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 [Ln2(RR-L1)2(Cl6)]·MeOH·1.5H2O, (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 NdIII 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.
Highlights
The discovery by Ishikawa and co-workers[1] of slow magnetic relaxation in terbium-phthalocyaninate provoked a growing interest in the use of lanthanide complexes as single molecule magnets (SMMs)[2−6] and, more recently, for quantum information processing (QIP).[7−10] The interesting magnetic behavior of these complexes benefits from their large unquenched orbital angular moments, resulting from strong spin−orbit coupling and weak ligand fields, which impart strong magnetic anisotropy
Scheme 1 environment can be obtained for the larger lanthanides, whereas monomeric complexes with formula [Ln(L1)Cl3] and LnN4Cl3 heptacoordination were previously reported for the smaller ones.[37]
They are far from being perfect and use of the results obtained by this method requires a preliminary benchmarking against a set of accurately determined properties.[17]. This approach is gaining increasing momentum in the literature: the calculated properties include low-temperature luminescence,[48,49] electron paramagnetic resonance (EPR) spectroscopy,[13,50,51] single-crystal magnetometry,[15,52−54] inelastic neutron scattering,[55,56] and advanced spectroscopic techniques.[57−59] With this aim, ab initio calculations were performed on 1 and 2, and the results are compared with EPR
Summary
The discovery by Ishikawa and co-workers[1] of slow magnetic relaxation in terbium-phthalocyaninate provoked a growing interest in the use of lanthanide complexes as single molecule magnets (SMMs)[2−6] and, more recently, for quantum information processing (QIP).[7−10] The interesting magnetic behavior of these complexes benefits from their large unquenched orbital angular moments, resulting from strong spin−orbit coupling and weak ligand fields, which impart strong magnetic anisotropy Looking forward to these ambitious applications, it is important to understand all the possible variables that can play a relevant role in determining the dynamic magnetic properties of these molecular systems. The surroundings of the qubits must be chosen with care, since the presence of any other spin provides a Received: March 3, 2021 Published: June 10, 2021
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