Department of Chemistry, Zhengzhou University, Zhengzhou 450052, People's Republic of China.
Inorg Chem. 2010 Mar 15;49(6):2600-13. doi: 10.1021/ic901113p.
Five interesting metal-organic nanostructures and networks, Ni(4)(HL)(4)(bpy)(py)(H(2)O)(5) x 0.5 H(2)O (1), Co(4)(HL)(4)(bpy)(py)(H(2)O)(5) x 0.5 H(2)O (2), Ni(4)(HL)(4)(H(2)O)(7) x nH(2)O (3), Ni(4)(HL)(4)(bpy)(2)(H(2)O)(4) (4), and Cd(4)(HL)(4)(H(2)O) (5), were synthesized hydrothermally [H(3)L = 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 M(4)(HL)(4), where doubly deprotonated HL in the same bichelating fashion of mu-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 M(4)(HL)(4) and the linkage styles between metal nodes and HL in M(4)(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 C(1)-symmetric M(4)(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-S(4)- or S(4)-symmetric M(4)(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 C(2)-symmetric M(4)(HL)(4) that fabricates the alpha-Po net of 5. Notably, those large M(4)(HL)(4) units are potentially highly connected building blocks in a hierarchical assembly of metal-organic networks. Magnetic studies disclose antiferromagnetic interactions in M(4)(HL)(4) of 1-4. The magnetic data for 1, 3, and 4, all containing isomeric Ni(4)(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.
五个有趣的金属有机纳米结构和网络，Ni(4)(HL)(4)(bpy)(py)(H(2)O)(5) x 0.5 H(2)O (1)，Co(4)(HL)(4)(bpy)(py)(H(2)O)(5) x 0.5 H(2)O (2)，Ni(4)(HL)(4)(H(2)O)(7) x nH(2)O (3)，Ni(4)(HL)(4)(bpy)(2)(H(2)O)(4) (4)，和Cd(4)(HL)(4)(H(2)O) (5)，是通过水热法合成的[H(3)L = 2-(吡啶-2-基)-1H-咪唑-4,5-二羧酸，py = 吡啶，和 bpy = 4,4'-联吡啶]。有趣的是，所有的化合物都由新型金属大环[4]芳烃构建块 M(4)(HL)(4)组成，其中双去质子化的 HL 以 μ-KN，N':kO，N''的双螯合方式显示出通过 4,5-咪唑二羧酸和 2-吡啶基的协同作用的强配位取向。非常有趣的是，M(4)(HL)(4)的对称性和金属节点与 HL 之间的连接方式对反应条件敏感，所得结构基元随二级配体和金属节点而变化。在 1 和 2 中，两个 C(1)-对称的 M(4)(HL)(4)单元被 bpy 桥联成具有两个不同空腔的手性纳米分子。当与 NaOH 去质子化时，Ni(II)和 HL 的组合形成伪 S(4)-或 S(4)-对称的 M(4)(HL)(4)，进一步组装成 1D 手性晶体 3 或稀有的 3D 晶体 4，具有金属大环[4]芳烃构建块作为新型 4-连接节点的 5 倍互穿金刚石结构，而 Cd(II)和 HL 的组合形成具有 C(2)-对称的 8 连接的 M(4)(HL)(4)，构建了 5 的 alpha-Po 网络。值得注意的是，那些大的 M(4)(HL)(4)单元是金属-有机网络的分级组装中潜在的高连接构建块。磁性研究揭示了 1-4 中 M(4)(HL)(4)的反铁磁相互作用。对于含有异构 Ni(4)(HL)(4)单元的 1、3 和 4，所有的磁性数据都通过等边四边形各向同性模型结合分子场近似进行分析，得到 J = -4.00(2)、-3.39(2)和-2.72(3)cm(-1)，分别呈现出结构与磁性之间更强的比较。5 的发射是奇数的，这也许与配体 HL 的双螯合方式和 Cd(II)的罕见配位几何有关。此外，还测量了这些化合物的热稳定性和气体吸附性能。
