Novel Three-Dimensional Metal-Azide Network Induced by a Bipyridine-Based Zwitterionic Monocarboxylate Ligand: Structures and Magnetism

The 4,4′-bipyridine-based zwitterionic monocarboxylate ligand, 4,4′-dipyridinio-1-acetate (L), is used as coligand to construct novel magnetic coordination polymers with mixed azide and carboxylate bridges. Two compounds, [Co2(L)2(N3)4(H2O)]·4H2O (1) and [Mn6(L)4(N3)12(H2O)]·5H2O (2), have been structurally and magnetically characterized. Compound 1 consists of one-dimensional (1D) coordination chains in which the unprecedented binuclear motifs with mixed (μ-EO-N3)(μ-COO)2 (EO = end-on) triple bridges are cross-linked by the 4,4′-dipyridinium-N-methylene spacers. In compound 2, the azide anions link the metal ions into a very complicated three-dimensional (3D) network with unprecedented topology, and the zwitterionic coligand is embedded in and serves as additional supports for the 3D network. Magnetic studies reveal that the mixed (μ-EO-N3)(μ-COO)2 triple bridges transmit ferromagnetic coupling in the Co(II) compound, and the overall antiferromagnetic interactions exist in the Mn(II) compound.

以基于4,4'-联吡啶的两性离子单羧酸配体——4,4'-二吡啶鎓-1-乙酸盐（4,4′-dipyridinio-1-acetate，简称L）作为共配体，构建兼具叠氮桥与羧酸桥混合桥联结构的新型磁性配位聚合物。已合成两种化合物，分别为[Co₂(L)₂(N₃)₄(H₂O)]·4H₂O（1）与[Mn₆(L)₄(N₃)₁₂(H₂O)]·5H₂O（2），并对其进行了结构与磁性表征。化合物1呈现一维（1D）配位链结构，其中由前所未有的(μ-EO-N₃)(μ-COO)₂三重桥联的双核基元，通过4,4'-二吡啶鎓-N-亚甲基间隔基实现交联。在化合物2中，叠氮阴离子将金属离子桥联为具有前所未有的拓扑结构的复杂三维（3D）网络，两性离子共配体嵌入该网络并作为额外支撑结构。磁性研究结果表明，(μ-EO-N₃)(μ-COO)₂三重桥在Co(II)配合物中传递铁磁耦合作用，而Mn(II)配合物整体表现为反铁磁相互作用。