Exploring the functional relation of magnetic density and magnetocaloric effect based on a dinuclear system

Cl--templated coordination polymers constructed from dragonfly-like Ln4 clusters exhibiting excellent magnetothermal properties

Lanthanide clusters with high magnetic entropy and an exquisite structure have always been a hot research direction. Herein, two delicately structured lanthanide clusters were synthesized using isonicotinic acid (HIN) as a ligand by the solvothermal method, namely {[Gd4(IN)4(μ3-OH)4(OAc)2(H2O)6]·Cl2·7H2O}n (1) and {[Dy4(IN)4(μ3-OH)4(OAc)2(H2O)6]·Cl2·8H2O}n (2). Structural analysis indicates that the two compounds exhibit comparable structures, and both have the same cubane-like Ln4 metal skeleton and form an interesting dragonfly molecular configuration by connecting to HIN. Moreover, {Ln4} serves as the fundamental structural unit for the construction of a 1D channel of 1, with a diameter of approximately 10.08 Å, which is connected to each other by extra {Ln4} units to form an exquisite porous 3D structure of 1. Cl- exists as an anion-template in its 3D structure, balancing the charge and maintaining its structural stability. Magnetic measurements indicate that 1 exhibits a rather satisfactory magnetic entropy change, reaching a maximum value of -ΔSmaxm = 31.59 J kg-1 K-1 at 2 K for ΔH = 7 T.

A Series of High-Nuclear Gadolinium Cluster Aggregates with a Magnetocaloric Effect Constructed through Two-Component Manipulation

The serialized expansion of high-nuclear clusters usually includes the controlled variable method and changes only a single variable. However, changing both variables will greatly increase the complexity of the reaction simultaneously. Therefore, the use of a two-component regulation reaction is rare. Herein, we used a diacylhydrazone ligand (H₄L¹) with multidentate chelating coordination sites for the reaction with Gd(NO₃)₃·6H₂O under solvothermal conditions to obtain an example of 16-nucleus disc-shaped cluster 1 with a brucite structure. The overall structure of cluster 1 can be regarded as an equilateral triangle, which is formed by three (L¹)^4- ions that can be regarded as "sides" and wrap the four-layer metal center Gd(III) ions. Notably, upon simultaneous regulation of the substituent of the ligand and the coordination anion, heptanuclear gadolinium cluster 2 was obtained. Cluster 2 can be regarded as a butterfly structure, which was formed by connecting two Gd₃L² molecules that were not in the same plane and through the central Gd(III) ion as an intersection. Moreover, hexanuclear gadolinium cluster 3 was obtained by changing the ligand substituent and adding an auxiliary ligand. Cluster 3 can be regarded as a chair structure, which was composed of two molecules of diacylhydrazone ligand (L²)^4- wrapping vacant cubane shared by four vertices. This study was the first to construct a series of high-nuclear gadolinium clusters through two-component regulation manipulation. The study of the magnetocaloric effect showed that the maximum values of -ΔS_m for clusters 1-3 were 34.05, 29.04, and 24.32 J kg^-1 K^-1, respectively, when T = 2 K and ΔH = 7 T.