindungen 1-7 vermessen und die ABCD-Spektren der Protonen der Benzolringe berechnet. In Abhängigkeit vom Heteroatom in 1-Stellung wurde für die τ-Werte der chemischen Verschiebungen der 2-Methylprotonen folgende Abstufung gefunden: \documentclass{article}\pagestyle{empty}\begin{document}$$ - {\rm NR} - 〉 - {\rm CH = CH} - 〉 - {\rm O} - 〉 - {\rm S} - 〉 - {\rm Se} -. $$\end{document}Durch H/D-Austausch konnte gezeigt werden, daß sich die CH-Acidität der 2-Methylgruppe in der gleichen Reihenfolge ändert und mit kleiner werdenden τ-Werten ansteigt. Quantenchemische Rechnungen mit Hilfe der HMO- Methode bestätigten diese Aciditätsänderungen.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19733150404
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  • 6
    Electronic Resource
    Electronic Resource
    Organic polymers with indirect magnetic interaction caused by the symmetry of the elementary unitsDedicated to Professor Ronald Hoffmann on the occasion of his 60th birthday. (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 66 (1998), S. 425-434 
    Details
    ISSN: 0020-7608
    Keywords: polymers ; indirect magnetic interaction ; symmetry ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The magnetic properties of a class of 1-D π-systems having a frontier half-filled band of degenerate MOs localized within the elementary units (EU) were studied theoretically. The localization of the MOs is caused by the symmetry of the π-fragments which form the EUs. The localization and non-overlapping of the MOs results in vanishing of the direct (Hund) and the kinetic exchange interaction between the unpaired electrons. The indirect exchange of the unpaired electrons (spin-polarization exchange) occurs via the delocalized π-electrons in the filled energy bands. An approach allowing the calculation of the indirect exchange interaction is applied for a class of polymers having pyrene, azulene, and s-indacene as fragments of the EUs.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66: 425-434, 1998
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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