Magnetic Anisotropies in Rhombic Lanthanide(III) Complexes Do Not Conform to Bleaney’s Theory

Abstract

We report a complete set of magnetic susceptibilities of lanthanide complexes with a macrocyclic ligand based on a 3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane platform containing four hydroxyethyl pendant arms (L(1)). The [LnL(1)](3+) complexes are isostructural along the lanthanide series from Ce(3+) to Yb(3+), with the only structural change observed along the series being the monotonous shortening of the Ln-donor distances due to lanthanide contraction. The (1)H NMR spectra point to a D2 symmetry of the [LnL(1)](3+) complexes in aqueous solution, which provides a unique opportunity for analysis of the rhombic magnetic anisotropies with an unequivocal location of the magnetic axes. The contact contributions for the observed paramagnetic shifts have been estimated with density functional theory calculations on the [GdL(1)](3+) complex. Subsequently, the pseudocontact shifts could be factored out, thereby giving access to the axial and rhombic contributions of the magnetic susceptibility tensor. Our results show that the calculated magnetic anisotropies do not follow the trends predicted by Bleaney's theory, particularly in the case of Ho(3+) and Er(3+) complexes.

The Relationship between NMR Chemical Shifts of Thermally Polarized and Hyperpolarized 89Y Complexes and Their Solution Structures

“…[17][18][19][20][21][22][23][24][25] The X-ray structure obtainedu sing singlec rystals with formula [Y(P2C14Et4)](-NO 3 ) 3 ·6H 2 Oc onfirmt hat the [Y(P2C14Et4)] 3 + complex retains the ten-coordinate structure observed for the Ln 3 + series along the whole lanthanide series ( Figure 1). [20,25] Similarly,t he [Y(Me2DO2PA)] + and[ Y(CB-TE2PA)] + complexes adopt eightcoordinate structures in the solid state very similart ot hose establishedf or the corresponding complexes with the Ln 3 + ions (Figure 2a nd Figure 3). [18,19,21] The family of Y 3 + complexes with macrocyclic ligands investigated in thisw ork also includes…”

Local structure and magnetism of LaxEu1−xPO4Martel1, Rakhmatullin2, Baldoví3 et al. 2019Phys. Rev. B6030View full textAdd to dashboardCite

“…Unfortunately, due to its nonmagnetic ground state, the calculation of EPR parameters using DFT calculations for the Eu 3+ cation is not straightforward. However, a team of researchers [37][38][39] overcame this drawback by substituting this 4 f 6 cation by Gd 3+ (4 f 7 ). They multiplied the obtained A iso values by a factor of 0.34 and succeeded in predicting the paramagnetic shifts.…”

“…In order to account for the seven magnetically different environments; seven C1 clusters were implemented substituting each time a different La 3+ atom TABLE V. Isotropic hyperfine coupling constants (A iso /h, MHz) and shifts due to the Fermi contact interaction (δ FC , ppm) calculated based on the P 1 La 6 Gd 1 O 25 H 21 (C1) and Gd 1 P 7 La 11 O H 11 (C2) clusters. As suggested previously [37][38][39], the A iso /h values determined from the Gd 3+ clusters were scaled by a factor of 0.34 in order to predict the ones expected for an Eu 3+ cluster. by a Gd 3+ atom.…”

“…The determination of these paramagnetic shifts (δ p ) is currently based on a combination of empirical calculations using the Bleaney's theory for δ PC [26,27] and the McConnell and Robertson approach and its recent improvements for δ FC [28][29][30][31][32][33][34]. The theoretical prediction of paramagnetic shifts in the rare-earth series is intensively studied [24,35,36] especially for MRI contrast agents [37][38][39][40][41][42][43][44] and in metalloproteins [45][46][47][48]. However, these experiments are mostly performed using liquid-state NMR on organic molecules, usually containing conveniently one isolated paramagnetic cation.…”

Probing the Local Magnetic Structure of the [FeIII(Tp)(CN)3]− Building Block Via Solid‐State NMR Spectroscopy, Polarized Neutron Diffraction, and First‐Principle Calculations

“…The rationalization of these macroscopic magnetic properties is then commonlya ddressed by phenomenological approaches based on spin Hamiltonian models. Examples can be found for numerous kinds of paramagnetics ystems, including lanthanide-based compounds, [24][25][26] or solid-state materials [27] such as lithium ion batteries. However,the analysis of the EPR data relies on effective Hamiltonian (g-tensors and/ or zero-field splitting parameters).…”