DFT Investigations of the Magnetic Properties of Actinide Complexes

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, 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.

Electronic structure and magnetic properties of naphthalene- and stilbene-diimide-bridged diuranium(V) complexes: a theoretical study

“…[1][2][3][4][5][6][7][8][9][10] Indeed, their ability to support exotic metal−ligand bonding motifs, large spin-orbit coupling and anisotropy barriers allows potential applications in the field of single-molecule magnets (SMM), as pointed out in several recent reviews. [1][2][3][4][5][6][11][12][13][14] In particular, the unique features of actinide-containing molecules may be exploited for the design and synthesis of new binuclear actinide systems exhibiting magnetic coupling interactions. [15][16][17] Moreover, the more diffuse f orbitals in actinide compared to lanthanide ions 8,18 may lead to stronger magnetic superexchange.…”

“…5,6,8,[19][20][21] Despite the growing number of various synthesized actinide-containing complexes, the theoretical study of their magnetic behavior remains a challenge for quantum chemistry. 1,5,6,9,10 If significant progress has been made in the computation of magnetic coupling constants in bridged transition metal systems 22,23 the magnetic properties of actinide complexes were investigated by quantum chemistry methods in only a few studies. 9,10,24,25 Density Functional Theory (DFT) in combination with the hybrid B3LYP functional 26,27 and the Broken-Symmetry (BS) approach, 28,29 was successfully used to explore the electronic structure of actinide-containing molecules and compute their magnetic exchange coupling.…”

“…9,10,24,25 Density Functional Theory (DFT) in combination with the hybrid B3LYP functional 26,27 and the Broken-Symmetry (BS) approach, 28,29 was successfully used to explore the electronic structure of actinide-containing molecules and compute their magnetic exchange coupling. 1,19,30 − 35 Such theoretical approaches could be viewed as useful tools for the design of new actinide bearing compounds with strong magnetic exchange coupling.…”

“…The first binuclear magnetic actinide system was reported in the 1990s by Rosen et al 36 These authors found that the diuranium(V) phenyl-diimide para-bridged [(MeC 5 H 4 ) 3 U] 2 (µ-1,4-N 2 C 6 H 4 ) complex shows antiferromagnetic (AF) 5f 1 -5f 1 exchange coupling (J = −19 cm −1 ). Afterwards, a growing number of compounds exhibiting unusual U(V)-U(V) couplings have been synthetized, including pentavalent uranium dimers, dioxo-bridged compounds and few examples of diuranium(III), diuranium(IV) and mixed uranium(IV)-transition metal complexes are also known, as recently reviewed (see references herein).…”

“…Afterwards, a growing number of compounds exhibiting unusual U(V)-U(V) couplings have been synthetized, including pentavalent uranium dimers, dioxo-bridged compounds and few examples of diuranium(III), diuranium(IV) and mixed uranium(IV)-transition metal complexes are also known, as recently reviewed (see references herein). 1,11 Herein, we report a theoretical investigation of two bridged diuranium(V) diimide complexes, i.e. By studying such systems, using DFT computations coupled to the BS recipe, we aim at assessing the nature and strength of the exchange coupling by drawing magneto-structural correlations between the two models [Cp 3 U V ] 2 (µ-L) (L = stilbene-and naphthalene-diimide).…”