Wells–Dawson Cages as Molecular Refrigerants

Five clusters with the general formula [Ni6Gd6(μ3-OH)2(μ2-OAc)2(O3PR)6(O2CtBu)16], where R = methyl (1), phenyl (2), n-hexyl (3), benzyl (4), n-octyl (5), have been prepared. All of the clusters have a {Ni6Gd6P6} core that can be related to the Wells–Dawson ion. We have also prepared analogues where the gadolinium is replaced with diamagnetic yttrium: [Ni6Y6(μ3-OH)2(μ2-OAc)2(O3PR)6(O2CtBu)16] (R = methyl (6), n-hexyl (7), benzyl (8), n-octyl (9)), allowing the magnetic exchange within the {Ni3} units to be analyzed by modeling as the sum of two noninteracting isosceles triangles. The variation in the magnetic entropy changes for magnetization (−ΔSM) among compounds 1–5 could be attributed not only to the molecular weight of the compounds but also to intramolecular magnetic interactions.本研究制备了五个通式为[Ni₆Gd₆(μ₃-OH)₂(μ₂-OAc)₂(O₃PR)₆(O₂CtBu)₁₆]的团簇，其中取代基R分别为甲基（1）、苯基（2）、正己基（3）、苄基（4）与正辛基（5）。所有团簇均具有{Ni₆Gd₆P₆}金属核心，其结构可与Wells-Dawson离子（Wells–Dawson ion）类比。本研究还合成了以抗磁性钇替代钆的同系物：[Ni₆Y₆(μ₃-OH)₂(μ₂-OAc)₂(O₃PR)₆(O₂CtBu)₁₆]（R分别为甲基（6）、正己基（7）、苄基（8）与正辛基（9）），该类同系物可通过将{Ni₃}单元建模为两个无相互作用的等腰三角形之和，实现对{Ni₃}单元内磁交换相互作用的分析。化合物1至5的磁化强度磁熵变（−ΔS_M）差异，不仅可归因于化合物的分子量，还与分子内磁相互作用相关。