Abstract
Dysprosium single-molecule magnets (SMMs) with two mutually trans- anionic ligands have shown large crystal field (CF) splitting, giving record effective energy barriers to magnetic reversal (Ueff) and hysteresis temperatures (TH). However, these complexes tend to be bent, imposing a transverse field that reduces the purity of the mJ projections of the CF states and promotes magnetic relaxation. A complex with only one charge-dense anionic ligand could have more pure CF states, and thus high Ueff and TH. Here we report an SMM with this topology, a half-sandwich Dy(III) complex [Dy(Cp*)(FPh)6][{Al[OC(CF3)3]3}2(μ-F)]2 (1-Dy; Cp* = C5Me5), and its Y(III) analogue 1-Y; 1-Dy exhibits Ueff = 545(30) cm–1 and TH = 14 K at sweep rates of 22 Oe s–1. The Cp* ligand imposes a strong axial CF, which is assisted by one axial fluorobenzene; the five equatorially-bound neutral fluorobenzenes present only weak transverse interactions to give a pseudo-pentagonal bipyramidal geometry. The salt metathesis reaction of 1-Y with KCpʹʹʹ (Cpʹʹʹ = {C5H2(SiMe3)3-1,2,4}) gave the sandwich complex [Y(Cpʹʹʹ)(Cp*)(FPh)2][{Al[OC(CF3)3]3}2(μ-F)] (4-Y), showing that the fluorobenzenes of 1-Y are easily displaced. We envisage that these methodologies could be adapted in future to prepare high-performance axial Dy SMMs with ligands that are more sterically demanding than Cp*.
Original language | English |
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Journal | Chemical Science |
Early online date | 4 Dec 2024 |
DOIs | |
Publication status | Published - 1 Jan 2025 |
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EPSRC National Research Facility for Electron Paramagnetic Resonance
Collison, D. (Academic lead), Mcinnes, E. (Academic lead), Tuna, F. (Academic lead), Bowen, A. (Academic lead), Shanmugam, M. (Senior Technical Specialist), Brookfield, A. (Technical Specialist), Fleming, E. (Other) & Cliff, M. (Platform Lead)
FSE ResearchFacility/equipment: Facility