A Series Three-Dimensional LnCr (Ln = Gd, Tb, Er) Heterometallic Cluster-Based Coordination Polymers Containing Interesting Nanotubes Exhibiting High Magnetic Entropy.

A series of novel 3D 3d-4f heterometallic cluster-based coordination polymers, [LnCr(μ-O)(μ-O)(NA)(HO)]·HO (Ln = , , ; HNA nicotinic acid; = 13 (), 11.33 (), 15 ()), have been successfully synthesized by hydrothermal method using nicotinic acid as bridging ligand. The single-crystal X-ray diffraction (SCXRD) analysis indicated that the basic unit of LnCr shows a butterfly-shaped structure. Furthermore, each LnCr cluster connects with other four LnCr clusters by bridging NA ligands to form a 3D structure containing interesting 1D honeycomb-shaped coordination nanotubes. The variable temperature magnetic susceptibility measurements of compound revealed that the existence of antiferromagnetic (AF) coupling between the metal ions in the GdCr clusters. Field-dependent isothermal magnetization studies displayed that the magnetic entropy change (-Δ) value of reached 22.05 J K kg.