Sun Wen-Bin, Yan Peng-Fei, Jiang Shang-Da, Wang Bing-Wu, Zhang Yi-Quan, Li Hong-Feng, Chen Peng, Wang Zhe-Ming, Gao Song
Beijing National Laboratory of Molecular Science , State Key Laboratory of Rare Earth Materials Chemistry and Applications , College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , P. R. China . Email:
Key Laboratory of Functional Inorganic Material Chemistry , Ministry of Education , Heilongjiang University , Harbin 150080 , P. R. China.
Chem Sci. 2016 Jan 1;7(1):684-691. doi: 10.1039/c5sc02986d. Epub 2015 Oct 9.
A series of mononuclear lanthanide Zn-Dy-Zn type single-molecule magnets (SMMs) were synthesized and magnetically characterized. The four molecules ([Zn(L)DyCl]·2HO (), [Zn(L)Dy(MeOH)Br]·3HO (), [Zn(L)Dy(HO)Br]·[ZnBr] () and [Zn(L)DyCl]·2HO ()) 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. 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.
合成了一系列单核镧系元素锌-镝-锌型单分子磁体（SMMs）并对其进行了磁性表征。这四个分子（[Zn(L)DyCl]·2HO ()、[Zn(L)Dy(MeOH)Br]·3HO ()、[Zn(L)Dy(HO)Br]·[ZnBr] () 和 [Zn(L)DyCl]·2HO ()）尽管中心Dy(iii)离子的局部几何对称性较低，但均表现出具有相对较高能垒和磁滞温度的显著磁弛豫行为。研究表明，Dy(iii)离子周围电荷分布的对称性是决定SMMs弛豫的关键因素。这四个配合物将其磁易轴沿第一配位球的负电荷密集方向取向。因此，整个分子磁各向异性由由五个配位原子组成的硬平面（垂直于易轴）中的单个取代原子控制，并且该硬平面上较低的电荷分布与五个配位原子的近共面性相结合最终导致显著的磁慢弛豫。这为改善通常在镧系(iii)中心周围具有低局部几何对称性的单核镧系元素SMMs的动态磁弛豫提供了一种有效且合理的方法。
