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

Abstract

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 −ΔS^max_m = 31.59 J kg⁻¹ K⁻¹ at 2 K for ΔH = 7 T.