Hydrothermal Syntheses, Crystal Structures, and Magnetic Properties of a Series of Unique Three-Dimensional Lanthanide鈭扥rganic Coordination Frameworks with a N-Protonated 2,6-Dihydroxypyridine-

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• 作者：Shao-Ming Fang ; E. Carolina San虄udo ; Min Hu ; Qiang Zhang ; Song-Tao Ma ; Li-Ran Jia ; Cong Wang ; Jia-You Tang ; Miao Du ; Chun-Sen Liu
• 刊名：Crystal Growth & Design
• 出版年：2011
• 出版时间：March 2, 2011
• 年：2011
• 卷：11
• 期：3
• 页码：811-819
• 全文大小：1042K
• 年卷期：v.11,no.3(March 2, 2011)
• ISSN：1528-7505

文摘

A series of novel three-dimensional (3-D) lanthanide鈭抩rganic frameworks (LnOFs), with the general formula [Ln₂(H-L)₃(H₂O)₄]_{鈭?/sub> (Ln = Dy^III for 1, Gd^III for 2, Tb^III for 3, Eu^III for 4, and Ho^III for 5; H-L = N-protonated 2,6-dihydroxypyridine-4-carboxylate), have been synthesized under hydrothermal conditions. X-ray structural analysis reveals that complexes 1鈭?b>5 are isostructural and show the unique 3-D coordination framework with a trinodal (3,4,5)-connected (4.6²)(4².6)(4².8⁴)(4³.6.8⁶)(4².6⁵.8³) net topology, in which the H-L ligands adopt different 渭4- and 渭3-bridging forms. Variable-temperature magnetic susceptibility studies reveal that complexes 1鈭?b>3 and 5 show ferromagnetic behaviors. Notably, complex 1 (Dy^III) is the first instance leading to ferromagnetic coupling for a lanthanide ion through a spin-polarization mechanism. The alternating current (ac) signal observed for 1 and 5 should originate from the long-range ferromagnetic ordering, or it could reflect the splitting of the J multiplet for Dy^III or Ho^III under a low symmetry crystal field, which would give rise to slow relaxation of the magnetization. Additionally, thermal stability of these crystalline materials has also been investigated by thermogravimetric analysis of mass loss.}