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 π-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 π-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 π-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 π-electron system, while localized d-spins in metallic complexes are coupled to each other via the π–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.