Mixed-valence dilanthanide complexes of the type (Cp^iPr5)₂Ln₂I₃ (Cp^iPr5 = pentaisopropylcyclopentadienyl; Ln = Gd, Tb, Dy) featuring a direct Ln–Ln σ-bonding interaction have been shown to exhibit well-isolated high-spin ground states and, in the case of the Tb and Dy variants, a strong axial magnetic anisotropy that gives rise to a large magnetic coercivity. Here, we report the synthesis and characterization of two new mixed-valence dilanthanide compounds in this series, (Cp^iPr5)₂Ln₂I₃ (1-Ln; Ln = Ho, Er). Both compounds feature a Ln–Ln bonding interaction, the first such interaction in any molecular compounds of Ho or Er. Like the Tb and Dy congeners, both complexes exhibit high-spin ground states arising from strong spin–spin coupling between the lanthanide 4f electrons and a single σ-type lanthanide–lanthanide bonding electron. Beyond these similarities, however, the magnetic properties of the two compounds diverge. In particular, 1-Er does not exhibit observable magnetic blocking or slow magnetic relaxation, while 1-Ho exhibits magnetic blocking below 28 K, which is the highest temperature among Ho-based single-molecule magnets, and a spin reversal barrier of 556(4) cm^–1. Additionally, variable-field magnetization data collected for 1-Ho reveal a coercive field of greater than 32 T below 8 K, more than 6-fold higher than observed for the bulk magnets SmCo₅ and Nd₂Fe₁₄B, and the highest coercive field reported to date for any single-molecule magnet or molecule-based magnetic material. Multiconfigurational calculations, supported by far-infrared magnetospectroscopy data, reveal that the stark differences in magnetic properties of 1-Ho and 1-Er arise from differences in the local magnetic anisotropy of the lanthanide centers.

中文翻译：

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混合价单分子磁体 (CpiPr5)2Ho2I3 矫顽力超过 30 T


混合价二镧系元素络合物 (Cp ^iPr5 ) ₂ Ln ₂ I ₃ (Cp ^iPr5 = 五异丙基环戊二烯基；Ln = Gd、Tb、Dy）具有直接的 Ln-Ln σ 键相互作用，已被证明表现出良好隔离的高自旋基态，并且在 Tb 和 Dy 变体的情况下，具有强轴向磁性各向异性，产生大的磁矫顽力。在这里，我们报告了该系列中两种新型混合价二镧系元素化合物的合成和表征，(Cp ^iPr5 ) ₂ Ln ₂ I ₃ 。此外，收集的 1-Ho 变场磁化数据显示，在 8 K 以下，矫顽磁场大于 32 T，比大块磁体 SmCo ₅ 和 Nd ₂ Fe ₁₄ B，以及迄今为止报道的任何单分子磁体或基于分子的磁性材料的最高矫顽场。 由远红外磁谱数据支持的多构型计算表明，1-Ho 和 1-Er 的磁特性的明显差异源于稀土中心局部磁各向异性的差异。