Abstract
Following a novel synthetic strategy where the strong uniaxial ligand field generated by the Ph3SiO− (Ph3SiO−=anion of triphenylsilanol) and the 2,4‐di‐tBu‐PhO− (2,4‐di‐tBu‐PhO−=anion of 2,4‐di‐tertbutylphenol) ligands combined with the weak equatorial field of the ligand LN6, leads to [DyIII(LN6)(2,4‐di‐tBu‐PhO)2](PF6) (1), [DyIII(LN6)(Ph3SiO)2](PF6) (2) and [DyIII(LN6)(Ph3SiO)2](BPh4) (3) hexagonal bipyramidal dysprosium(III) single‐molecule magnets (SMMs) with high anisotropy barriers of U eff=973 K for 1, U eff=1080 K for 2 and U eff=1124 K for 3 under zero applied dc field. Ab initio calculations predict that the dominant magnetization reversal barrier of these complexes expands up to the 3rd Kramers doublet, thus revealing for the first time the exceptional uniaxial magnetic anisotropy that even the six equatorial donor atoms fail to negate, opening up the possibility to other higher‐order symmetry SMMs.
Highlights
Hexagonal bipyramidal dysprosium(III) single-molecule magnets (SMMs) with high anisotropy barriers of Ueff = 973 K for 1, Ueff = 1080 K for 2 and Ueff = 1124 K for 3 under zero applied dc field
Ab initio calculations predict that the dominant magnetization reversal barrier of these complexes expands up to the 3rd Kramers doublet, revealing for the first time the exceptional uniaxial magnetic anisotropy that even the six equatorial donor atoms fail to negate, opening up the possibility to other higher-order symmetry SMMs
Among the very few structurally characterized mononuclear lanthanide complexes with hexagonal bipyramidal geometry only very small Ueff barriers are observed and SMM behavior is only seen on application of a dc field, owing to weak axiality and/or the presence of unwanted electron donating atoms in the equatorial plane.[10]
Summary
We targeted the formation of the required weak equatorial plane of the desired hexagonal bipyramid by isolating the precursor [DyIIILN6(CH3CO2)2](CH3CO2)·9 H2O (Supporting Information, Figure S1 and Table S1).[11] We sought to replace the weak axial bidentate acetate ligands with stronger anionic donors (anion of 2,4-di-tertbutylphenol and anion of triphenylsilanol). Schiff base ligand formed from 2,6-diacetylpyridine and ethylenediamine) with two SiÀOÀ or RÀOÀ based ligands above and below the equatorial plane, respectively (Figure 1; Supporting Information, Figures S2, S3), resulting in a strongly axial hexagonal bipyramidal geometry.
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