Characterization of berkelium(III) dipicolinate and borate compounds in solution and the solid state

Abstract

Berkelium is positioned at a crucial location in the actinide series between the inherently stable half-filled 5f(7) configuration of curium and the abrupt transition in chemical behavior created by the onset of a metastable divalent state that starts at californium. However, the mere 320-day half-life of berkelium's only available isotope, (249)Bk, has hindered in-depth studies of the element's coordination chemistry. Herein, we report the synthesis and detailed solid-state and solution-phase characterization of a berkelium coordination complex, Bk(III)tris(dipicolinate), as well as a chemically distinct Bk(III) borate material for comparison. We demonstrate that berkelium's complexation is analogous to that of californium. However, from a range of spectroscopic techniques and quantum mechanical calculations, it is clear that spin-orbit coupling contributes significantly to berkelium's multiconfigurational ground state.

CONDON 3.0: An Updated Software Package for Magnetochemical Analysis‐All the Way to Polynuclear Actinide Complexes

“…The mononuclear 5 f 8 actinide coordination compound Bk III (HDPA) 3 ·H 2 O was recently reported by M. A. Silver et al, along with the first magnetochemical characterization of a trans‐uranium compound based on a “full model.” The peculiarity of this example concerns the elucidation of the electronic structure of actinide coordination compounds. Such insight will also provide a better comprehensive understanding of later actinides.…”

“…To emphasize the subtleties in the various approaches to model exchange‐coupled actinide systems, the basics are briefly recapitulated. From a computational point of view, most of the essential information has been given in multiple works concerning mononuclear and polynuclear 5 f ‐electron systems …”

Measurements related to the magnetism of curium metal

“…Our own experience described in this paper illustrates this aspect. On the other hand, the appearance of a second rare-earth-like series of elements starting at Am and extending to the end of the 5 f series is frequently quoted, but has recently been challenged by a series of experiments on the chemistry of transplutonium compounds [9,10]. This recent discussion, as well as the fact that we describe work on an element, makes it important to document our work, even if the conclusions are not as clear as we would like.…”

Transuranic Computational Chemistry

“…Silver et al developed new experimental techniques to study the berkelium analogues of the californium systems discussed above, that is, Bk[B 6 O 8 (OH) 5 ]a nd Bk(HDPA) 3 ·H 2 O. [32] Although the geometric structure of the former indicates that Bk III is more similar to Cf III than the earlier actinides (it is 8-coordinate), the electronic structure is more akin to its predecessors than to Cf III ;l igand field splittings can be an order of magnitude larger in Cf III than Bk III .S trong evidence for this comesf rom the measured magnetic properties of Bk[B 6 O 8 (OH) 5 ]a nd Bk(HDPA) 3 ·H 2 O, and calculation of the latter at the CASSCF-SO level.T hese calculations find that the ground and lowest excited states derive from the effects of SOC on the free Bk 3 + 7 F 6 and 5 G 6 levels (the latter being a minor (17 %) contributor)). The magnetic susceptibility calculated from this electronic structure is in reasonable agreement with experiment, leading to the conclusion that for the 5f shell, ligand fielde ffects are secondary to SOC.…”