Topological Diversities\nand Luminescent Properties\nof Lanthanide Metal–Organic Frameworks Based on a Tetracarboxylate\nLigand

Abstract

The\nreaction of 5,5′-(1,2-ethynediyl)­bis­(1,3-benzenedicarboxylic\nacid) (H₄EBDC) and dinuclear lanthanide building blocks\ngenerates five new three-dimensional lanthanide metal–organic\nframeworks (Ln-MOFs) with different topologies under mild conditions.\nIsomorphic compounds |C₂H₇N|[Ln₂(EBDC)­(NO₃)₂(C₃H₇NO)₄] [Ln\n= Eu (<b>1</b>), Tb (<b>2</b>), or Er (<b>3</b>)]\ncrystallize in monoclinic symmetry space group <i>C</i>2/<i>c</i> and adopt <b>PtS</b> topology. Under modified conditions,\nnew phases |(NO₃)_0.5(H₃O)_0.5|[Yb₂(EBDC)­(NO₃)₂(C₃H₇NO)₄] (space group <i>C</i>2/<i>c</i>, compound <b>4</b>) and |(H₃O)₂(C₃H₇NO)_2.5|[Eu₂(EBDC)₂(C₃H₇NO)­(H₂O)] (space group <i>P</i>2₁/<i>c</i>, compound <b>5</b>) are obtained. In <b>4</b>, both of the inorganic and organic\nbuilding blocks can be simplified into a four-coordinate node, forming\nan <b>Lvt</b> topological network. For compound <b>5</b>, the dinuclear Ln unit works as an 8-connected node and the organic\nligand serves as a 4-connected node; these two kinds of nodes connect\nand then present an unprecedented (4,8)-connected topology. The aforementioned\nLn-MOFs are all characterized by elemental analysis, infrared spectroscopy,\nand thermogravimetric analysis, and their luminescent properties have\nbeen studied, showing emission characteristic of inorganic species\nat room temperature.