The Nature of the Bridging Anion Controls the Single-Molecule Magnetic Properties of DyX4M 12-Metallacrown‑4 Complexes

A family of DyX4M­(12-MCMnIII(N)shi-4) compounds were synthesized and magnetically characterized (X = salicylate, acetate, benzoate, trimethylacetate, M = NaI or KI). The bridging ligands were systematically varied while keeping the remainder of the MC-geometry constant. The type of monovalent cation, necessary for charge balance, was also altered. The dc magnetization and susceptibility of all compounds were similar across the series. Regardless of the identity of the countercation, the Dy­(Hsal)4M 12-MC-4 compounds were the only compounds to show frequency-dependent ac magnetic susceptibility, a hallmark of single-molecule magnetism. This indicates that the nature of the bridging ligand in the 12-MCMnIII(N)shi-4 compounds strongly affects the out-of-phase magnetic properties. The SMM behavior appears to correlate with the pKa of the bridging ligand.本研究合成了一系列DyX₄M(12-MCMnIII(N)shi-4)类化合物，并对其开展了磁学表征（其中X为水杨酸盐（salicylate）、乙酸盐（acetate）、苯甲酸盐（benzoate）、三甲基乙酸盐（trimethylacetate），M为NaI或KI）。实验过程中，在保持MC配位几何构型其余部分不变的前提下，系统调控了桥联配体的种类；同时也调整了用于维持电荷平衡的一价阳离子类型。该系列所有化合物的直流磁化强度与磁化率均表现出相似的特征。无论抗衡阳离子的种类如何，Dy(Hsal)₄M 12-MC-4类化合物是唯一表现出频率依赖性交流磁化率的物种，该特性是单分子磁体特性（single-molecule magnetism）的标志性表现。这表明，12-MCMnIII(N)shi-4类化合物中桥联配体的本质，对其异相磁学性质具有显著影响。单分子磁体（SMM）行为似乎与桥联配体的pKa值存在相关性。