Molecular Designs for Polyionic Organic Ferromagnetics in Terms of Band Structure Calculation/ Crystal Orbital Approach; Exploitation of Topological Super Pseudo-Degeneracy of π-Bco's and π-Abco's with Hetero-Atomic Perturbation

Abstract

One of the highlighted conceptual advances in organic magnetics and molecule-based magnetism has been that the use of topological-symmetry requirement in the π-electron network of “open-shell homoatomic neutral hydrocarbon systems” gives rise to the unlimited number of the degeneracy in non-bonding molecular orbitals (coined as topological degeneracy). This paper deals with the π-topological version of an approach to purely organic polyionic polymer ferromagnets, emphasizing that molecular design exploits the topological super pseudo-degeneracy of π-bonding and π-antibonding crystal orbitals (π-BCOs and π-ABCOs; it-bands) appearing close to zero energy in heteroatomic π-conjugated organic systems, for polycationic and polyanionic organic polymer ferromagnets, respectively. The appearance of the BCOs and ABCOs close to zero energy as well as their pseudo-degeneracy is due to heteroatomic perturbation. Their super degeneracy arises from the topological nature of the π-conjugated electron network of the elaborate molecular design. Oxidation and reduction states of polymers designed according to the topological approach are expected to undergo the additive operation of dynamic spin polarization, leading to high-spin ground states for polycationic and polyanionic model polymers, respectively. One-dimensional and two-dimensional star-burst model oligomers with heteroatoms in π-conjugation were designed as prototypical examples. Also, description of ferromagnetic or antiferromagnetic spin alignment depending on the topological symmetry in π-conjugation is given in terms of dynamic spin polarization.