Hierarchical Assembly of Extended Coordination Networks Constructed by Novel Metallacalix[4]arenes Building Blocks

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• 作者：Xia Li ; Benlai Wu ; Ruiying Wang ; Hongyun Zhang ; Caoyuan Niu ; Yunyin Niu ; Hongwei Hou
• 刊名：Inorganic Chemistry
• 出版年：2010
• 出版时间：March 15, 2010
• 年：2010
• 卷：49
• 期：6
• 页码：2600-2613
• 全文大小：1706K
• 年卷期：v.49,no.6(March 15, 2010)
• ISSN：1520-510X

文摘

Five interesting metal−organic nanostructures and networks, [Ni₄(HL)₄(bpy)(py)(H₂O)₅]₂·0.5H₂O (1), [Co₄(HL)₄(bpy)(py)(H₂O)₅]₂·0.5H₂O (2), [Ni₄(HL)₄(H₂O)₇]_n·nH₂O (3), [Ni₄(HL)₄(bpy)₂(H₂O)₄]_n (4), and [Cd₄(HL)₄(H₂O)]_n (5), were synthesized hydrothermally [H₃L = 2-(pyridin-2-yl)-1H-imidazole-4,5-dicarboxylate acid, py = pyridine, and bpy = 4,4′-bipyridine]. Intriguingly, all compounds consist of novel metallacalix[4]arene building blocks M₄(HL)₄, where doubly deprotonated HL in the same bichelating fashion of μ-kN,N′:kO,N′′ displays a strong coordination orientation by cooperation of the 4,5-imidazoledicarboxylate and 2-pyridyl groups. Very interestingly, the symmetry of M₄(HL)₄ and the linkage styles between metal nodes and HL in M₄(HL)₄ are sensitive to the reaction conditions, and the resulting structural motifs vary with secondary ligands and metal nodes. In 1 and 2, two C₁-symmetric M₄(HL)₄ units are bpy-bridged into dimeric chiral nanomolecules with two different cavities. As deprotonated with NaOH, the combination of Ni^II and HL forms a pseudo-S₄- or S₄-symmetric M₄(HL)₄, which further assembles into 1D chiral crystals 3 or rare 3D crystals 4 of bpy-bridged 5-fold interpenetrating diamondoid architecture with metallacalix[4]arene building blocks as novel 4-connecting nodes, and the combination of Cd^II and HL forms an 8-connected C₂-symmetric M₄(HL)₄ that fabricates the α-Po net of 5. Notably, those large M₄(HL)₄ units are potentially highly connected building blocks in a hierarchical assembly of metal−organic networks. Magnetic studies disclose antiferromagnetic interactions in M₄(HL)₄ of 1−4. The magnetic data for 1, 3, and 4, all containing isomeric Ni₄(HL)₄ units, are analyzed by an equilateral quadrangle isotropic model combined with the molecular-field approximation with J = −4.00(2), −3.39(2), and −2.72(3) cm⁻¹, respectively, presenting a stronger comparison between the structure and magnetism. The emission of 5 is odd, which perhaps is relative to the bichelating fashion of ligand HL and a rare coordination geometry of Cd^II. Moreover, the thermal stability and gas sorption properties of these compounds were measured.