多齿胺配体构筑的镝配合物合成及磁性研究

Synthesis and magnetic properties of dysprosium complex Constructed by polydentate amine ligand

基于镧系离子基态电子云分布特点,选取强磁各向异性的镝离子为自旋中心,引入对硝基苯酚配体为强场配体,以2-吡啶甲醛和三(2-氨基乙基)胺为原料原位合成多齿胺弱场配体,制备一种九配位的单核镝配合物.单晶X-射线衍射研究发现,镝中心由大位阻的七齿胺配体螯合占位,其余配位点被强配体场酚氧阴离子占据并主导磁各向异性.交流磁化率研究发现,配合物在外加0.06 T磁场下展现了频率依赖的慢磁弛豫行为,有效能垒为20.1 cm-1;当继续增大外加磁场,表现为奇特的双弛豫过程.实验结果表明,多齿柔性氮配体可以作为一类弱供体选择,提供较弱的配体场环境和位阻以便强配体场主导磁各向异性.

The reasonable design of ligand field is the key to improve the magnetic properties of lanthanide single-molecule magnets.Based on the distribution characteristics of the ground state electron of lanthanide ions,a nine coordinated mononuclear dysprosium complex was prepared by selecting dysprosium ions with strong magnetic anisotropy as the spin center,introducing p-nitrophenol ligand as the strong field ligand and synthesizing weak field ligand in situ from 2-pyridine formaldehyde and tris(2-aminoethyl)amine.Single crystal X-ray diffraction studies show that the Dy3+center is occupied by chelating ligand with large steric hindrance,and the other sites are occupied by small phenolic oxygen molecules with strong ligand field and dominate the magnetic anisotropy.The study of AC susceptibility shows that the complex exhibits frequency dependent slow magnetic relaxation behavior with an effective energy barrier of 20.1 cm-1under a 0.06 T field.However,when the external magnetic field continues to increase,it presents a specific slow magnetic relaxation with two relaxation branches.The results show that flexible polydentate amines are explored as a kind of weak ligands for improving the magnetic anisotropy via control of transverse contributions as well as steric hindrance.