On Approaching the Limit of Molecular Magnetic Anisotropy: A Near‐Perfect Pentagonal Bipyramidal Dysprosium(III) Single‐Molecule Magnet

Abstract

We report a monometallic dysprosium complex, [Dy(O Bu) (py) ][BPh ] (5), that shows the largest effective energy barrier to magnetic relaxation of U =1815(1) K. The massive magnetic anisotropy is due to bis-trans-disposed tert-butoxide ligands with weak equatorial pyridine donors, approaching proposed schemes for high-temperature single-molecule magnets (SMMs). The blocking temperature, T , is 14 K, defined by zero-field-cooled magnetization experiments, and is the largest for any monometallic complex and equal with the current record for [Tb N {N(SiMe ) } (THF) ].

Systematic studies of hexanuclear {MIII4LnIII2} complexes (M = Fe, Ga; Ln = Er, Ho): structures, magnetic properties and SMM behavior

“…The curves for 6 and {5 + 6} show a steepening of the decrease in χT below about 8 K, which was interpreted as the effect of antiferromagnetic Dy III -Dy III interactions superimposed on the thermal depopulation of Dy III MJ sub-levels. 29 The curve for Fe4Dy2 (7), by contrast shows a significant upturn below 10 K, which is significantly larger than those seen for the Er III analogues. Such an upturn indicates that the Fe III -Dy III interactions in 7 have forced the two Dy III spins into a coparallel ferromagnetic arrangement.…”

“…25 Therefore, in order to maximize the magnetic anisotropy, a sandwich-type ligand geometry with harder or negatively-charged ligand atoms predominantly in axial positions is expected to be appropriate for Dy III , while a ligand field with such harder atoms mainly in an equatorial coordination positions should be necessary for Er III . [26][27][28][29][30][31][32] However, 3d-Er III coordination clusters showing SMM behavior are rare in comparison to 3d-Dy III or 3d-Tb III clusters. 17,18,33 Sessoli et al recently published two isostructural Ln(trensal) complexes with identical ground state J = 15/2, namely the easy-plane Dy(trensal) and easy-axis Er(trensal).…”

Molecular single-ion magnets based on lanthanides and actinides: Design considerations and new advances in the context of quantum technologies

“…Over the last fifteen years or so, the field of molecular magnetism has undergone a shift of focus away from polynuclear complexes towards SIMs, and in particular toward those containing f-block elements [32][33][34][35][36][37][38][39][40]. This change in direction was largely driven by research progress, being realised that the parameters defining the magnetic relaxation barrier of SMMs, the total spin (S) and the axial anisotropy (D), are not easily achievable by simply scaling molecules to contain more spin-bearing atoms.…”

“…Ab-initio models have been routinely employed to predict which ligand environments allow for the best optimisation of the spin relaxation times [49][50][51], in view of fabricating molecular devices that could store and process information above cryogenic temperatures. Recent work has made significant gains in this direction, with reports of slow magnetic relaxation at temperatures as high as 100 K and magnetic blocking at 5-30 K in Dy- [32][33][34][35][36], Er- [52,53] and Tb- [54,55] SIMs. Other notable achievements are the observation of Rabi oscillations in f-element single molecules [56][57][58][59], and the detection of 'atomic clock transitions' in a Ho-SIM system [60].…”

Future Directions for Transuranic Single Molecule Magnets

“…Moving to the 4f block allowed one to partially overcome the impasse. Rare earths, with unquenched orbital degrees of freedom, exhibit a much larger single-ion anisotropy than transition metals, resulting in U eff values above 1800 K [7] and remanent magnetization up to about 60 K [8]. However, the exchange interaction between rare earths is usually smaller than in transition metals, so that the advantage offered by a coupled multi-centre structure is lost.…”