Structure and properties of nonclassical polymers X. Heteroatomic polymers with degenerate half-filled band |
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Authors: | K Müllen M Baumgarten N Tyutyulkov F Dietz |
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Institution: | (1) Max-Planck Institut für Polymerforschung, Ackermannweg 10, D-55128 Mainz, Germany;(2) Fakultät für Chemie und Mineralogie der Universität Leipzig, D-04105 Leipzig, Germany;(3) Present address: Faculty of Chemistry, University of Sofia, J. Bourchier Bd. 1, BG-1126 Sofia, Bulgaria |
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Abstract: | It is shown that the group of -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 -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 -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.Part IX:Theoret. Chim. Acta
86, 353–367 (1993). |
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Keywords: | Narrow-band high-spin heteronuclear polymers nature of spin-exchange interaction |
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