多酸构筑的单分子磁体

Polyoxometalate-mediated Single-molecule Magnets

设计合成具有单分子磁体行为的分子磁性材料近年来受到广泛关注.合成单分子磁体的一个常用策略是利用有机多齿含氧或含氮配体将各种自旋载体组装成簇,使之具有高基态自旋值(S)和负的单轴磁各向异性值(D),进而满足形成单分子磁体所需的磁能垒.令人感兴趣的是近年来多酸发展成为一类构筑新型单分子磁体的无机建筑基元.多酸是一类独特的具有富氧表面、可控的尺寸、形状和电荷的无机纳米级金属氧簇,同时,一系列缺位多酸衍生物能够结合各种过渡金属或稀土离子形成多核金属簇合物.近五年来,多酸已作为一类无机多齿含氧配体成功构筑系列具有单分子磁体行为的新型过渡金属簇合物、稀土簇合物和3d-4f杂金属簇合物.特别是一些缺位多酸配体能够为稀土离子提供完美的配体场,进而构筑新一代的单离子磁体.此外,高自旋、磁各向异性单元(如单分子磁体)还可被均匀分散在具有孔道特征的多酸三级结构中,形成具有单分子磁体行为的多酸基复合材料.最近,以多酸为模板构筑具有单分子磁体行为的多核簇合物也取得了新进展.本综述旨在对近五年来利用多酸构筑的单分子磁体化合物进行评论,重点阐述利用多酸设计合成单分子磁体的策略、多酸在单分子磁体化合物结构中的作用和优势,以及多酸构筑单分子磁体这一研究课题的发展前景.

The design and synthesis of molecular-based materials displaying single-molecule magnet （SMM） property is currently a subject of worldwide research activity. A common strategy is the use of organic multi-dentate O-donor and/or N-donor ligands to assemble various spin carriers into simple complexes or polynuclear clusters so as to satisfy the essential necessaries of a SMM combing with large spin （S） and negative uniaxial anisotropy （D）. It is interesting that polyoxonieta- lates （POMs） have recently been developed as a new type of inorganic building blocks for the preparation of SMMs. Gener- ally, POMs are one type of unique inorganic nanoscale clusters with oxygen-rich surfaces, controllable size, shape and charge as well as a series of lacunary structural species, which tend to combine various transition metal （TM） and/or lanthanide （Ln） ions into giant clusters or aggregates. In last five years, a number of {TM,}-, {Lnn}-, and {TMxLnv}-based SMMs by the use of POM ligands were reported. Especially, some POMs can also provide an ideal ligand field for Ln ions so as to obtain new type of single-ion magnets （SIMs）, which has marked a new impetus in this area. Furthermore, the hybrid POM materials behaving as SMMs have been prepared by dispersing high-spin anisotropic units （like SMMs） into the porous anionic POM-based structures. A recent advance has also focused on the construction of POM-templated polynuclear clusters with SMM properties. In this review, we will give an overall perspective of the present POM-mediated SMMs with the emphasis on the synthetic strategies, the roles and advantages of POMs in the preparation of SMMs as well as the new prospect of this research field in the near future.