Construction of a General Library for the Rational Design of Nanomagnets and Spin Qubits Based on Mononuclear f‑Block Complexes. The Polyoxometalate Case

This paper belongs to a series of
contributions aiming at establishing
a general library that helps in the description of the crystal field
(CF) effect of any ligand on the splitting of the J ground states
of mononuclear f-element complexes. Here, the effective parameters
associated with the oxo ligands (effective charges and metal–ligand
distances) are extracted from the study of the magnetic properties
of the first two families of single-ion magnets based on lanthanoid
polyoxometalates (POMs), formulated as [Ln­(W5O18)2]9– and [Ln­(β2-SiW11O39)2]13– (Ln = Tb,
Dy, Ho, Er, Tm, Yb). This effective CF approach provides a good description
of the lowest-lying magnetic levels and the associated wave functions
of the studied systems, which is fully consistent with the observed
magnetic behavior. In order to demonstrate the predictive character
of this model, we have extended our model in a first step to calculate
the properties of the POM complexes of the early 4f-block metals.
In doing so, [Nd­(W5O18)2]9– has been identified as a suitable candidate to exhibit SMM behavior.
Magnetic experiments have confirmed such a prediction, demonstrating
the usefulness of this strategy for the directed synthesis of new
nanomagnets. Thus, with an effective barrier of 51.4 cm–1 under an applied dc field of 1000 Oe, this is the second example
of a Nd3+-based single-ion magnet.