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 (H(2)MMA) and isonicotinic acid (HINA), two-dimensional (2D) [Ln(2)(MMA)(2)(INA)(2)(H2O)(3)] (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 H(2)MMA or the type of Ln(3+) ion. Complexes 1 and 2 contain two kinds of ID lanthanide chain units (wave and linear), which are alternately linked by the MMA(2-) and INAligands to form a 2D layer structure. Complexes 3 and 4 also have a 2D layer structure, consisting of 1D linear lanthanide chain units, MMA(2-) and INA(-) linkers. Compound 5 shows a 1D linear chain structure, in which the neighboring Dy3+ ions are fastened by the carboxylate groups from MNIA(2-) and INA(-) ligands. The magnetic studies reveal the presence of ferromagnetic Gd center dot center dot center dot Gd coupling in the ID chain units of 2 and 3, which display significant cryogenic magnetocaloric effects with a maximum -Delta S-m, value of 34.32 J kg(-1) at 3 K and 36.02 J kg(-1) K-1 at 2 K for Delta H = 7 T, respectively. Furthermore, the solid-state photophysical properties of 1 and 4 exhibit strong characteristic Eu3+ and Tb3+ photoluminescent emission in the visible region, indicating that Eu- and Tb-based luminescences are sensitized effectively by the energy transfer from the INAligand to the metal centers.