Two Types of Cu-Ln Heterometallic Coordination Polymers with 2-Hydroxyisophthalate: Syntheses, Structures, and Magnetic Properties

Abstract

Two types of Cu-Ln heterometallic coordination polymers (CPs), [Ln4Cu8(ipO)8(ox)2(H2O)12] (Ln = Sm (1); Eu (2); ipO = 2-hydroxyisophthalate; ox = oxalate) (type I) and [Ln2Cu6(ipO)6(H2O)12] [Ln = Gd (3); Tb (4); Dy (5)] (type II), were synthesized under the same hydrothermal conditions and structurally characterized. The first type of CPs displays a three-dimensional framework with a rare case of MoGe2 topology based on {Cu8} and {Ln2} secondary building units (SBUs), while the second type of CPs exhibits a chain structure built up from {Cu6} SBUs and Ln ions. Both of the {Cu8} and {Cu6} SBUs consist of planar [Cu2(ipO)2]2– units linked together by weak Cu–O bonds and π–π interactions. The structural variation from type I to type II can be ascribed to different reactions of H3ipO ligands induced by lanthanide ions. The magnetic investigations revealed that 3 displays a magnetocaloric effect (MCE) with a maximum −ΔSm value of 13.97 J kg–1 K–1 for ΔH = 50 kOe at 4.0 K. It was also found that 5 displays fiel...