Theoretical Investigation of Single-Molecule-Magnet Behavior in Mononuclear Dysprosium and Californium Complexes

Abstract

Early-actinide-based (U, Np, and Pu) single-molecule magnets (SMMs) have yet to show magnetic properties similar to those of highly anisotropic lanthanide-based ones. However, there are not many studies exploring the late-actinides (more than half-filled f shells) as potential candidates for SMM applications. We computationally explored the electronic structure and magnetic properties of a hypothetical Cf­(III) complex isostructural to the experimentally synthesized Dy­(dbm)3(bpy) complex (bpy = 2,2′-bipyridine; dbm = dibenzoylmethanoate) via multireference methods and compared them to those of the Dy­(III) analogue. This study shows that the Cf­(III) complex can behave as a SMM and has a greater magnetic susceptibility compared to other experimentally and computationally studied early-actinide-based (U, Np, and Pu) magnetic complexes. However, Cf spontaneously undergoes α-decay and converts to Cm. Thus, we also explored the isostructural Cm­(III)-based complex. The computed magnetic susceptibility and g-tensor values show that the Cm­(III) complex has poor SMM behavior in comparison to both the Dy­(III) and Cf­(III) complexes, suggesting that the performance of Cf­(III)-based magnets may be affected by α-decay and can explain the poor performance of experimentally studied Cf­(III)-based molecular magnets in the literature. Further, this study suggests that the ligand field is dominant in Cf­(III), which helps to increase the magnetization blocking barrier by nearly 3 times that of its 4f congener.

Actinide-based single-molecule magnets: alone or in a group?

“…Just this year, the Gagliardi group theoretically investigated the electronic structure and SMM behaviours of californium( iii ) complex Cf(dbm) 3 (bpy) (bpy = 2,2′-bipyridine; dbm = dibenzoylmethanoate). 60 This study shows that the computed energy barrier of the 5f 9 complex is higher than that of the Dy( iii ) analogue due to the stronger spin–orbit coupling and crystal field splitting. Then, a linear L–Cf( iii )–L complex might show promising performance, however, the scarcity and instability limit experimental studies.…”

Triggering single-molecule qubit spin dynamics via non-Abelian geometric phase effects

“…While we have focused on the specific examples of CoCl 2 (tu) 4 and TbPc 2 single-molecule magnets, there are a myriad of alternative candidate molecules reported in the literature which may also show these effects. For example, the tunnel split |J = 8, m J = AE8i ground doublet of a recently reported Ho 3 + singlemolecule magnet synthesised and characterised by Wu et al 50 In that study, a tunnel splitting of 10 À5 cm À1 was obtained from ab initio calculations suggesting that rotations should be carried out on ms timescales to observe the above non-adiabatic rotationinduced spin dynamics of the tunnelling ground states.…”

“…In the first instance, the geometric propagator U square which takes the system around a closed square path on the unit sphere can, due to path-ordering, be decomposed into the ordered product of geometric propagators U (4) square U (3) square U (2) square U (1) square along each of the four legs (enumerated in Fig. 1) in which the system is rotated along constant lines of either latitude or longitude.…”

Multiconfiguration Pair-Density Functional Theory for Vertical Excitation Energies in Actinide Molecules

“…Actinides are present in nuclear and radioactive processes; therefore, understanding their electronic structure is very important. , Being able to accurately describe the behavior of f-electrons in computations, including strong correlation effects, spin–orbit coupling, and multiplet complexity, is a challenge. This is especially true because actinides possess a strong crystal field and spin–orbit coupling (SOC). − A multiconfiguration treatment, including SOC, is indispensable for calculations on actinides. Active-space self-consistent field calculations account for static correlation (near degeneracy effect) and are usually followed by a perturbative (second-order) treatment that recovers dynamic correlation, which is very important for actinide molecules to correctly describe metal–ligand covalency , because the 5f valence orbitals in actinides are diffused and hence exert a strong ligand field. − However, multireference second-order perturbation theory (MRPT2) methods are very expensive when the active space is large (e.g., beyond the 5f shell) and also when many electronic states are computed, using state average procedures. ,, …”