Characterizing how actinide properties change across the f-element series is critical for improving predictive capabilities and solving many nuclear problems facing our society. Unfortunately, it is difficult to make direct comparisons across the 5f-element series because so little is known about trans-plutonium elements. Results described herein help to address this issue through isolation of An(S2CNEt2)3(N2C12H8) (Am, Cm, and Cf). These findings included the first single crystal X-ray diffraction measurements of Cm-S (mean of 2.86 ± 0.04 Å) and Cf-S (mean of 2.84 ± 0.04 Å) bond distances. Furthermore, they highlight the potential of An(S2CNEt2)3(N2C12H8) for providing a test bed for comparative analyses of actinide versus lanthanide bonding interactions.

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Covalency is often considered to be an influential factor in driving An3+ vs. Ln3+ selectivity invoked by soft donor ligands. This is intensely debated, particularly the extent to which An3+/Ln3+ covalency differences prevail and manifest as the f‐block is traversed, and the effects of periodic breaks beyond Pu. Herein, two Am complexes, [Am{N(E=PPh2)2}3] (1‐Am, E=Se; 2‐Am, E=O) are compared to isoradial [Nd{N(E=PPh2)2}3] (1‐Nd, 2‐Nd) complexes. Covalent contributions are assessed and compared to U/La and Pu/Ce analogues. Through ab initio calculations grounded in UV‐vis‐NIR spectroscopy and single‐crystal X‐ray structures, we observe differences in f orbital involvement between Am–Se and Nd–Se bonds, which are not present in O‐donor congeners.

M(EtBTP) 3 ][BPh 4 ] 3 ·3CH 3 CN (M = Nd, Am;EtBTP = 2,6-bis(5,6-diethyl-1,2,4-triazin-3-yl)pyridine) have been synthesized from reactions of MCl 3 ·n H 2 Ow ith EtBTP in acetonitrile followed by anion metathesis. Structural analysis reveals that these compounds contain M 3 + cations bound by tridentate EtBTP ligands to create at ricapped trigonal prismatic geometry around the metal centers. Collection of high-resolution,s ingle-crystal X-ray diffraction data also allowedr eductioni nb ond lengths esd's, such that as light contraction of D = 0.0158(18) in the AmÀNv ersus NdÀNb ond lengths waso bserved, even thought hese cationso stensibly have matchingi onic radii. Theoretical evaluation revealed enhanced metal-ligand bondingt hroughb ack donation in the [Am(EtBTP) 3 ] 3 + complex that is absentin[Nd(EtBTP) 3 ] 3 + .The importance of separating Am III from Ln III (Ln = lanthanide) cations stems from the need for more sensible ande fficient nuclear fuel cycles. The recycling of used nuclear fuel centers on the extraction of reusable uranium and plutonium through PUREX-like processes, and their re-use as mixed-oxide(MOX) nuclear fuels. [1] However,s toring the remaining waste after this extractioni sn on-trivial, because it is composed of fissionproducts, such as 90 Sr, 137 Cs, and lanthanides, as wella st he socalled minor actinides, neptunium, americium, and curium;t he latter actinides formed via neutron capture. After extraction of uranium and plutonium, the bulk of the waste consists of either stable isotopes or ones with relativelys hort half-lives, with notable long-lived exceptions that include 99 Tc (t1 = 2 = 2.11 10 5 years)a nd 135 Cs (t1 = 2 = 2.3 10 6 years).In contrast, americium is mostly presenti nt he form of 241 Am, which possesses an intermediate half-life of 432.2 years. Neutron capture and b decay processes primarily from the parenti sotope 241 Pu create > 1.3 kg of americium per ton of typical used nuclear fuel. [2] Thus, the term "minora ctinide" is inappropriate for americium and probably needs to be discard-ed in its entirety. Arguments can be made that it represents an energyr esourcef or fast neutron reactors, in which it can be fissioned, andt hat its removal from nuclear waste dramatically decreases the long-term radioactivity of ar epository.H owever, the primary driving force justifying its extraction is the heat load that it createsi nn uclear repository scenarios. Accordingly, separating americium from post-PUREX nuclear waste streams has becomeafocal point of radiochemicalinterest.Nitrogen-donor ligands, in contrastt ot raditional oxygen donors, such as phosphonates and organophosphates, have been the subjecto fi ncreased attention over the past several decades because of their potential use in f-block separations. These complexes possess the addedb enefito fi ncineration leadings olely to the formation of actinideo xides, thereby reducingt he volumeo fr adioactive waste in repositories. One particularly promising family of ligands that falls into this class are the tridentate, nit...

In this study, the synthesis, characterization, and pressure response of a 1D californium mellitate (mellitate = 1,2,3,4,5,6-benzenehexacarboxylate) coordination polymer, Cf2(mell)­(H2O)10·4H2O (Cf-1), are reported. The Cf–O lengths within the crystal structure are compared to its gadolinium (Gd-1) and holmium (Ho-1) analogs as well. These data show that the average Cf–O bond distance is slightly longer than the average Gd–O bond, consistent with trends in effective ionic radii. UV–vis-NIR absorption spectra as a function of pressure were collected using diamond-anvil techniques for both Cf-1 and Ho-1. These experiments show that the Cf­(III) f → f transitions have a stronger dependence on pressure than that of the holmium analog. In the former case, the shift is nearly linear with applied pressure and averages 6.6 cm–1/GPa, whereas in the latter, it is <3 cm–1/GPa.

Radical cyclization reactions at a peri position were used for the synthesis of polyaromatic compounds. Depending on the choice of reaction conditions and substrate, this flexible approach led to Bu Sn-substituted phenalene, benzanthrene, and olympicene derivatives. Subsequent reactions with electrophiles provided synthetic access to previously inaccessible functionalized polyaromatic compounds.

Efforts to quantitatively reduce CfIII → CfII in solution as well as studies of its cyclic voltammetry have been hindered by its scarcity, significant challenges associated with manipulating an unusually intense γ emitter, small reaction scales, the need for nonaqueous solvents, and its radiolytic effects on ligands and solvents. In an effort to overcome these impediments, we report on the stabilization of CfII by encapsulation in 2.2.2-cryptand and comparisons with the readily reducible lanthanides, Sm3+, Eu3+, and Yb3+. Cyclic voltammetry measurements suggest that CfIII/II displays electrochemical behavior with characteristics of both SmIII/II and YbIII/II. The °E 1/2 values of −1.525 and −1.660 V (vs Fc/Fc+ in tetrahydrofuran (THF)) for [Cf­(2.2.2-crypt)]3+/2+ and [Sm­(2.2.2-crypt)]3+/2+, respectively, are similar. However, the ΔE values upon complexation by 2.2.2-cryptand for CfIII/II more closely parallels YbIII/II with postencapsulation shifts of 705 and 715 mV, respectively, whereas the shift of SmIII/II (520 mV) mirrors that of EuIII/II (524 mV). This suggests more structural similarities between CfII and YbII in solution than with SmII that likely originates from more similar ionic radii and local coordination environments, a supposition that is corroborated by crystallographic and extended X-ray absorption fine structure measurements from other systems. Competitive-ion binding experiments between EuIII/II, SmIII/II, and YbIII/II were also performed and show less favorable binding by YbIII/II. Connectivity structures of [Ln­(2.2.2-cryptand)­(THF)]­[BPh4]2 (Ln = EuII, SmII) are reported to show the important role that THF plays in these redox reactions.

M(TpyNO 2 )(NO 3 ) 3 (H 2 O)•THF (M = La, Nd, Sm, Eu, Tb, Am; TpyNO 2 = 4′-nitrophenyl terpyridyl) have been prepared from the reaction of M(NO 3 ) 3 •nH 2 O with TpyNO 2 in THF. Structural analysis shows that the metal centers are 10-coordinate, providing the first example of Am III with this coordination number. Further spectroscopic and theoretical evaluation of these complexes reveals utilization of the 5f orbitals in bonding in the Am III complex. Comparison of Nd−L, Eu−L, and Am−L bond distances demonstrates that some caution should be taken in comparing Eu III versus Am III in extraction experiments.