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

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.

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。

本项目紧密围绕高性能稀土单分子磁体和磁制冷材料开展研究，采用常规化学合成方法与溶剂热合成方法成功合成近60种目标产物，从结构基元和磁功能调控入手，成功探索出系列结构新奇的稀土单分子磁体组装方法，为单分子磁体的理论研究提供了重要实例；从高性能单离子磁体结构基元出发组装出混合d-f金属单分子磁体{Fe2Dy}和{Co2Dy}，其自旋翻转能垒分别达到459K和600K，将d-f单分子磁体的能垒纪录提高了3倍；通过优化D5h对称性单离子磁体的轴向及五角平面的配位场，创造了能垒超过1000K以及TB温度达20K的新纪录；提出“桥连间隔d-f金属”等组装新方法，设计并制备出氟化钆和羟基乙酸锰等系列磁热效应显著的超低温磁制冷材料。.基于上述研究共发表SCI收录论文31篇，其中包括2篇J. Am. Chem. Soc.，2篇Angew. Chem. Int. Ed.，2篇Coord. Chem. Rev.，3篇J. Mater. Chem. A/C，4篇Chem. Eur. J.，6篇Inorg. Chem.。4篇入选ESI高被引论文，2篇入选ESI热点论文。授权发明专利3件。在国际重要学术会议作主题和邀请报告12次，在国内重要学术会议作主题和邀请报告13次。本项目高质量地实现了原计划的科学研究目标。