Tuning the magnetic anisotropy of metal ions remains highly interesting in the design of improved single-molecule magnets (SMMs). We herein report synthetic, structural, magnetic, and computational studies of four mononuclear CoII complexes, namely [Co(hfac)2 (MeCN)2 ] (1), [Co(hfac)2 (Spy)2 ] (2), [Co(hfac)2 (MBIm)2 ] (3), and [Co(hfac)2 (DMF)2 ] (4) (MeCN=acetonitrile, hfac=hexafluoroacetylacetone, Spy=4-styrylpyridine, MbIm=5,6-dimethylbenzimidazole, DMF=N,N-dimethylformamide), with distorted octahedral geometry constructed from hexafluoroacetylacetone (hfac) and various axial ligands. By a building block approach, complexes 2-4 were synthesized by recrystallization of the starting material of 1 from various ligands containing solution. Magnetic and theoretical studies reveal that 1-4 possess large positive D values and relative small E parameters, indicating easy-plane magnetic anisotropy with significant rhombic anisotropy in 1-4. Dynamic alternative current (ac) magnetic susceptibility measurements indicate that these complexes exhibit slow magnetic relaxation under external fields, suggesting field-induced single-ion magnets (SIMs) of 1-4. These results provide a promising platform to achieve fine tuning of magnetic anisotropy through varying the axial ligands based on Co(II) bis(hexafluoroacetylacetonate) complexes.

中文翻译：

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调整一类Co（II）双（六氟乙酰丙酮）配合物的磁各向异性。

在改进的单分子磁体（SMM）的设计中，调整金属离子的磁各向异性仍然非常有趣。我们在此报告了四个单核CoII配合物，即[Co（hfac）2（MeCN）2]（1），[Co（hfac）2（Spy）2]（2），[ Co（hfac）2（MBIm）2]（3）和[Co（hfac）2（DMF）2]（4）（MeCN =乙腈，hfac =六氟乙酰丙酮，Spy = 4-苯乙烯基吡啶，MbIm = 5,6-由六氟乙酰丙酮（hfac）和各种轴向配体构成的八面体几何变形的二甲基苯并咪唑（DMF = N，N-二甲基甲酰胺）。通过构造方法，通过从包含溶液的各种配体中将1的起始原料重结晶来合成配合物2-4。磁学和理论研究表明1-4具有较大的正D值和相对较小的E参数，表明1-4中的易平面磁各向异性具有明显的菱形各向异性。动态交流电（ac）的磁化率测量表明，这些复合物在外部磁场下显示出缓慢的磁弛豫，表明磁场感应的单离子磁体（SIM）为1-4。这些结果为通过改变基于Co（II）双（六氟乙酰丙酮）配合物的轴向配体实现磁各向异性的微调提供了一个有希望的平台。建议使用场感应的1-4的单离子磁体（SIM）。这些结果为通过改变基于Co（II）双（六氟乙酰丙酮）配合物的轴向配体实现磁各向异性的微调提供了一个有希望的平台。建议使用场感应的1-4的单离子磁体（SIM）。这些结果为通过改变基于Co（II）双（六氟乙酰丙酮）配合物的轴向配体实现磁各向异性的微调提供了一个有希望的平台。