Large Spin‐Relaxation Barriers for the Low‐Symmetry Organolanthanide Complexes [Cp*₂Ln(BPh₄)] (Cp*=pentamethylcyclopentadienyl; Ln=Tb, Dy)

Abstract

Single-molecule magnets comprising one spin center represent a fundamental size limit for spin-based information storage. Such an application hinges upon the realization of molecules possessing substantial barriers to spin inversion. Axially symmetric complexes of lanthanides hold the most promise for this due to their inherently high magnetic anisotropies and low tunneling probabilities. Herein, we demonstrate that strikingly large spin reversal barriers of 216 and 331 cm(-1) can also be realized in low-symmetry lanthanide tetraphenylborate complexes of the type [Cp*2 Ln(BPh4 )] (Cp*=pentamethylcyclopentadienyl; Ln=Tb (1) and Dy (2)). The dysprosium congener showed hysteretic magnetization data up to 5.3 K. Further studies of the magnetic relaxation processes of 1 and 2 under applied dc fields and upon dilution within a matrix of [Cp*2 Y(BPh4 )] revealed considerable suppression of the tunneling pathway, emphasizing the strong influence of dipolar interactions on the low-temperature magnetization dynamics in these systems.

Phenalenyl-based mononuclear dysprosium complexes

“…On the other hand, the presence of these co-ligands in these systems reduces the three-fold symmetry of the whole molecule. Indeed, low-symmetry elements present in such a ligand field play an important role in facilitating tunneling or other magnetic relaxation processes [54]. This effect is consistent with the observation of true thermally activated relaxation resulting in a highly curved relaxation time down to the low temperature regime (Fig.…”

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

“…Along with organometallic sandwiched compounds, Long and co-workers have reported low-symmetry lanthanide complexes [(Cp*)2Ln(BPh4)] (Ln = Tb (23) and Dy (24)) with large spin reversal barriers of 311 K and 476 K, respectively [84]. Compound 24 showed hysteretic behaviour up to 5.3 K, with no remnant magnetisation due to pronounced QTM and a dipole-mediated magnetic avalanche.…”

Lanthanides and actinides: Annual survey of their organometallic chemistry covering the year 2014

“…These results clearly showed that the bent ligand fields presented within the complexes Cp * 2 Ln(BPh 4 ) (Ln = Tb, Dy) generated singlemolecule magnets with unusually high magnetic anisotropy barriers. [56] The homocoupling of terminal alkynes into trienediyl complexes by alkyl samarocenes as shown in Scheme 75 is experimentally well established. By means of computational techniques, the mechanism of this reaction has now been investigated in detail.…”

“…The DFT calculations showed that the exchange coupling between the two Ln ions for each complex is very weak, but the antiferromagnetic Ln-bpymcouplings are strong. Ab initio calculations showed that the effective energy barrier of the M a n u s c r i p t 56 Tb and Dy derivatives mainly comes from the contribution of a single Tb III or Dy III fragment, which is only about one third of a single Ln energy barrier. For the Ho and Er complexes, however, both of the two Ho III or Er III fragments contribute to the total energy barrier.…”