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.