An electrostatic model for the determination of magnetic anisotropy in dysprosium complexes

Abstract

Understanding the anisotropic electronic structure of lanthanide complexes is important in areas as diverse as magnetic resonance imaging, luminescent cell labelling and quantum computing. Here we present an intuitive strategy based on a simple electrostatic method, capable of predicting the magnetic anisotropy of dysprosium(III) complexes, even in low symmetry. The strategy relies only on knowing the X-ray structure of the complex and the well-established observation that, in the absence of high symmetry, the ground state of dysprosium(III) is a doublet quantized along the anisotropy axis with an angular momentum quantum number m J ¼ ± 15 / 2 . The magnetic anisotropy axis of 14 low-symmetry monometallic dysprosium(III) complexes computed via high-level ab initio calculations are very well reproduced by our electrostatic model. Furthermore, we show that the magnetic anisotropy is equally well predicted in a selection of low-symmetry polymetallic complexes.

Direct measurement of dysprosium(III)˙˙˙dysprosium(III) interactions in a single-molecule magnet

“…1a). Electrostatic optimization of the oblate m J ¼ ± 15 / 2 electron density 24 provides the same result (8.6°difference to CASSCF) and confirms that this orientation is due to the short terminal Dy-O bond of 2.248(3) Å (c.f. 2.349(3)-2.384(3) Å for the bridging oxygen atoms), identical to the motif in the recently described homoleptic [Dy 3 (hq) 9 ] 25 .…”

Using the Singly Deprotonated Triethanolamine to Prepare Dinuclear Lanthanide(III) Complexes: Synthesis, Structural Characterization and Magnetic Studies

“…Following this method and the program MAGELLAN (a FORTRAN program), the ground state magnetic anisotropy axis for each Dy III ion (the two axis are co-parallel due to the existence of the crystallographically imposed inversion center in the molecule) is directed towards the bridging oxygen atoms O1/O1 (Figure 8), which exhibit the shortest Dy-O bond distances (Table 2). This forces the oblate electron density of Dy III to be almost parallel to the easy axis, which is a non-favorable spatial conformation to achieve slow relaxation of the magnetization [52]. No frequency dependent out-of-phase ac magnetic susceptibility signals were observed for 3-5 under external dc fields of 0.1 and 0.2 T, suggesting that the complexes are not field-induced SMMs.…”

“…(Table 2). This forces the oblate electron density of Dy III to be almost parallel to the easy axis, which is a non-favorable spatial conformation to achieve slow relaxation of the magnetization [52]. …”

“…Therefore, to maximize the anisotropy of an oblate ion (and thus the chances to observe SMM properties), we should place it in a crystal field for which the ligand electron density is concentrated above and below the xy plane; this is clearly not the case here. Given that in the absence of high symmetry (as in 4), the ground state of Dy III is a doublet along the anisotropy axis with an angular momentum quantum number mj = ±15/2, we have determined the orientation of the ground state magnetic anisotropy axis for the Dy III center of 4 using a method reported in 2013 [52], based on an electrostatic model. This method does not demand the fitting of experimental data; it only requires the knowledge of the single-crystal X-ray structure of the complex.…”

4f occupancy and magnetism of rare-earth atoms adsorbed on metal substrates

“…The CF potential, which is given by the position and strength of such point charges, is a measure of RE-substrate interaction. In particular, this approach is best suited for the 4f states as their highly localized character reduces the interaction of the REs with the surrounding atoms to a purely electrostatic nature [14,[58][59][60]. Moreover, Er is the ideal prototype for this analysis since it exhibits different occupancies on the two crystallographic faces of Ag and this further allows us to gain insight into the effects of CF and coordination.…”