高性能稀土单分子磁体和分子磁制冷剂的可控制备及性能调控

含7-13个4f电子的重稀土金属离子兼具大的自旋值和磁各向同性/各向异性于一体,是制备新一代高性能单分子磁体和低场大磁熵变分子磁制冷剂的理想原料。本项目的研究目标之一是通过选择和调节配体的对称性及空间位阻,来制备具有罕见D5h和D6d等对称性的稀土配合物，探索通过控制对称性来抑制量子隧穿效应,从而显著提高稀土基单分子磁体的自旋翻转能垒以及相应的可应用温度(即阻塞温度)。目标之二是利用大的自旋值以及磁各向同性Gd3+(4f7)离子与分子量小的多连接无机和有机桥连配体制备磁密度大的钆配合物，获得若干种具有显著磁热效应的低场大磁熵变分子磁制冷剂，进一步通过分子工程、晶体工程以及磁工程策略来调控其磁有序温度，制备出适合较宽温度范围(2-20K)的分子基磁制冷材料。

Heavy rare earth ions, 4f7-13, characteric of large spins, magnetic isotropy and anisotropy, have attracted extensively attention to prepare new generation of molecular magnetic materials, including single-molecular magnets (SMMs) and Magnetic Refrigerants, which have potential applications as expected new-generation high-density information storage and processing materials and magnetic refrigerators, respectively. One target of this project aims at preparing high-symmetry polynuclear or mononuclear lanthanide(III) complexes by judicious choice of ligand with high symmetry and/or stereo-hindrance effect to enhance the energy barrier and applicable temperature of SMMs. Another target aims at preparing different-dimensional (0-3D) highly-tunable molecular magnets by the isotropic 4f7 Gd3+ ions with versatile bridging ligands. The magnetocaloric effect parameter delta(S) will be extracted indirectly from M-H curves and also be determined from the heat capacity measurements. Strategies of molecular engineering, crystal engineering as well as magnetic engineering will be applied to develop high-performance molecular magnetic coolers by tuning the magnetic couplings and Tc temperatres.