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  • 1
    ISSN: 1572-8951
    Keywords: Narrow-band high-spin heteronuclear polymers ; nature of spin-exchange interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is shown that the group of π-conjugated, nonclassical (non-Kekulé) homonuclear, alternative organic polyradicals and polymers with degenerate NBMOs can be essentially extended to a large class of heterocyclic analogues having a set of degenerate MOs. The presence of a set of degenerate MOs (DMOs) results from the molecular topology of the system. The conditions of occurrence of DMOs are determined by the generalized Coulson-Rushbrooke-Longuet-Higgins theorem. The character of spin-exchange interaction of π-electrons in the half-filled band (HFB) of a large group of model polymers, analogues of poly(meta-anilines), has been investigated. It is shown that the main component of the ferromagnetic exchange interaction is the potential (Coulomb) exchange and a smaller contribution of the indirect exchange among the HFB electrons via the delocalized π-electrons in the occupied bands. The theoretical method used, which predicts the existence of a set of DMOs, may serve as a guiding principle in the design of narrow-band, high-spin organic polymers in which cooperative magnetic phenomena can arise.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 200 (1964), S. 54-56 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary A distillation procedure is described for the separation of simple cyanides and of complex cyanides of zinc, cadmium, nickel, and copper from hexacyanoferrates and thiocyanates. Hexacyanoferrates are converted to slightly soluble compounds by use of zinc acetate. Complexes of copper(I) are converted to those of copper(II) by potassium dickromate, as copper(II) complexes are decomposable more easily. The distillation is performed at pH 5.2–5.5. The procedure is applicable to concentrations up to 25 mg CN/ml. It can be used for checking the detoxification of cyanide containing waste water by chlorine or active chlorine compounds.
    Notes: Zusammenfassung Es wird ein Destillationsverfahren beschrieben, das die Trennung der einfachen Cyanide some des an Zink, Cadmium, Nickel oder Kupfer komplex gebundenen Cyanids von Hexacyanoferraten und Thiocyanat gestattet. Durch Zinkacetat werden die Hexacyanoferrate in schwerlösliche Verbindungen überführt. Kupfer(I)-komplexe werden durch Kaliumdichromat in Kupfer(II)-Verbindungen übergeführt, die leichter zersetzbar sind. Die Destillation erfolgt bei pH 5,2–5,5. Das Verfahren ist für Konzentrationen bis 25 mg CN/l anwendbar. Es kann zur Beurteilung der Entgiftung cyanidhaltiger Abwässer mit Chlor bzw. aktiven Chlorverbindungen benutzt werden.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 167-169 
    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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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 990-990 
    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
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  • 5
    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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