| The quest for new magnetic materials is a problem for synthetic chemists, whether the aim is to construct a specific discrete molecular cluster, or to form a desirable extended network topology. The synthetic construction of coordination polymers (a rapidly expanding field itself) have been recently reviewed, but it is worth to note that even the control of the strength of coupling interactions is challenging, especially if one aims for a strong magnetic interaction, since it not only relies upon the net work of ions linked by superexchange interactions, but the relative orientation of bridging ligand and magnetic(metalbased) orbitals is imperative. In addition anisotropy effects can be equally important in determining the magnetic behaviour of the system. In this respect it is clear that synthetically we have far to go be fore we are really making designer magnets.Single-Molecule Magnets (SMMs) are molecules with a high-spin ground state and uniaxial anisotropy which lead to slow relaxation of their magnetization. Therefore, they can act as monodisperse superparamagnetic particles for high-density magnetic data storage at the molecular level. The organization of SMMs or high-spin complexes into supramolecular or coordination networks becomes an appealing new goal for chemists to combine the intrinsic magnetic properties of such unique building-blocks and the inter-complex magnetic interaction in order to stabilize new magnetic behaviors.Polymetallic complexes of paramagnetic transition metals possessing large spin ground states are of interest since they can display either single-molecule magnetism behavior or an enhanced magnetocaloric effect (MCE). The latter describes the change of magnetic entropy (ΔS) following a change of the applied magnetic field (ΔH) and has potential technological use in cooling applications. Although the MCE is intrinsic to any magnetic material, in only a few cases is theΔS sufficiently large to make the materials suitable for applications. The key is to find the best performing refrigerant.Chiral Complexes in the magnetic materials, nonlinear optical materials and asymmetric catalysis has potential value, design and synthesis chiral magnet materials combining conversion function have attracted great interest of researchers.Chapter two, ST=22 [Mn10] Supertetrahedral Building-block to Design Extended Magnetic Networks is described, because of the Jahn-Teller effect of MnⅢ, which possesses much more single electron and uniaxial anisotropy, it can act as an important material of Mn synthetic chemistry. Herein, we present a series of materials based on the supertetrahedron [Mn10] motif using (i) 1,3-propanediol derivatives as chelating ligands to form the [Mn10] core unit and (ii) azide anions as linkers to synthesize the first three-dimensional [Mn10] networks. Magnetic measurements indicate that all the Mn ferromagnetically couples, the inter-complex of 3D-Mn indicate antiferromagnetically couples.Recently, molecular materials which possesses chiral and magnetic properties have interested more and more attention. We described the synthesis, structure and magnetic properties of compound 3,3D-Mn(R).Chapter three desbribe three 3d-4f heterometallic clusters, compound 5-7. Magnetic mesurement indicate the domain interaction between Mn and Ln is ferromagnetically couples.Chapter four explores the basic principles of magnetic refrigeration, and the selection of magnetic materials, furthermore, researches the MCE by choosing suitable clusters.
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