Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan).
Chemistry. 2013 Sep 23;19(39):12982-90. doi: 10.1002/chem.201302596. Epub 2013 Sep 9.
Polyoxometalates (POMs) with heterodinuclear lanthanoid cores, TBA8H4[{Ln(μ2-OH)2Ln'}(γ-SiW10O36)2] (LnLn'; Ln = Gd, Dy; Ln' = Eu, Yb, Lu; TBA = tetra-n-butylammonium), were successfully synthesized through the stepwise incorporation of two types of lanthanoid cations into the vacant sites of lacunary γ-SiW10O36 units without the use of templating cations. The incorporation of a Ln(3+) ion into the vacant site between two γ-SiW10O36 units afforded mononuclear Ln(3+)-containing sandwich-type POMs with vacant sites (Ln1; TBA8H5[{Ln(H2O)4}(γ-SiW10O36)2]; Ln = Dy, Gd, La). The vacant sites in Ln1 were surrounded by coordinating W-O and Ln-O oxygen atoms. On the addition of one equivalent of [Ln'(acac)3] to solutions of Dy1 or Gd1 in 1,2-dichloroethane (DCE), heterodinuclear lanthanoid cores with bis(μ2-OH) bridging ligands, Dy(μ2-OH)2Ln', were selectively synthesized (LnLn'; Ln = Dy, Gd; Ln' = Eu, Yb, Lu). On the other hand, La1, which contained the largest lanthanoid cation, could not accommodate a second Ln'(3+) ion. DyLn' showed single-molecule magnet behavior and their energy barriers for magnetization reversal (ΔE/kB) could be manipulated by adjusting the coordination geometry and anisotropy of the Dy(3+) ion by tuning the adjacent Ln'(3+) ion in the heterodinuclear Dy(μ2-OH)2Ln' cores. The energy barriers increased in the order: DyLu (ΔE/kB = 48 K) < DyYb (53 K) < DyDy (66 K) < DyEu (73 K), with an increase in the ionic radii of Ln'(3+); DyEu showed the highest energy barrier.
具有异双核镧系元素内核的多金属氧酸盐 (POM)，TBA8H4[{Ln(μ2-OH)2Ln'}(γ-SiW10O36)2]（LnLn'；Ln = Gd，Dy；Ln' = Eu，Yb，Lu；TBA = 四丁基铵），通过将两种类型的镧系元素阳离子逐步掺入到缺位的γ-SiW10O36单元的空位中，成功合成，而无需使用模板阳离子。Ln(3+)离子掺入两个γ-SiW10O36单元之间的空位中，得到了具有空位的单核 Ln(3+)含夹心型 POM（Ln1；TBA8H5[{Ln(H2O)4}(γ-SiW10O36)2]；Ln = Dy，Gd，La）。Ln1 中的空位被配位的 W-O 和 Ln-O 氧原子包围。在 1,2-二氯乙烷（DCE）溶液中加入 Dy1 或 Gd1 中一个当量的[Ln'(acac)3]，选择性地合成了具有双(μ2-OH)桥联配体的异双核镧系元素核Dy(μ2-OH)2Ln'（LnLn'；Ln = Dy，Gd；Ln' = Eu，Yb，Lu）。另一方面，含有最大镧系元素阳离子的 La1 不能容纳第二个 Ln'(3+)离子。DyLn' 表现出单分子磁体行为，通过调整 Dy(3+)离子的配位几何形状和各向异性，可以通过调节异双核Dy(μ2-OH)2Ln'核中相邻的 Ln'(3+)离子来操纵其磁化反转的能垒（ΔE/kB）。能垒的增加顺序为：DyLu（ΔE/kB = 48 K）< DyYb（53 K）< DyDy（66 K）< DyEu（73 K），随着 Ln'(3+)离子的离子半径增加；DyEu 表现出最高的能垒。
