Insight into D6h Symmetry: Targeting Strong Axiality in Stable Dysprosium(III) Hexagonal Bipyramidal Single-Ion Magnets

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 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, 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.

Heteroleptic Lanthanide Complexes Coordinated by Tripodal Tetradentate Ligand: Synthesis, Structure, and Magnetic and Photoluminescent Properties

“…16 However, the examples of non-organometallic high performance lanthanide SMMs based on classical ligands involving nitrogen and/or oxygen atoms are still relatively scarce. 10,[17][18][19][20][21][22][23] In this sense, we have recently reported the synthesis and magnetic properties of a series of original heteroleptic lanthanides complexes [Ln(Tpm)X 3 ] (Ln = Tb, Dy, Er; Tpm = tris (3,5dimethylpyrazolyl)methane; X  = NO 3  , Cl  ) based on a tripodal tris(pyrazolyl)methane ligand. 24 These complexes exhibit a field-induced slow relaxation of the magnetization which is highly dependent on both, the lanthanide ion's and counter anion's nature.…”

Field-induced SIM behaviour in early lanthanide(iii) organophosphates containing 18-crown-6

“…Like K + , the Ln(III) ions are the best fit for the cavity of 18-crown-6, while in the case of smaller crown ethers, Ln(III) ions sit out of the cavity. As crown ether oxygen centers interact only weakly with the Ln(III) centres, using a ligand field comprising strong axial ligands and weak equatorial 18-crown-6 [32][33][34] would be expected as the ideal strategy for designing high-performance SIMs derived from oblate lanthanides. [33][34][35][36][37][38] Based on these earlier observations and building up on our recent results on phosphorus ligand based SIMs, [39][40][41][42] we report here a series of early Ln(III) (Ln: Ce, Pr, Nd, Sm and Eu) organophosphate complexes [{(18-crown-6)Ln(dippH 4) and Eu (5)], derived from 2,6-diisopropylphenylphosphate (dippH 2 ) as axial ligands, containing 18-crown-6 ligand in the equatorial positions.…”

“…A number of oblate-shaped Ln(III) ion (especially Dy(III) ion) based singleion magnets with an hexagonal equatorial plane are found to have significantly high barrier heights of spin reversal. 32,33,[43][44][45][46][47][48] Such complexes with a local hexagonal bipyr-amidal geometry fulfill the strong magnetic axiality and high coordination number providing air stability to the complexes.…”

Predesigned rigid dysprosium(III) single-molecule magnets exhibit preserved superparamagnetism in solution

“…The key ingredient for high T B SMMs is to use the dysprosium(III) ion, a heavy lanthanide element with nine unpaired 4f electrons, which has a ground state of 6 H 15/2 with signi cant magnetic anisotropy. [14][15][16] With proper axial crystal eld U eff of dysprosium(III) based SMMs can be largely enhanced, which now have been widely achieved. [17][18][19][20] However, a severe drop of magnetization at zero-eld owing to quantum tunneling of magnetization (QTM) remains a challenge for such high barrier SMMs.…”