Molecular magnets based on organic charge transfer complexes

Organic charge transfer complexes form a large variety of electronic structures from insulating state to metallic state in low-dimensional frameworks, which are governed by the competition between the transfer integral and the on-site Coulomb interaction. In the insulating regime, the generation of localized magnetic moments of pi-electron origin provides low-dimensional magnetic systems having the features of quantum spins. The increase in the transfer integral which works to suppress the effect of on-site Coulomb interaction makes x-electrons delocalized, resulting in the appearance of the systems with the coexistence of magnetism and electron transport as materials classified around the Mott-Hubbard boundary. The introduction of localized magnetic moments of d-electrons in the complexes gives rise to the interaction between the cc-electrons and the magnetic moments of d-electrons. Localized magnetic moments of d-electrons embedded in insulating complexes are expected to interact with each other through superexchange interaction mediated by the organic ?c-electron system, while localized d-spins in metallic complexes are coupled to each other via the pi-d interaction, leading to the generation of molecule-based metal magnets. The studies of organic complex-based molecular magnets based on TTF-type donor molecules performed in our group are reviewed.