Design and Preparation of an Organic Magnetic Metal using Novel pi-Electron System

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Development of organic magnetic metals is one of the most interest investigation for molecular magnetism. In such spin system, it is required a spin correlation between conduction electrons and local spins. We designed a series of open shell donors which are candidate molecules as components of such spin system. The open shell donors are constructed with a donor and a radical unit and they are connected so as to become a cross-conjugate pi-system when one-electron oxidation takes place. Cationdiradicals of the open-shell donors were generated in THF solution by treating with iodine. ESR spectra measurement of them indicated the cationdiradicals are all ground state triplet species. Molecular orbital calculation appeared an unique electronic structure of them to us as follows : They have two orthogonal singly occupied molecular orbitals (SOMOs) with different orbital energies. While coefficients of one SOMO of them distribute over the whole molecule, that of the other one localize only on the radical unit. It is considered that large positive exchange interaction arises at the site hold the coefficients of two SOMOs. We prepared also an open-shell donor composed of two nitronyl nitroxides as the radical unit and tetraphenylphenylenediamine as the donor unit. The ESR study showed that they changed the ground state multiplicity from singlet to quartet through one-electron oxidation. These results indicate that these open-shell donors satisfy one of the required conditions for the components of organic magnetic metals.