Three Types of Lanthanide Coordination Polymers with Methylmalonate and Isonicotinate as Coligands: Structures, Luminescence, and Magnetic Properties

Three types of lanthanide coordination polymers based on mixed methylmalonic acid (H2MMA) and isonicotinic acid (HINA), two-dimensional (2D) [Ln2(MMA)2(INA)2(H2O)3]n (Ln = Eu (1); Gd (2)) and [Ln(MMA)(INA)(H2O)2]n (Ln = Gd (3); Tb (4)) as well as one-dimensional (1D) [Dy(MMA)(INA)(H2O)2]n (5), have been hydrothermally synthesized, which can be controlled by the usage amount of H2MMA or the type of Ln3+ ion. Complexes 1 and 2 contain two kinds of 1D lanthanide chain units (wave and linear), which are alternately linked by the MMA2– and INA– ligands to form a 2D layer structure. Complexes 3 and 4 also have a 2D layer structure, consisting of 1D linear lanthanide chain units, MMA2– and INA– linkers. Compound 5 shows a 1D linear chain structure, in which the neighboring Dy3+ ions are fastened by the carboxylate groups from MMA2– and INA– ligands. The magnetic studies reveal the presence of ferromagnetic Gd···Gd coupling in the 1D chain units of 2 and 3, which display significant cryogenic magnetocaloric effec...