Topological Diversities and Luminescent Properties of Lanthanide Metal–Organic Frameworks Based on a Tetracarboxylate Ligand

The
reaction of 5,5′-(1,2-ethynediyl)­bis­(1,3-benzenedicarboxylic
acid) (H4EBDC) and dinuclear lanthanide building blocks
generates five new three-dimensional lanthanide metal–organic
frameworks (Ln-MOFs) with different topologies under mild conditions.
Isomorphic compounds |C2H7N|[Ln2(EBDC)­(NO3)2(C3H7NO)4] [Ln
= Eu (1), Tb (2), or Er (3)]
crystallize in monoclinic symmetry space group C2/c and adopt PtS topology. Under modified conditions,
new phases |(NO3)0.5(H3O)0.5|[Yb2(EBDC)­(NO3)2(C3H7NO)4] (space group C2/c, compound 4) and |(H3O)2(C3H7NO)2.5|[Eu2(EBDC)2(C3H7NO)­(H2O)] (space group P21/c, compound 5) are obtained. In 4, both of the inorganic and organic
building blocks can be simplified into a four-coordinate node, forming
an Lvt topological network. For compound 5, the dinuclear Ln unit works as an 8-connected node and the organic
ligand serves as a 4-connected node; these two kinds of nodes connect
and then present an unprecedented (4,8)-connected topology. The aforementioned
Ln-MOFs are all characterized by elemental analysis, infrared spectroscopy,
and thermogravimetric analysis, and their luminescent properties have
been studied, showing emission characteristic of inorganic species
at room temperature.

以5,5′-(1,2-乙炔二基)双(1,3-苯二甲酸)（H4EBDC）与双核镧系构筑单元为反应物，在温和条件下合成了5种具有不同拓扑结构的新型三维镧系金属有机框架（Ln-MOFs）。同构化合物|C2H7N|[Ln2(EBDC)(NO3)2(C3H7NO)4]（其中Ln分别为铕（1）、铽（2）或铒（3））以单斜晶系空间群C2/c结晶，并呈现PtS拓扑结构。在优化反应条件后，得到了两个新物相：|(NO3)0.5(H3O)0.5|[Yb2(EBDC)(NO3)2(C3H7NO)4]（空间群C2/c，化合物4）与|(H3O)2(C3H7NO)2.5|[Eu2(EBDC)2(C3H7NO)(H2O)]（空间群P21/c，化合物5）。在化合物4中，无机与有机构筑单元均可简化为四配位节点，由此构筑得到Lvt拓扑网络。对于化合物5，双核镧系单元充当八配位节点，有机配体则作为四配位节点；两类节点相互连接后形成了前所未有的(4,8)-连接拓扑结构。上述所有Ln-MOFs均通过元素分析、红外光谱以及热重分析进行了表征，并对其室温下的发光性能开展了研究，展现出对应无机物种的特征发射。