Lanthanide-based entangled coordination polymers connected by thiophene-2,5-dicarboxylate: solvothermal syntheses, crystal structures, luminescence and magnetic properties

Abstract

Nine novel coordination polymers (CPs) with the formulas [M₆(TDA)₉(DEF)₅(H₂O)₃]_n [M = Ce (1), Pr (2), Nd (3), Sm (4)], [Eu₄(TDA)₆(DEF)₃(H₂O)₂]_n (5), [Gd₂(TDA)₃(DEF)₂]_n·H₂O (6), [Tb₂(TDA)₃(DEF)₂]_n·0.5H₂O (7), [Dy₂(TDA)₃(DEF)₂]_n·H₂O (8) and [Yb₂(TDA)₃(DEF)₂]_n·0.5H₂O (9) (TDA = 2,5-thiophenedicarboxylate anion and DEF = diethylformamide) have been synthesized at different temperatures in a DEF–H₂O solvent system under solvothermal conditions. All the compounds were characterized by single crystal X-ray diffraction analysis (XRD), Fourier transformation vibrational spectroscopy (FT-IR) and thermal analysis (TGA). Structural analyses of CPs 1–4 reveal that the polymers crystallize in the orthorhombic space group Pna2₁ and form 3D frameworks with large volumes 10 378.1(5), 10 230.5(5), 10 171.9(5) and 10 077.1(11) ų, respectively. The M(III) ions of CPs 1–4 exhibit nine and eight coordination numbers with diverse geometries. Structural analyses of CPs 5 and 6–9 unveil that the polymers crystallize in the monoclinic system, with space groups P2₁ and P2/c, respectively, forming a 3D network. The TDA ligand exhibits two coordination modes [(κ¹-κ¹)–(κ¹-κ¹)-μ₄ and (κ²-κ¹-μ₂)–(κ¹-κ¹)-μ₅] which interconnect the metal ions to generate 3D novel metal–organic frameworks. The luminescence properties of 4, 5, 7 and 8, and the magnetic properties of 6–8 were investigated.