Linking heterometallic Cu–Ln chain units with a 2-methylenesuccinate bridge to form a 2D network exhibiting a large magnetocaloric effect

Abstract

Four two-dimensional heterometallic Cu–Ln coordination polymers based on the 2-methylenesuccinic acid (H₂MSA) ligand, {[Ln₂Cu(MSA)₄(H₂O)₆]·2H₂O}_n(Ln = La (1); Gd (2); Tb (3); Dy (4)), have been obtained under hydrothermal conditions. Complexes 1–4 bear a feature of one-dimensional [Ln₂Cu] chains linked by 2-methylenesuccinate (MSA²⁻) bridges to form a 2D layer structure. Magnetic studies suggest the presence of weak antiferromagnetic Gd⋯Gd coupling and weak ferromagnetic Cu⋯Gd coupling in the 1D [Gd₂Cu] chain unit of 2. The magnetic entropy change (−ΔS_m) reached 36.05(1) J K⁻¹ kg⁻¹ for 2, making it an attractive refrigerant for low-temperature applications.