Evolution from a single relaxation process to two-step relaxation processes of Dy2 single-molecule magnets via the modulations of the terminal solvent ligands
Evolution from a single relaxation process to two-step relaxation processes of Dy2 single-molecule magnets via the modulations of the terminal solvent ligands
复制标题
通过末端溶剂配体的调节，Dy(2) 单分子磁体从单一弛豫过程演变为两步弛豫过程。
DOI：
10.1039/d0dt03093g
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发表时间：
2021-01-07
影响因子：
4
通讯作者：
Yao，Jinlei
中科院分区：
文献类型：
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作者：
Li，Dawei;Ding，Man-Man;Yao，Jinlei
为了探索磁相互作用对单分子磁体弛豫动力学的影响，了解单离子弛豫与分子实体弛豫的关系，设计具有两步弛豫过程的双核镧系磁体是非常重要的。通过引入不同的末端溶剂配体，成功地合成了三个Dy2配合物[Dy2(L)2(NO3)2(MeOH)2](1)，[Dy2(L)2(NO3)2(Etoh)2](2)和[Dy2(L)2(NO3)2(DMF)2]·0.5EtOH(3)(H2L=2-(((2-hydroxy-3-methoxybenzyl)imino)methyl)-4-methoxyphenol))。X-射线单晶衍射分析表明，化合物1-3是等结构的。1和2的两个DyIII离子都具有D2D对称性，而3的两个DyIII中心分别具有D2D和D4D对称性。对化合物1-3的磁性研究表明，3种化合物均表现为单分子磁体(SMM)行为，在零直流场下，1的势垒为104K，2的势垒为98.94 K，3的势垒为76.28 K和45.54 K。通过逐渐增大末端溶剂配体的尺寸，实现了两步松弛组装Dy2 SMM的目标。配合物3表现出两步弛豫过程。在1-3上进行了完整的活动空间自洽场(CASSCF)计算，以合理地解释观测到的磁行为的差异。研究发现，磁轴与连接DyIII离子的矢量之间的夹角θ和DyIII离子的对称性都是影响1-3势垒的重要因素。中心金属1和2的高局域对称性使其成为具有较高势垒的SMM，而较小的θ角和两个DyIII离子的不同对称性使配合物3成为具有两步弛豫过程的SMM。这项工作展示了一种通过微调末端溶剂配体来制备具有两步松弛过程的SMM的新方法。
To explore the influences of magnetic interactions on the relaxation dynamics of single-molecule magnets (SMMs) and to understand the relationship between single-ion relaxation and the relaxation of a molecular entity, it is very important to design dinuclear lanthanide-based SMMs with two-step relaxation processes. Here, three Dy2 complexes of compositions [Dy2(L)2(NO3)2(MeOH)2] (1), [Dy2(L)2(NO3)2(EtOH)2] (2), and [Dy2(L)2(NO3)2(DMF)2]·0.5EtOH (3) (H2L = 2-(((2-hydroxy-3-methoxybenzyl)imino)methyl)-4-methoxyphenol) were successfully synthesized via elaborately introducing different terminal solvent ligands. X-ray single-crystal diffraction analyses revealed that complexes 1–3 are isostructural. The two DyIII ions of 1 and 2 both adopt D2d symmetry, while the two DyIII centres of 3 display D2d and D4d symmetries, respectively. The magnetic property studies of 1–3 indicated that all three complexes exhibit single-molecule magnet (SMM) behaviours with energy barriers of 104 K for 1, 98.94 K for 2, and 76.28 K and 45.54 K for 3 under zero dc field. The target of assembling Dy2 SMMs with two-step relaxation processes was achieved by gradually increasing the sizes of the terminal solvent ligands. Complex 3 exhibits two-step relaxation processes. Complete active space self-consistent field (CASSCF) calculations were performed on 1–3 to rationalize the observed differences in the magnetic behaviour. It is found that both the angles θ between the magnetic axis and the vector connecting two DyIII ions and the symmetries of DyIII ions are vital factors that affect the energy barriers of 1–3. The high local symmetries of the central metals in 1 and 2 make the complexes act as SMMs with higher energy barriers, while the smaller θ angle and different symmetries of the two DyIII ions render complex 3 as a SMM with a two-step relaxation process. This work demonstrates a new methodology for preparing SMMs with two-step relaxation processes by fine-tuning the terminal solvent ligands.