Magnetic Properties of Complexes of Actinide Elements

A special issue of Magnetochemistry (ISSN 2312-7481).

Deadline for manuscript submissions: closed (31 March 2019) | Viewed by 12418

Special Issue Editor


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Guest Editor
Laboratoire de Chimie et Physique Quantiques, Université Toulouse III, 118 route de Narbonne, 31062 Toulouse, France
Interests: magnetic properties of lanthanide and actinide complexes; theoretical description of EPR parameters; magnetic susceptibility and magnetic coupling; pNMR shifts

Special Issue Information

Dear Colleagues,

Magnetic properties of actinide complexes are borne by 5f open shell orbitals. These orbitals have a marked inner shell character, as in lanthanides, but interact more with the chemical environment than the 4f of lanthanides, leading to unique magnetic properties.

While a great deal of effort has been devoted, in the last few years, to analyze the degree of covalency in actinide complexes, less is known about their magnetic properties; because experimental data are quite scarce due to the radioactivity of the transuranium elements which requires specially equipped facilities and because spin-orbit effects are large and the covalency important making the interpretation of those properties rather difficult.

 The magnetic properties of actinide complexes may be approached using very different spectroscopic techniques, which provide complementary information. With this Special Issue of magnetochemistry, we aim to gather chemists and physicists, experimentalists and theoreticians, in order to make an overview of the state-of-the-art of this domain, joining the different perspectives, from the synthesis of new molecular architectures to the characterization and modelization of the properties.

This Special Issue aims to collect mini-reviews on the following domains, presenting a brief state of the art, outlining the specificities of magnetic properties of actinide as compared to the lanthanides and transition metals, and concluding with some perspectives.

  • Synthesis and characterization of actinide based Single Molecule Magnets and magnetic complexes.
  • Magnetic coupling between actinide and another magnetic center
  • Spectroscopies as a probe of magnetic properties of actinides: EPR, pNMR, MCD, XAS, XANES, XPS, etc.
  • Theoretical approaches for magnetic properties of actinide complexes.

Dr. Hélène Bolvin
Guest Editor

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Published Papers (2 papers)

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Research

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28 pages, 3403 KiB  
Article
Modelling the Effect of Zero-Field Splitting on the 1H, 13C and 29Si Chemical Shifts of Lanthanide and Actinide Compounds
by Austin W. Lloyd, Helen M. Moylan and Joseph J. W. McDouall
Magnetochemistry 2019, 5(1), 3; https://doi.org/10.3390/magnetochemistry5010003 - 11 Jan 2019
Cited by 1 | Viewed by 3391
Abstract
The prediction of paramagnetic NMR (pNMR) chemical shifts in molecules containing heavy atoms presents a significant challenge to computational quantum chemistry. The importance of meeting this challenge lies in the central role that NMR plays in the structural characterisation of chemical systems. Hence [...] Read more.
The prediction of paramagnetic NMR (pNMR) chemical shifts in molecules containing heavy atoms presents a significant challenge to computational quantum chemistry. The importance of meeting this challenge lies in the central role that NMR plays in the structural characterisation of chemical systems. Hence there is a need for reliable assignment and prediction of chemical shifts. In a previous study [Trends in Physical Chemistry, 17, 25–57, (2017)] we looked at the computation of pNMR chemical shifts in lanthanide and actinide complexes using a spin Hamiltonian approach. In that study we were principally concerned with molecules with S = 1/2 ground states. In the present work we extend that study by looking at the effect of zero field splitting (ZFS) for six complexes with S = 3/2 ground states. It is shown that the inclusion of ZFS can produce substantial shifts in the predicted chemical shifts. The computations presented are typically sufficient to enable assignment of experimental spectra. However for one case, in which the peaks are closely clustered, the inclusion of ZFS re-orders the chemical shifts making assignment quite difficult. We also observe, and echo, the previously reported importance of including the paramagnetic spin-orbit hyperfine interaction for 13 C and 29 Si atoms, when these are directly bound to a heavy element and thus subject to heavy-atom-light-atom effects. The necessary computations are very demanding, and more work is needed to find theoretical and computational approaches that simplify the evaluation of this term. We discuss the computation of each term required in the spin Hamiltonian. The systems we study in this work are restricted to a single heavy atom ion (one Nd(III) and five U(III) complexes), but typify some of the computational complexity encountered in lanthanide and actinide containing molecules. Full article
(This article belongs to the Special Issue Magnetic Properties of Complexes of Actinide Elements)
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Review

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31 pages, 10370 KiB  
Review
DFT Investigations of the Magnetic Properties of Actinide Complexes
by Lotfi Belkhiri, Boris Le Guennic and Abdou Boucekkine
Magnetochemistry 2019, 5(1), 15; https://doi.org/10.3390/magnetochemistry5010015 - 17 Feb 2019
Cited by 13 | Viewed by 5326
Abstract
Over the past 25 years, magnetic actinide complexes have been the object of considerable attention, not only at the experimental level, but also at the theoretical one. Such systems are of great interest, owing to the well-known larger spin–orbit coupling for actinide ions, [...] Read more.
Over the past 25 years, magnetic actinide complexes have been the object of considerable attention, not only at the experimental level, but also at the theoretical one. Such systems are of great interest, owing to the well-known larger spin–orbit coupling for actinide ions, and could exhibit slow relaxation of the magnetization, arising from a large anisotropy barrier, and magnetic hysteresis of purely molecular origin below a given blocking temperature. Furthermore, more diffuse 5f orbitals than lanthanide 4f ones (more covalency) could lead to stronger magnetic super-exchange. On the other hand, the extraordinary experimental challenges of actinide complexes chemistry, because of their rarity and toxicity, afford computational chemistry a particularly valuable role. However, for such a purpose, the use of a multiconfigurational post-Hartree-Fock approach is required, but such an approach is computationally demanding for polymetallic systems—notably for actinide ones—and usually simplified models are considered instead of the actual systems. Thus, Density Functional Theory (DFT) appears as an alternative tool to compute magnetic exchange coupling and to explore the electronic structure and magnetic properties of actinide-containing molecules, especially when the considered systems are very large. In this paper, relevant achievements regarding DFT investigations of the magnetic properties of actinide complexes are surveyed, with particular emphasis on some representative examples that illustrate the subject, including actinides in Single Molecular Magnets (SMMs) and systems featuring metal-metal super-exchange coupling interactions. Examples are drawn from studies that are either entirely computational or are combined experimental/computational investigations in which the latter play a significant role. Full article
(This article belongs to the Special Issue Magnetic Properties of Complexes of Actinide Elements)
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