High-spin non-alternant polymers
Nature of spin exchange interaction
Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
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.
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