School of Textile Science and Engineering, Xi'an Polytechnic University, Xi'an, 710048, P.R. China.
Dalton Trans. 2019 Feb 5;48(6):2135-2141. doi: 10.1039/c8dt05004j.
The study of mononuclear lanthanide-based systems, where the observed Single Molecule Magnets (SMMs) properties originate from the local magnetic anisotropy of the single lanthanide ion, has been extensively investigated in the literature. The case for polynuclear lanthanide SMMs becomes more challenging both experimentally and theoretically due to the complexity of such architectures involving interactions between the magnetic centers. Much interest was devoted to the study of the structural effect on the magnetic interactions and relaxation dynamics. However, the understanding of the structural influence on those two factors remains a difficult task. To address this issue, a system containing two structurally related tetranuclear Dy(iii) SMMs, namely [Dy4(L)4(OH)2(DMF)4(NO3)2]·2(DMF)·(H2O) (1) and [Dy4(L)4(OH)2(DMF)2(NO3)2] (2) (H2L = 2-(2-hydroxy-3-methoxybenzylideneamino)phenol), is introduced and investigated. Through modifying the ligands on the changeable coordination sites, the intramolecular magnetic interactions and relaxation dynamics in these two Dy(iii)4 SMMs can be tuned. Both complexes exhibit slow relaxation of their magnetization with a relaxation barrier of 114 K for complex 2 while a blocking temperature below 2 K is observed for complex 1. Ab initio calculations reveal that changes in coordination numbers and geometries on the Dy(iii) sites can significantly affect the magnetic interactions as well as single-ion anisotropy. The combination of experimental work and ab initio calculations offers insight into the relationship between structures and magnetic properties and sheds light on the rational design of future polynuclear lanthanide SMMs with enhanced magnetic properties.
单核镧系元素基体系的研究，其中观察到的单分子磁体（SMMs）性质源自单个镧系离子的局部磁各向异性，在文献中得到了广泛研究。由于涉及磁心之间相互作用的这种结构的复杂性，多核镧系元素 SMMs 的情况在实验和理论上都变得更加具有挑战性。人们对结构对磁相互作用和弛豫动力学的影响进行了大量研究。然而，对结构对这两个因素的影响的理解仍然是一个难题。为了解决这个问题，引入并研究了包含两个结构相关的四核 Dy(iii) SMM 的系统，即[Dy4(L)4(OH)2(DMF)4(NO3)2]·2(DMF)·(H2O)（1）和[Dy4(L)4(OH)2(DMF)2(NO3)2]（2）（H2L = 2-(2-羟基-3-甲氧基苯亚甲基氨基)苯酚）。通过改变可交换配体在这些两个 Dy(iii)4 SMM 中的内分子磁相互作用和弛豫动力学。这两个配合物都表现出磁化的缓慢弛豫，对于配合物 2，弛豫势垒为 114 K，而对于配合物 1，观察到低于 2 K 的阻塞温度。从头算计算表明，Dy(iii)位点上的配位数和几何形状的变化可以显著影响磁相互作用以及单离子各向异性。实验工作和从头算计算的结合提供了对结构和磁性质之间关系的深入了解，并为具有增强磁性质的未来多核镧系元素 SMMs 的合理设计提供了启示。
