Coercive Fields Exceeding 30 T in the Mixed-Valence Single-Molecule Magnet (Cp iPr5 ) 2 Ho 2 I 3

• Published in: Journal of the American Chemical Society 2024-07, Vol.146 (27), p.18714-18721
• Main Authors: Kwon, Hyunchul, McClain, K Randall, Kragskow, Jon G C, Staab, Jakob K, Ozerov, Mykhaylo, Meihaus, Katie R, Harvey, Benjamin G, Choi, Eun Sang, Chilton, Nicholas F, Long, Jeffrey R
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.4c06250

Mixed-valence dilanthanide complexes of the type (Cp ) Ln I (Cp = 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 ) Ln I ( ; 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, does not exhibit observable magnetic blocking or slow magnetic relaxation, while 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 . Additionally, variable-field magnetization data collected for reveal a coercive field of greater than 32 T below 8 K, more than 6-fold higher than observed for the bulk magnets SmCo and Nd Fe B, 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 and arise from differences in the local magnetic anisotropy of the lanthanide centers.