Zhang Haixia, Lin Shuang-Yan, Xue Shufang, Wang Chao, Tang Jinkui
State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, China.
Dalton Trans. 2014 Apr 28;43(16):6262-8. doi: 10.1039/c3dt53366b.
Five dinuclear lanthanide complexes with formula [Ln2L2(OAc)4(MeOH)a(H2O)b] · cMeOH · dH2O (a = 2, b = 0, c = 2, d = 0, Ln = Sm (1), Gd (2), Dy (3); a = 0, b = 2, c = 4, d = 2, Ln = Tm (4)) and [Yb2L2(OAc)4(MeOH)2]·[Yb2L2(OAc)4(H2O)2] · 2H2O (5) (HL = (E)-N'-(2-hydroxybenzylidene)-2-mercaptonicotinohydrazide), have been synthesized and their crystal structures and magnetic properties are reported. All five complexes are centrosymmetric, showing a similar dinuclear core with two lanthanide ions in each complex being bridged by acetate groups in the η(1):η(2):μ2 mode. The various coordination modes of acetate groups result in two kinds of coordination geometries for Ln ions with the ones in complexes 1-4 and the Yb2 in 5 being nine-coordinated with a mono-capped square antiprism geometry, while the Yb1 ions in the other part of complex 5 are eight-coordinated with a triangular dodecahedron geometry. Magnetic susceptibility studies reveal that complex 3 shows single molecule magnet behaviour with an energy barrier of 39.1 K. In addition, comparison of the structural parameters among the similar Dy2 SMMs with a η(1):η(2):μ2 coordination mode of carboxylate groups reveals the significant role played by coordination geometry in modulating the relaxation dynamics of SMMs.
已合成了五种分子式为[Ln₂L₂(OAc)₄(MeOH)ₐ(H₂O)ₓ]·cMeOH·dH₂O（a = 2，b = 0，c = 2，d = 0，Ln = Sm (1)、Gd (2)、Dy (3)；a = 0，b = 2，c = 4，d = 2，Ln = Tm (4)）以及[Yb₂L₂(OAc)₄(MeOH)₂]·[Yb₂L₂(OAc)₄(H₂O)₂]·2H₂O (5)（HL = (E)-N'-(2-羟基亚苄基)-2-巯基烟酰肼）的双核镧系配合物，并报道了它们的晶体结构和磁性。所有五种配合物均为中心对称，呈现出相似的双核核心，每个配合物中的两个镧系离子通过乙酸根以η(1):η(2):μ₂模式桥连。乙酸根的不同配位模式导致镧系离子有两种配位几何构型，配合物1 - 4中的镧系离子以及配合物5中的Yb₂为九配位，具有单帽四方反棱柱几何构型，而配合物5另一部分中的Yb₁离子为八配位，具有三角十二面体几何构型。磁化率研究表明配合物3表现出单分子磁体行为，能垒为39.1 K。此外，对具有η(1):η(2):μ₂羧酸根基团配位模式的类似Dy₂单分子磁体的结构参数进行比较，揭示了配位几何构型在调节单分子磁体弛豫动力学中所起的重要作用。
