Dominance of cyclobutadienyl over cyclopentadienyl in the crystal field splitting in dysprosium single-molecule magnets
Durrant, James P.; Day, Benjamin M.; Tang, Jinkui; Mansikkamäki, Akseli; Layfield, Richard A. (2022-04-12)
J. P. Durrant, B. M. Day, J. Tang, A. Mansikkamäki, R. A. Layfield, Angew. Chem. Int. Ed. 2022, 61, e202200525; Angew. Chem. 2022, 134, e202200525, https://doi.org/10.1002/anie.202200525
© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
https://creativecommons.org/licenses/by/4.0/
https://urn.fi/URN:NBN:fi-fe2022071951800
Tiivistelmä
Abstract
Replacing a monoanionic cyclopentadienyl (Cp) ligand in dysprosium single-molecule magnets (SMMs) with a dianionic cyclobutadienyl (Cb) ligand in the sandwich complexes [(η⁴-Cb′′′′)Dy(η⁵-C₅Me₄tBu)(BH₄)]⁻ (1), [(η⁴-Cb′′′′)Dy(η⁸-Pn†)K(THF)] (2) and [(η⁴-Cb′′′′)Dy(η⁸-Pn†)]⁻ (3) leads to larger energy barriers to magnetization reversal (Cb′′′′=C₄(SiMe₃)₄, Pn†=1,4-di(tri-isopropylsilyl)pentalenyl). Short distances to the Cb′′′′ ligands and longer distances to the Cp ligands in 1–3 are consistent with the crystal field splitting being dominated by the former. Theoretical analysis shows that the magnetic axes in the ground Kramers doublets of 1–3 are oriented towards the Cb′′′′ ligands. The theoretical axiality parameter and the relative axiality parameter Z and Zrel are introduced to facilitate comparisons of the SMM performance of 1–3 with a benchmark SMM. Increases in Z and Zrel when Cb′′′ replaces Cp signposts a route to SMMs with properties that could surpass leading systems.
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