Development of Multi-functional Magnets Based on Supramolecular Architecture

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Supramolecular techniques have been used to tune molecule-based magnetic materials. We have developed nano-porous magnetic materials, whose magnetic properties were changed by inclusion of small diamagnetic molecules. Switchable magnets by means of host-guest chemistry have been investigated.Host-guest complexes of tri- and tetra-radical-substituted azamacrocycles afforded the folded structures of the hosts where the radical oxygen atoms were coordinated to the guest metal ion, leading to enhanced antiferromagnetic couplings in the solid state and an ESR line broadening in the solution phase.We also prepared metal-radical hybrid magnets using bridging ligands as supramolecular synthons. Novel paramagnetic chelating ligands (pzNN, pzIN, pzbisNN, pzbislN, 6bpyNO, and 2pyNO) were developed and applied to the synthesis of mono-, di-, tri-, and polynuclear complexes (NN, IN, and NO stand for organic free radical groups). We have exploited potential utility of the bridging paramagnetic ligands (HIN, HNN, CnPNN). A strong character of a single-chain magnet (SCM) is operative in the magnetically ordered state in the one-dimensional Co-C4PNN complex, giving a largest class of the coercive field (52 kOe (4.1 MA m^-1) at 6 K).Several oligonuclear 3d-4f heterometallic complexes have been characterized as ground ferrimagnetic high-spin molecules. Lanthanide ions are supposed to be promising candidates for the elements of single-molecule magnets (SMMs) because of the large magnetic momentum and anisotropy.We have established the [Dy_2Cu], [Dy_4Cu], and [Dy_2,Cu_2] complexes as new SMMs and [Dy_2,Cu_2,]_n, as a SCM. A plausible mechanism for quantum tunneling of magnetization has been proposed for the first time among the 3d-4f heterometallic SMMs and SCMs.