High symmetry or low symmetry, that is the question - high performance Dy(iii) single-ion magnets by electrostatic potential design.
High symmetry or low symmetry, that is the question - high performance Dy(iii) single-ion magnets by electrostatic potential design.
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高对称性还是低对称性，这是个问题——静电势设计的高性能Dy(III)单离子磁体
DOI：
10.1039/c5sc02986d
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发表时间：
2016-01-01
期刊：
影响因子：
8.4
通讯作者：
Gao S
中科院分区：
文献类型：
--
作者：
Sun WB;Yan PF;Jiang SD;Wang BW;Zhang YQ;Li HF;Chen P;Wang ZM;Gao S
合适的配基电荷排列可以弥补低对称性体系的不足，并诱导出出乎意料的SMM行为。合成了一系列单核稀土元素Zn-Dy-Zn型单分子磁体，并对其进行了磁学表征。这四个分子([Zn2(L1)2DyCl3]·2H2O(1)，[Zn2(L1)2DY(MeOH)Br3]·3H2O(2)，[Zn2(L1)2Dy(H2O)Br2]·[ZnBr4]0.5(3)和[Zn2(L2)2DyCl3]·2H2O(4))都表现出显著的磁弛豫行为，具有较高的能垒和磁滞温度，尽管具有较低的中心Dy(III)离子的局部几何对称性。从头算研究表明，Dy(III)离子周围电荷分布的对称性是决定SMM驰豫的关键因素。这四个络合物的磁易轴沿着第一配位球的负电荷密度方向定向。因此，整个分子的磁各向异性是由硬面上的一个取代基原子控制的，硬面上由五个配位原子(垂直于易轴)组成，较低的电荷分布和五个配位原子的近乎共面最终导致了显著的磁慢弛豫。这为改善通常在La3+中心附近具有较低局域几何对称性的单核稀土SMM的动态磁驰豫提供了一种有效而合理的方法。
A suitable arrangement of the ligand charge can complement a low symmetry system and induce an excellent unexpected SMM behavior. A series of mononuclear lanthanide Zn–Dy–Zn type single-molecule magnets (SMMs) were synthesized and magnetically characterized. The four molecules ([Zn2(L1)2DyCl3]·2H2O (1), [Zn2(L1)2Dy(MeOH)Br3]·3H2O (2), [Zn2(L1)2Dy(H2O)Br2]·[ZnBr4]0.5 (3) and [Zn2(L2)2DyCl3]·2H2O (4)) all display remarkable magnetic relaxation behavior with a relatively high energy barrier and hysteresis temperature, despite possessing a low local geometry symmetry of the center Dy(iii) ions. Ab initio studies revealed that the symmetry of the charge distribution around the Dy(iii) ion is the key factor to determine the relaxation of the SMMs. The four complexes orient their magnetic easy axes along the negative charge-dense direction of the first coordination sphere. The entire molecular magnetic anisotropy was therefore controlled by a single substituent atom in the hard plane which consists of five coordination atoms (perpendicular to the easy axis), and the lower charge distribution on this hard plane in combination with the nearly coplanarity of the five coordination atoms ultimately lead to the prominent magnetic slow relaxation. This offers an efficient and rational method to improve the dynamic magnetic relaxation of the mononuclear lanthanide SMMs that usually possess a low local geometry symmetry around the lanthanide(iii) center.
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