ENERGY-SPECTRA AND MAGNETIC-PROPERTIES OF RADIALENES, DENDRALENES ANDTHEIR POLY-RADICAL IONS - A NEW CLASS OF POLARONIC HIGH-SPIN PI-SYSTEMS

The energy spectra of infinite radialenes (RA) and dendralenes (DE) - the simplest one-dimensional pi-systems possessing non-degenerate grou nd states - are theoretically investigated. Three factors, a topologic al, a geometrical, and a correlational, contribute to the energy gap o f 3.6 eV. The charge density distribution of the Jahn-Teller active mo no-cation of the [3]RA and the charged [6]RA, and the charged [6]DE is studied. The polymers derived from the poly-radical ions of infinite RAs possess a narrow half-filled band (HFB) within the energy gap. The different contributions to the effective spin exchange interaction be tween the unpaired electrons in the HFB: the potential exchange, the k inetic exchange, and the indirect exchange (due to the spin polarizati on) were calculated. In all cases the effective spin exchange is posit ive, i.e. the ground state of the polymers is a high-spin one. The fer romagnetic interaction within the HFB is due to the predominant role o f the direct Coulomb exchange. A juxtaposition between the structural principle of the polaronic high-spin systems considered here and Fukut ome's polaronic high-spin systems is discussed.