高配位3d过渡金属单离子磁体的构筑及磁构关系研究

Single molecule magnets are potentially useful in quantum computing, high density data storage and molecular spintronics. 3d transition-metal-based single-ion magnets have attracted intensive interest in the aspect of single molecule magnets because of their simple structure, easily exploring the magneto-structural relationship, and achieving higher barriers by tunable ligand field. The project focuses on the syntheses, structures, magnetic properties and the magneto-structural relationship of mononuclear 3d transition metal complexes with the high-coordinate geometry. Based on the axial-symmetrical foundation, we will design and synthesize the high-coordinate mononuclear 3d transition metal complexes with the large magnetic anisotropy by using the organic ligands with the axial symmetric coordination environment. The magnetic anisotropy of the resulting complexes will be investigated by the combination of HF-EPR spectroscopy and theoretical calculation. Afterwards, detailed magnetic measurement will be performed to characterize the behavior of single molecule magnet for the obtain complexes with large magnetic anisotropy. Finally, the relationship among the ligand field, the magnetic anisotropy and the behavior of single molecule magnet will be explored, and the 3d transition-metal-based single-ion magnets with the high-coordinate geometry and the high energy barrier will be constructed. The project will provide a new route and the important experimental for the syntheses of single molecule magnets with the higher Ueff.

单分子磁体在量子计算、高密度存储材料以及分子自旋电子学等领域具有广阔的应用前景。3d过渡金属单离子磁体具有结构简单易于研究磁构关系以及易于调控配体场获得高能垒等特点，因而成为近年来单分子磁体领域的研究热点。本项目以研究具有高配位构型的3d过渡金属单核配合物的制备、结构、磁性质、磁构关系等科学问题为主要内容。基于高配位构型的设计，利用能够导致具有轴对称性的配位环境的多齿有机配体，合成具有强磁各向异性的高配位3d过渡金属单核配合物，运用HF-EPR光谱和理论计算等方法表征其磁各向异性，通过磁测量对其详细表征单离子磁体性质，以此得到配体场-磁各向异性-单离子磁体的相关规律，最后利用这种规律争取构筑出高能垒的高配位3d过渡金属单离子磁体。本项目为设计合成高能垒的单分子磁体提供新的思路和重要的实验依据。

本项目以构筑特殊构型的单离子磁体和研究磁构关系为研究目的，基于过渡金属和稀土金属，设计合成了14个单离子磁体。基于高配位数，利用不同的抗衡离子和七齿配体pentapyridyldiamine首次构筑了一系列具有单冠三棱柱构型的Co(II)单离子磁体，研究了结构畸变不同对磁性质的影响。合成了两例同构的十配位的Dy(III)和Er(III)配合物，这种高配位的构型构成了球形的配体场，使得两种不同电子云密度分布的Dy(III)和Er(III)产生了磁各向异性，从而该两例配合物都表现出了慢磁弛豫行为。基于八面体构型，利用3-phenylpyrazole和4-methylpyridine配体构筑了两例具有易面磁各向异性的Co(II)单离子磁体；利用咪唑配体得到了两例具有相同配阳离子[Co(imidazole)6]2+的Co(II)单离子磁体，由于抗衡离子的不同导致它们的八面体配位构型的对称性发生变化，磁性测试表明有效翻转能垒值随着结构对称性下降而升高。利用3,4-二甲基吡啶构筑了兼具自旋交叉和单离子磁体性质的Co(II)配合物，为开发新型多功能分子材料提供了新的思路。