Two Types of New Three-Dimensional d–f Heterometallic Coordination Polymers Based on 2‑(Pyridin-3-yl)‑1<i>H</i>‑Imidazole-4,5-Dicarboxylate and Oxalate Ligands: Syntheses, Structures, Luminescence, and Magnetic Properties

Two types of new d–f heterometallic coordination frameworks, [Ln₂M­(μ₃-HPyIDC)₂(ox)₂(H₂O)₄]·4H₂O [Ln = Sm, M = Co (<b>1</b>); Ln = Sm, M = Fe (<b>2</b>); Ln = Eu, M = Co (<b>3</b>); Ln = Eu, M = Fe (<b>4</b>); Ln = Gd, M = Co (<b>5</b>); H₃PyIDC = 2-(pyridine-3-yl)-1<i>H</i>-4,5-imidazoledicarboxylic acid; ox = oxalate] for type <b>I</b> and [Ln₂Ag₃(μ₅-PyIDC)­(μ₆-PyIDC)­(μ₂-OH)­(ox)­(H₂O)₂] [Ln = Sm (<b>6</b>); Gd (<b>7</b>); Tb (<b>8</b>); Dy (<b>9</b>)] for type <b>II</b>, were prepared under hydrothermal conditions and structurally characterized. Complexes <b>1</b>–<b>5</b> are isostructural, exhibiting three-dimensional (3D) heterometallic networks with <b>pcu</b> topology based on the linkages of two-dimensional (2D) lanthanide–oxalate layers and pillar-like M­(HPyIDC)₂ (M = Fe, Co) subunits. Complexes <b>6</b>–<b>9</b> are also isomorphous and display another type of 3D heterometallic coordination framework built through the connections of 2D lanthanide–oxalate layers and one-dimensional (1D) Ag₂(PyIDC)₂ chains. Interestingly, the oxalate ligands in complexes <b>6</b>–<b>9</b> are produced by the in situ decarboxylation of the H₃PyIDC ligand in the presence of 4,4′-bipyridine (4,4<b>′</b>-bpy). The photoluminescence, thermal stabilities, and magnetic properties of the selected complexes were also investigated