Single-Ion Anisotropy and Intramolecular Interactions in Ce^III and Nd^III Dimers

Abstract

This article reports the syntheses, characterization, structural description, together with magnetic and spectroscopic properties of two isostructural molecular magnets based on the chiral ligand N , N ′- bis ((1,2-diphenyl-(pyridine-2-yl)methylene)-( R , R / S , S )-ethane-1,2-diamine), L1 , of general formula [Ln 2 ( RR - L1 ) 2 (Cl 6 )] · MeOH · 1.5H 2 O, (Ln = Ce ( 1 ) or Nd ( 2 )). Multifrequency electron paramagnetic resonance (EPR), cantilever torque magnetometry (CTM) measurements, and ab initio calculations allowed us to determine single-ion magnetic anisotropy and intramolecular magnetic interactions in both compounds, evidencing a more important role of the anisotropic exchange for the Nd III derivative. The comparison of experimental and theoretical data indicates that, in the case of largely rhombic lanthanide ions, ab initio calculations can fail in determining the orientation of the weakest components, while being reliable in determining their principal values. However, they remain of paramount importance to set the analysis of EPR and CTM on sound basis, thus obtaining a very precise picture of the magnetic interactions in these systems. Finally, the electronic structure of the two complexes, as obtained by this approach, is consistent with the absence of zero-field slow relaxation observed in ac susceptibility.

Field-induced mononuclear cobalt(ii) single-molecule magnet (SMM) based on a benzothiadiazole-ortho-vanillin ligand

“…Firstly, this spectrum roughly shows the same splitting of the signals associated with g y and g z from the Q-band EPR spectrum, leaving no doubt about the presence of an intermolecular electron-electron coupling. 64 Additionally, a split signal in the region from 10 to 13 kG is associated with a tiny g x value of 0.55, in agreement with the previous conclusions. In summary, the EPR study allows us to establish a negative sign of D, a high rhombicity or E/D ratio, and the presence of intermolecular magnetic interactions between close neighbours.…”

“…Since both centres were assumed collinear, only an anisotropic spin-spin coupling may split the signals in the Q-band EPR spectrum. 64 The spin Hamiltonian that considers this coupling is summarized by eqn (4)…”

Electronic structure comparisons of isostructural early d- and f-block metal(iii) bis(cyclopentadienyl) silanide complexes

“…proposed by Antiñolo et al 66 SQUID magnetometry and EPR spectra of 2-Ce, 2-Nd and 2-U showed extensive exchange interactions between the metal ions; these data are challenging to model, 67 and will be communicated in a separate publication as they are outside the main focus of this study. arises from crystal field splitting of the lowest total angular momentum multiplet.…”

“…2). A solution of 2-Zr in C 6 D 6 at 300 K was found to be paramagnetic by the Evans method, but less than expected for two uncoupled S = 1/2 (0.26 compared to 0.75 cm 3 K mol −1 ), indicating weaker antiferromagnetic coupling than in the solid state, some minor sample decomposition, and/or the presence of some monomeric [Zr(Cp ′′ ) 2 Cl] (1-Zr) in solution as proposed by Antiñolo et al 65 SQUID magnetometry and EPR spectra of 2-Ce, 2-Nd and 2-U showed extensive exchange interactions between the metal ions; these data are challenging to model, 66 and will be communicated in a separate publication as they are outside the main focus of this study. Complexes 3-Ce and 3-Nd are more strongly magnetic than 3-Ti and 3-Zr due to the presence of orbital angular momentum; the smooth decrease in c M T with reducing temperature arises from crystal eld splitting of the lowest total angular momentum multiplet.…”

Isolation and redox reactivity of cerium complexes in four redox states

“…Similar rhombic EPR spectra were previously reported for Ce(III) complexes. 20 Overall the EPR spectrum of 5 seems to point toward the presence of a Ce(III) component. However, the EPR spectrum is very different aer the addition of cryptands showing only a very weak and broad signal and a strong radical signal at g = 2.0054 (Scheme S2, † Fig.…”