MOLECULAR DESIGNS FOR POLYIONIC ORGANIC FERROMAGNETICS IN TERMS OF BAND-STRUCTURE CALCULATION CRYSTAL ORBITAL APPROACH - EXPLOITATION OF TOPOLOGICAL SUPER PSEUDO-DEGENERACY OF PI-BCOS AND PI-ABCOS WITH HETERO-ATOMIC PERTURBATION

One of the highlighted conceptual advances in organic magnetics and mo lecule-based magnetism has been that the use of topological-symmetry r equirement in the pi-electron network of ''open-shell homoatomic neutr al hydrocarbon systems'' gives rise to the unlimited number of the deg eneracy in non-bonding molecular orbitals (coined as topological degen eracy). This paper deals with the pi-topological version of an approac h to purely organic polyionic polymer ferromagnets, emphasizing that m olecular design exploits the topological super pseudo-degeneracy of pi -bonding and pi-antibonding crystal orbitals (pi-BCOs and pi-ABCOs; pi -bands) appearing close to zero energy in heteroatomic pi-conjugated o rganic systems, for polycationic and polyanionic organic polymer ferro magnets, respectively. The appearance of the BCOs and ABCOs close to z ero energy as well as their pseudo-degeneracy is due to heteroatomic p erturbation. Their super degeneracy arises from the topological nature of the pi-conjugated electron network of the elaborate molecular desi gn. Oxidation and reduction states of polymers designed according to t he 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-dimensi onal and two-dimensional star-burst model oligomers with heteroatoms i n pi-conjugation were designed as prototypical examples. Also, descrip tion of ferromagnetic or antiferromagnetic spin alignment depending on the topological symmetry in pi-conjugation is given in terms of dynam ic spin polarization.