Two Types of Lanthanide Coordination Polymers Based on a Homophthalate Ligand Exhibiting Luminescence and a Significant Magnetocaloric Effect

Abstract

Two types of lanthanide coordination polymers based on homophthalic acid (H2HPA), one-dimensional {[Ln(HPA)(NO3)(H2O)2]·H2O}n (Ln = Eu (1); Gd (2); Tb (3); Dy (4)) and two-dimensional {[Ln2(HPA)3(H2O)2]·H2O}n (Ln = Eu (5); Gd (6); Tb (7); Dy (8)), were solvothermally synthesized. Compounds 1–4 show a one-dimensional (1D) linear chain structure consisting of a HPA2– linker and [Ln2] cluster unit. Compounds 4–8 are crystallographically isostructural and contain 1D lanthanide-carboxylate building units [Ln4(CO2)10]n built from the adjacent Ln3+ ions and carboxyl groups of the H2HPA ligands, which can further give two-dimensional layer structures via the link of HPA2–. The magnetic studies reveal that complexes 2 and 6 with isotropic Gd3+ ion exhibit significant cryogenic magnetocaloric effects with a maximum −ΔSm value of 35.58 and 35.41 J kg–1 K–1 at 2 K and 7 T, respectively. In addition, the solid-state photophysical properties of 1/5 and 3/7 respectively display strong characteristic Eu3+ and Tb3+ photol...