Temperature-Dependent\nStructures of Lanthanide Metal–Organic\nFrameworks Based on Furan-2,5-Dicarboxylate and Oxalate

Abstract

Two series of lanthanide metal–organic frameworks,\n[Ln­(FDA)­(OX)_0.5(H₂O)₂]·(H₂O) (<b>1Ln</b>) (Ln = Pr <b>1</b>, Nd <b>2</b>, Eu <b>3</b>, Gd <b>4,</b> Tb <b>5</b>), [Ln­(FDA)­(OX)_0.5(H₂O)₂]·(H₂O) (<b>2Ln</b>) (Ln = Sm <b>6</b>, Tb <b>7</b>, Dy <b>8</b>, Ho <b>9</b>, Yb <b>10</b>) (OX = oxalate),\nhave been prepared by reacting Ln­(NO₃)₃·6H₂O with furan-2,5-dicarboxylic acid (H₂FDA) at different\ntemperatures under hydrothermal conditions. All the complexes are\ncharacterized by elemental analysis, IR, X-ray powder diffraction,\nand single-crystal X-ray diffraction. Structure analyses show that <b>1Ln</b> and <b>2Ln</b> are supramolecular isomerisms. <b>1Ln</b> possesses a three-dimensional network with monoclinic\nspace group <i>P</i>2₁/<i>c</i>, whereas <b>2Ln</b> exhibits a three-dimensional framework with monoclinic\nspace group <i>C</i>2/<i>c</i>. The distinct architectures\nof these two series of ten complexes indicated that the reaction temperature\nplays an important role in the formation of such coordination structures.\nMeanwhile, the photoluminescent properties of <b>4</b>, <b>5</b>, <b>7</b>, and <b>8</b> are also investigated\nin the solid state at room temperature.