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Antonietta M Lillo,1 Nileena Velappan,1 Julia M Kelliher,1 Austin J Watts,1 Samuel P Merriman,1 Grace Vuyisich,2 Laura M Lilley,2 Kent E Coombs,1 Tara Mastren,2 Munehiro Teshima,1 Benjamin W Stein,2 Gregory L Wagner,2 Srinivas Iyer,1 Andrew RM Bradbury,3 Jennifer Foster Harris,1 Armand E Dichosa,1 Stosh A Kozimor2 1Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM, USA; 2Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM, USA; 3Specifica Inc., Santa Fe, NM, USACorrespondence: Antonietta M LilloUSA Department of Energy, In Care of Los Alamos National Laboratory, Bikini Atoll Road, SM-30, TA-43, Building 0001, Room 220, Los Alamos, NM 87545, USATel +1 505-606-0578Fax +1 505-665-9030Email alillo@lanl.govBackground: Yersinia pestis is a category A infective agent that causes bubonic, septicemic, and pneumonic plague. Notably, the acquisition of antimicrobial or multidrug resistance through natural or purposed means qualifies Y. pestis as a potential biothreat agent. Therefore, high-quality antibodies designed for accurate and sensitive Y. pestis diagnostics, and therapeutics potentiating or replacing traditional antibiotics are of utmost need for national security and public health preparedness.Methods: Here, we describe a set of human monoclonal immunoglobulins (IgG1s) targeting Y. pestis fraction 1 (F1) antigen, previously derived from in vitro evolution of a phage-display library of single-chain antibodies (scFv). We extensively characterized these antibodies and their effect on bacterial and mammalian cells via: ELISA, flow cytometry, mass spectrometry, spectroscopy, and various metabolic assays.Results: Two of our anti-F1 IgG (αF1Ig 2 and αF1Ig 8) stood out for high production yield, specificity, and stability. These two antibodies were additionally attractive in that they displayed picomolar affinity, did not compete when binding Y. pestis, and retained immunoreactivity upon chemical derivatization. Most importantly, these antibodies detected < 1,000 Y. pestis cells in sandwich ELISA, did not harm respiratory epithelial cells, induced Y. pestis agglutination at low concentration (350 nM), and caused apparent reduction in cell growth when radiolabeled at a nonagglutinating concentration (34 nM).Conclusion: These antibodies are amenable to the development of accurate and sensitive diagnostics and immuno/radioimmunotherapeutics.Keywords: immunodiagnostic, radioimmunotherapy, RIT, immunotherapy, radiolabeling, immunoantibiotic, lateral flow assay, LFA

An investigation of the structural, thermodynamic, and electronic transport properties of the isoelectronic chemical substitution series Ce(Pd1-xNix)2P2 is reported, where a possible ferromagnetic quantum critical point is uncovered in the temperature-concentration (T-x) phase diagram. This behavior results from the simultaneous contraction of the unit cell volume, which tunes the relative strengths of the Kondo and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions, and the introduction of disorder through alloying. Near the critical region at xcr≈ 0.7, the rate of contraction of the unit cell volume strengthens, indicating that the cerium f valence crosses over from trivalent to a noninteger value. Consistent with this picture, x-ray absorption spectroscopy measurements reveal that while CePd2P2 has a purely trivalent cerium f state, CeNi2P2 has a small (

An investigation of the structural, thermodynamic, and electronic transport properties of the isoelectronic chemical substitution series Ce(Pd1-xNix)2P2 is reported, where a possible ferromagnetic quantum critical point is uncovered in the temperature-concentration (T-x) phase diagram. This behavior results from the simultaneous contraction of the unit cell volume, which tunes the relative strengths of the Kondo and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions, and the introduction of disorder through alloying. Near the critical region at xcr≈ 0.7, the rate of contraction of the unit cell volume strengthens, indicating that the cerium f valence crosses over from trivalent to a noninteger value. Consistent with this picture, x-ray absorption spectroscopy measurements reveal that while CePd2P2 has a purely trivalent cerium f state, CeNi2P2 has a small (

Recent advances enabled the discovery of heterometallic molecules for many metals: main group, d-block, lanthanides, and some actinides (U, Th). These complexes have at least two different metals joined by bridging ligands or by direct metal-metal bonding interactions. They are attractive because they can enable chemical cooperativity between metals from different parts of the periodic table. Some heterometallics provide access to unique reactivity and others exhibit physical properties that cannot be accessed by homometallic species. We envisioned that transuranic heterometallics might similarly enable new transuranic chemistry, though synthetic routes to such compounds have yet to be developed. Reported here is the first synthesis of a molecular transuranic complex that contains plutonium (Pu) and cobalt (Co). Our analyses of PuCl 3 {CoCp[OP(OEt) 2 ] 3 } showed Pu(iv) and Co(iii) were present and suggested that the Pu(iv) oxidation state was stabilized by the electron donating phosphite ligands. This synthetic method - and the demonstration that Pu(iv) can be stabilized in a heterobimetallic molecular setting - provides a foundation for further exploration of transuranic multimetallic chemistry., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Yersinia pestis, the causative agent of plague and a biological threat agent, presents an urgent need for novel medical countermeasures due to documented cases of naturally acquired antibiotic resistance and potential person-to-person spread during a pneumonic infection. Immunotherapy has been proposed as a way to circumvent current and future antibiotic resistance. Here, we describe the development and characterization of two affinity matured human antibodies (αF1Ig AM2 and αF1Ig AM8) that promote survival of mice after exposure to aerosolized Y. pestis. We share details of the error prone PCR and yeast display technology-based affinity maturation process that we used. The resultant matured antibodies have nanomolar affinity for Y. pestis F1 antigen, are produced in high yield, and are resilient to 37°C stress for up to 6 months. Importantly, in vitro assays using a murine macrophage cell line demonstrated that αF1Ig AM2 and αF1Ig AM8 are opsonic. Even more importantly, in vivo studies using pneumonic plague mouse models showed that 100% of the mice receiving 500 μg of IgGs αF1Ig AM2 and αF1Ig AM8 survived lethal challenge with aerosolized Y. pestis CO92. Combined, these results provide evidence of the quality and robustness of αF1Ig AM2 and αF1Ig AM8 and support their development as potential medical countermeasures against plague., Competing Interests: The authors have declared that no competing interests exist., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

Efficient catalytic protocols for C-H silylations of arenes and heteroarenes with sterically and electronically different hydrosiloxysilanes are disclosed. The silylations are catalyzed by a well-defined Rh-complex (1 mol%), derived from [Rh(1,5-hexadiene)Cl] 2 and a bulky BINAP type ligand. This catalyst not only promotes C-Si bond formation affording the desired products in up to 95% isolated yield, but also can suppress the silane redistribution side reactions of HSiMe 2 (OTMS). The protocol can also be applied for the C-H silylations of more reactive HSiMe(OTMS) 2 with a much lower catalyst loading (0.25 mol%) and even with sterically demanding HSi(OTMS) 3 . The steric bulk of the arene substituent and hydrosiloxysilane is a major factor in determining the regioselectivity and electronic effect as secondary. The current method can be performed under operationally diverse conditions: with/without a hydrogen scavenger or solvent., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Cerium-oxo clusters have applications in fields ranging from catalysis to electronics and also hold the potential to inform on aspects of actinide chemistry. Toward this end, a cerium-acetylacetonate (acac 1- ) monomeric molecule, Ce(acac) 4 ( Ce-1 ), and two acac 1- -decorated cerium-oxo clusters, [Ce 10 O 8 (acac) 14 (CH 3 O) 6 (CH 3 OH) 2 ]·10.5MeOH ( Ce-10 ) and [Ce 12 O 12 (OH) 4 (acac) 16 (CH 3 COO) 2 ]·6(CH 3 CN) ( Ce-12 ), were prepared and structurally characterized. The Ce(acac) 4 monomer contains Ce IV . Crystallographic data and bond valence summation values for the Ce-10 and Ce-12 clusters are consistent with both clusters having a mixture of Ce III and Ce IV cations. Ce L 3 -edge X-ray absorption spectroscopy, performed on Ce-10 , showed contributions from both Ce III and Ce IV . The Ce-10 cluster is built from a hexameric cluster, with six Ce IV sites, that is capped by two dimeric Ce III units. By comparison, Ce-12 , which formed upon dissolution of Ce-10 in acetonitrile, consists of a central decamer built from edge sharing Ce IV hexameric units, and two monomeric Ce III sites that are bound on the outer corners of the inner Ce 10 core. Electrospray ionization mass spectrometry data for solutions prepared by dissolving Ce-10 in acetonitrile showed that the major ions could be attributed to Ce 10 clusters that differed primarily in the number of acac 1- , OH 1- , MeO 1- , and O 2- ligands. Small angle X-ray scattering measurements for Ce-10 dissolved in acetonitrile showed structural units slightly larger than either Ce 10 or Ce 12 in solution, likely due to aggregation. Taken together, these results suggest that the acetylacetonate supported clusters can support diverse solution-phase speciation in organic solutions that could lead to stabilization of higher order cerium containing clusters, such as cluster sizes that are greater than the Ce 10 and Ce 12 reported herein.

Organoplutonium chemistry was established in 1965, yet structurally authenticated plutonium-carbon bonds remain rare being limited to π-bonded carbocycle and σ-bonded isonitrile and hydrocarbyl derivatives. Thus, plutonium-carbenes, including alkylidenes and N-heterocyclic carbenes (NHCs), are unknown. Here, we report the preparation and characterization of the diphosphoniomethanide-plutonium complex [Pu(BIPM TMS H)(I)(μ-I)] 2 ( 1Pu , BIPM TMS H = (Me 3 SiNPPh 2 ) 2 CH) and the diphosphonioalkylidene-plutonium complexes [Pu(BIPM TMS )(I)(DME)] ( 2Pu , BIPM TMS = (Me 3 SiNPPh 2 ) 2 C) and [Pu(BIPM TMS )(I)(I Me4 ) 2 ] ( 3Pu , I Me4 = C(NMeCMe) 2 ), thus disclosing non-actinyl transneptunium multiple bonds and transneptunium NHC complexes. These Pu-C double and dative bonds, along with cerium, praseodymium, samarium, uranium, and neptunium congeners, enable lanthanide-actinide and actinide-actinide comparisons between metals with similar ionic radii and isoelectronic 4f 5 vs 5f 5 electron-counts within conserved ligand fields over 12 complexes. Quantum chemical calculations reveal that the orbital-energy and spatial-overlap terms increase from uranium to neptunium; however, on moving to plutonium the orbital-energy matching improves but the spatial overlap decreases. The bonding picture that emerges is more complex than the traditional picture of the bonding of lanthanides being ionic and early actinides being more covalent but becoming more ionic left to right. Multiconfigurational calculations on 2M and 3M (M = Pu, Sm) account for the considerably more complex UV/vis/NIR spectra for 5f 5 2Pu and 3Pu compared to 4f 5 2Sm and 3Sm . Supporting the presence of Pu═C double bonds in 2Pu and 3Pu , 2Pu exhibits metallo-Wittig bond metathesis involving the highest atomic number element to date, reacting with benzaldehyde to produce the alkene PhC(H)═C(PPh 2 NSiMe 3 ) 2 ( 4 ) and "PuOI". In contrast, 2Ce and 2Pr do not react with benzaldehyde to produce 4 .

Numerous technologies-with catalytic, therapeutic, and diagnostic applications-would benefit from improved chelation strategies for heavy alkaline earth elements: Ra 2+ , Ba 2+ , and Sr 2+ . Unfortunately, chelating these metals is challenging because of their large size and weak polarizing power. We found 18-crown-6-tetracarboxylic acid ( H 4 COCO ) bound Ra 2+ , Ba 2+ , and Sr 2+ to form M(H x COCO) x -2 . Upon isolating radioactive 223 Ra from its parent radionuclides ( 227 Ac and 227 Th), 223 Ra 2+ reacted with the fully deprotonated COCO 4- chelator to generate Ra(COCO) 2- ( aq ) (log K Ra(COCO)2- = 5.97 ± 0.01), a rare example of a molecular radium complex. Comparative analyses with Sr 2+ and Ba 2+ congeners informed on what attributes engendered success in heavy alkaline earth complexation. Chelators with high negative charge [-4 for Ra(COCO) 2- ( aq ) ] and many donor atoms [≥11 in Ra(COCO) 2- ( aq ) ] provided a framework for stable complex formation. These conditions achieved steric saturation and overcame the weak polarization powers associated with these large dicationic metals.

While uranyl-based metal-organic frameworks (MOFs) boast impressive photocatalytic abilities, significant questions remain regarding their excitation pathways and methods to fine-tune their performance due to the lack of information regarding heterogeneous uranyl catalysis. Herein, we investigated how linker identity and photoexcitation impact uranyl photocatalysis when the uranyl coordination environment remains constant. Toward this end, we prepared three uranyl-based MOFs ( NU-1301 , NU-1307 , and ZnTCPP-U2) and then examined the structural and photochemical properties of each through X-ray diffraction, X-ray absorption, and photoluminescence. We then correlated our observations to the photocatalytic performance for fluorination of cyclooctane. The excitation profile from NU-1301 and NU-1307 exhibited spin-forbidden linker transitions and uranyl vibronic progressions, with uranyl excitation and emission being most dominant in NU-1301 . Consequently, NU-1301 was a more active photocatalyst than NU-1307 . In contrast, the excitation profile from ZnTCPP-U2 contained transitions associated with the porphyrin linker exclusively. Photocatalytic activity from ZnTCPP-U2 significantly underperformed in comparison to that of the other two MOFs. These data suggest that linkers' photophysical properties can be used to predict the photocatalytic behavior of uranyl-containing MOFs.

Modern molten salt reactor design and the techniques of electrorefining spent nuclear fuels require a better understanding of the chemical and physical behavior of lanthanide/actinide ions with different oxidation states dissolved in various solvent salts. The molecular structures and dynamics that are driven by the short-range interactions between solute cations and anions and long-range solute and solvent cations are still unclear. In order to study the structural change of solute cations caused by different solvent salts, we performed first-principles molecular dynamics simulations in molten salts and extended X-ray absorption fine structure (EXAFS) measurements for the cooled molten salt samples to identify the local coordination environment of Eu 2+ and Eu 3+ ions in CaCl 2 , NaCl, and KCl. The simulations reveal that with the increasing polarizing the outer sphere cations from K + to Na + to Ca 2+ , the coordination number (CN) of Cl - in the first solvation shell increases from 5.6 (Eu 2+ ) and 5.9 (Eu 3+ ) in KCl to 6.9 (Eu 2+ ) and 7.0 (Eu 3+ ) in CaCl 2 . This coordination change is validated by the EXAFS measurements, in which the CN of Cl - around Eu increases from 5 in KCl to 7 in CaCl 2 . Our simulation shows that the fewer Cl - ions coordinated to Eu leads to a more rigid first coordination shell with longer lifetime. Furthermore, the diffusivities of Eu 2+ /Eu 3+ are related to the rigidity of their first coordination shell of Cl - : the more rigid the first coordination shell is, the slower the solute cations diffuse.

Plutonium-based technologies would benefit if chemical hazards for purifying plutonium were reduced. One critical processing step where improvements could be impactful is the adjustment of plutonium oxidation-states during separations. This transformation often requires addition of redox agents. Unfortunately, many of the redox agents used previously cannot be used today because their properties are deemed incompatible with modern day processing facilities and waste stream safety requirements. We demonstrated herein that photochemistry can be used as an alternative to those chemical agents. We observed that (1) Pu 4+ → Pu 3+ and UO 2 2+ → U 4+ photoreduction proceeded in HCl (aq) and HNO 3(aq) and (2) photogenerated Pu 3+ (aq) and U 4+ (aq) could be separated using anion exchange chromatography (high yield, >90%; good separation factor, 322).

Historic perspectives describing f-elements as being redox "inactive" are fading. Researchers continue to discover new oxidation states that are not as inaccessible as once assumed for actinides and lanthanides. Inspired by those contributions, we studied americium(III) oxidation in aqueous media under air using NaBiO 3( s ) . We identified selective oxidation of Am 3+ ( aq ) to AmO 2 2+ ( aq ) or AmO 2 1+ ( aq ) could be achieved by changing the aqueous matrix identity. AmO 2 2+ ( aq ) formed in H 3 PO 4( aq ) (1 M) and AmO 2 1+ ( aq ) formed in dilute HCl ( aq ) (0.1 M). These americyl products were stable for weeks in solution. Also included is a method to recover 243 Am from the americium and bismuth mixtures generated during these studies.

Advancing the field of chemical separations is important for nearly every area of science and technology. Some of the most challenging separations are associated with the americium ion Am(III) for its extraction in the nuclear fuel cycle, 241 Am production for industrial usage, and environmental cleanup efforts. Herein, we study a series of extractants, using first-principle calculations, to identify the electronic properties that preferentially influence Am(III) binding in separations. As the most used extractant family and because it affords a high degree of functionalization, the polypyridyl family of extractants is chosen to study the effects of the planarity of the structure, preorganization of coordinating atoms, and substitution of various functional groups. The actinyl ions are used as a structurally simplified surrogate model to quickly screen the most promising candidates that can separate these metal ions. The down-selected extractants are then tested for the Am(III)/Eu(III) system. Our results show that π interactions, especially those between the central terpyridine ring and Am(III), play a crucial role in separation. Adding an electron-donating group onto the terpyridine backbone increases the binding energies to Am(III) and stabilizes Am-terpyridine coordination. Increasing the planarity of the extractant increases the binding strength as well, although this effect is found to be rather weak. Preorganizing the coordinating atoms of an extractant to their binding configuration as in the bound metal complex speeds up the binding process and significantly improves the kinetics of the separation process. This conclusion is validated by the synthesized 1,2-dihydrodipyrido[4,3- b ;5,6- b ]acridine ( 13 ) extractant, a preorganized derivative of the terpyridine extractant, which we experimentally showed was four times more effective than terpyridine at separating Am 3+ from Eu 3+ (SF Am/Eu ∼ 23 ± 1).

Developing chelators that strongly and selectively bind rare-earth elements (Sc, Y, La, and lanthanides) represents a longstanding fundamental challenge in inorganic chemistry. Solving these challenges is becoming more important because of increasing use of rare-earth elements in numerous technologies, ranging from paramagnets to luminescent materials. Within this context, we interrogated the complexation chemistry of the scandium(III) (Sc 3+ ) trication with the hexadentate 1,4,7-triazacyclononane-1,4,7-triacetic acid (H 3 NOTA) chelator. This H 3 NOTA chelator is often regarded as an underperformer for complexing Sc 3+ . A common assumption is that metalation does not fully encapsulate Sc 3+ within the NOTA 3- macrocycle, leaving Sc 3+ on the periphery of the chelate and susceptible to demetalation. Herein, we developed a synthetic approach that contradicted those assumptions. We confirmed that our procedure forced Sc 3+ into the NOTA 3- binding pocket by using single crystal X-ray diffraction to determine the Na[Sc(NOTA)(OOCCH 3 )] structure. Density functional theory (DFT) and 45 Sc nuclear magnetic resonance (NMR) spectroscopy showed Sc 3+ encapsulation was retained when the crystals were dissolved. Solution-phase and DFT studies revealed that [Sc(NOTA)(OOCCH 3 )] 1- could accommodate an additional H 2 O capping ligand. Thermodynamic properties associated with the Sc-OOCCH 3 and Sc-H 2 O capping ligand interactions demonstrated that these capping ligands occupied critical roles in stabilizing the [Sc(NOTA)] chelation complex.

Accurate modeling of the complex electronic structure of actinide complexes requires full inclusion of relativistic effects. In this study, we examine the effect of explicit inclusion of spin-orbit coupling (SOC) versus scalar relativistic effects on the predicted spectra for heavy-element complexes. In this study, we employ a relativistic two-component Hamiltonian in the X2C form with all of the electrons in the system being considered explicitly to compare and contrast with previous studies that included the relativistic effects by means of relativistic effective core potentials (RECPs). A few uranium complexes are chosen as model systems. Comparison of the computed Cl K-edge X-ray absorption spectra with experimental data shows significantly improved agreement when a variational relativistic treatment of SOC is performed. In particular, we note the importance of SOC terms to obtain not only correct transition energies but also correct intensities for these heavy-element complexes because of the redistribution of ligand bonding character among the valence MOs. While RECPs generally agree well with all-electron scalar relativistic calculations, there are some differences in the predicted spectra of open-shell systems. These methods are still suitable for broad application to analyze the qualitative nature of transitions in X-ray absorption spectra, but caution is recommended for quantitative analysis, as SOC can be non-negligible for both open- and closed-shell heavy-element systems.

A cerium-oxo nanocluster capped by chloride ligands, [Ce IV 38- n Ce III n O 56-( n +1) (OH) n +1 Cl 51 (H 2 O) 11 ] 10- ( n = 1-24), has been isolated from acidic chloride solutions by using potassium counterions. The crystal structure was elucidated using single crystal X-ray diffraction. At the center of the cluster is a {Ce 14 } core that exhibits the same fluorite-type structure as bulk CeO 2 , with eight-coordinate Ce sites bridged by tetrahedral oxo anions. The {Ce 14 } is further surrounded by a peripheral shell of six tetranuclear {Ce 4 } subunits that are located on each of the faces of the core to yield the {Ce 38 } cluster. The surface of the cluster is capped by 51 bridging/terminal chloride ligands and 11 water molecules; the anionic cluster is charge balanced by potassium counterions that exist in the outer coordination sphere. While assignment of the Ce oxidation state by bond valence summation was ambiguous, Ce L 3 -edge X-ray absorption, X-ray photoelectron, and UV-vis-NIR absorption results were consistent with a Ce III /Ce IV cluster. Systematic changes in the XANES and UV-vis-NIR absorption spectra over time pointed to reactivity of the cluster upon exposure to air. These changes were examined using single crystal X-ray diffraction, and a clear single-crystal-to-single-crystal transformation was captured; an overall loss of surface-bound chlorides and water molecules as well as new μ 2 -OH sites was observed on the cluster surface. This work provides a rare snapshot of metal oxide cluster reactivity. The results may hold implications for understanding the physical and chemical properties of ceria nanoparticles and provide insight into the behavior of other metal-oxo clusters of significant technological and environmental interest.

Controlling structure and reactivity by manipulating the outer-coordination sphere around a given reagent represents a longstanding challenge in chemistry. Despite advances toward solving this problem, it remains difficult to experimentally interrogate and characterize outer-coordination sphere impact. This work describes an alternative approach that quantifies outer-coordination sphere effects. It shows how molten salt metal chlorides (MCl n ; M = K, Na, n = 1; M = Ca, n = 2) provided excellent platforms for experimentally characterizing the influence of the outer-coordination sphere cations (M n + ) on redox reactions accessible to lanthanide ions; Ln 3+ + e 1- → Ln 2+ (Ln = Eu, Yb, Sm; e 1- = electron). As a representative example, X-ray absorption spectroscopy and cyclic voltammetry results showed that Eu 2+ instantaneously formed when Eu 3+ dissolved in molten chloride salts that had strongly polarizing cations (like Ca 2+ from CaCl 2 ) via the Eu 3+ + Cl 1- → Eu 2+ + ½Cl 2 reaction. Conversely, molten salts with less polarizing outer-sphere M 1+ cations ( e.g. , K 1+ in KCl) stabilized Ln 3+ . For instance, the Eu 3+ /Eu 2+ reduction potential was >0.5 V more positive in CaCl 2 than in KCl. In accordance with first-principle molecular dynamics (FPMD) simulations, we postulated that hard M n + cations (high polarization power) inductively removed electron density from Ln n + across Ln-Cl⋯M n + networks and stabilized electron-rich and low oxidation state Ln 2+ ions. Conversely, less polarizing M n + cations (like K 1+ ) left electron density on Ln n + and stabilized electron-deficient and high-oxidation state Ln 3+ ions.

Diversifying our ability to guard against emerging pathogenic threats is essential for keeping pace with global health challenges, including those presented by drug-resistant bacteria. Some modern diagnostic and therapeutic innovations to address this challenge focus on targeting methods that exploit bacterial nutrient sequestration pathways, such as the desferrioxamine (DFO) siderophore used by Staphylococcus aureus ( S. aureus ) to sequester Fe III . Building on recent studies that have shown DFO to be a versatile vehicle for chemical delivery, we show proof-of-principle that the Fe III sequestration pathway can be used to deliver a potential radiotherapeutic. Our approach replaces the Fe III nutrient sequestered by H 4 DFO + with Th IV and made use of a common fluorophore, FITC, which we covalently bonded to DFO to provide a combinatorial probe for simultaneous chelation paired with imaging and spectroscopy, H 3 DFO&#95;FITC. Combining insight provided from FITC-based imaging with characterization by NMR spectroscopy, we demonstrated that the fluorescent DFO&#95;FITC conjugate retained the Th IV chelation properties of native H 4 DFO + . Fluorescence microscopy with both [Th(DFO&#95;FITC)] and [Fe(DFO&#95;FITC)] complexes showed similar uptake by S. aureus and increased intercellular accumulation as compared to the FITC and unchelated H 3 DFO&#95;FITC controls. Collectively, these results demonstrate the potential for the newly developed H 3 DFO&#95;FITC conjugate to be used as a targeting vector and bacterial imaging probe for S. aureus . The results presented within provide a framework to expand H 4 DFO + and H 3 DFO&#95;FITC to relevant radiotherapeutics (like 227 Th).

Californium (Cf) is currently the heaviest element accessible above microgram quantities. Cf isotopes impose severe experimental challenges due to their scarcity and radiological hazards. Consequently, chemical secrets ranging from the accessibility of 5f/6d valence orbitals to engage in bonding, the role of spin-orbit coupling in electronic structure, and reactivity patterns compared to other f elements, remain locked. Organometallic molecules were foundational in elucidating periodicity and bonding trends across the periodic table 1-3 , with a twenty-first-century renaissance of organometallic thorium (Th) through plutonium (Pu) chemistry 4-12 , and to a smaller extent americium (Am) 13 , transforming chemical understanding. Yet, analogous curium (Cm) to Cf chemistry has lain dormant since the 1970s. Here, we revive air-/moisture-sensitive Cf chemistry through the synthesis and characterization of [Cf(C 5 Me 4 H) 2 Cl 2 K(OEt 2 )] n from two milligrams of 249 Cf. This bent metallocene motif, not previously structurally authenticated beyond uranium (U) 14,15 , contains the first crystallographically characterized Cf-C bond. Analysis suggests the Cf-C bond is largely ionic with a small covalent contribution. Lowered Cf 5f orbital energy versus dysprosium (Dy) 4f in the colourless, isoelectronic and isostructural [Dy(C 5 Me 4 H) 2 Cl 2 K(OEt 2 )] n results in an orange Cf compound, contrasting with the light-green colour typically associated with Cf compounds 16-22 ., (© 2021. This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.)

There is significant interest in ligands that can stabilize actinide ions in oxidation states that can be exploited to chemically differentiate 5f and 4f elements. Applications range from developing large-scale actinide separation strategies for nuclear industry processing to carrying out analytical studies that support environmental monitoring and remediation efforts. Here, we report syntheses and characterization of Np(iv), Pu(iv) and Am(iii) complexes with N-tert -butyl- N -(pyridin-2-yl)hydroxylaminato, [2-( t BuNO)py] - (interchangeable hereafter with [( t BuNO)py] - ), a ligand which was previously found to impart remarkable stability to cerium in the +4 oxidation state. An[( t BuNO)py] 4 (An = Pu, 1 ; Np, 2 ) have been synthesized, characterized by X-ray diffraction, X-ray absorption, 1 H NMR and UV-vis-NIR spectroscopies, and cyclic voltammetry, along with computational modeling and analysis. In the case of Pu, oxidation of Pu(iii) to Pu(iv) was observed upon complexation with the [( t BuNO)py] - ligand. The Pu complex 1 and Np complex 2 were also isolated directly from Pu(iv) and Np(iv) precursors. Electrochemical measurements indicate that a Pu(iii) species can be accessed upon one-electron reduction of 1 with a large negative reduction potential ( E 1/2 = -2.26 V vs. Fc +/0 ). Applying oxidation potentials to 1 and 2 resulted in ligand-centered electron transfer reactions, which is different from the previously reported redox chemistry of U IV [( t BuNO)py] 4 that revealed a stable U(v) product. Treatment of an anhydrous Am(iii) precursor with the [( t BuNO)py] - ligand did not result in oxidation to Am(iv). Instead, the dimeric complex [Am III (μ 2 -( t BuNO)py)(( t BuNO)py) 2 ] 2 ( 3 ) was isolated. Complex 3 is a rare example of a structurally characterized non-aqueous Am-containing molecular complex prepared using inert atmosphere techniques. Predicted redox potentials from density functional theory calculations show a trivalent accessibility trend of U(iii) < Np(iii) < Pu(iii) and that the higher oxidation states of actinides ( i.e. , +5 for Np and Pu and +4 for Am) are not stabilized by [2-( t BuNO)py] - , in good agreement with experimental observations., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

C-term magnetic circular dichroism (MCD) spectroscopy is a powerful method for probing d-d and f-f transitions in paramagnetic metal complexes. However, this technique remains underdeveloped both experimentally and theoretically for studies of U(v) complexes of Oh symmetry, which have been of longstanding interest for probing electronic structure, bonding, and covalency in 5f systems. In this study, C-term NIR MCD of the Laporte forbidden f-f transitions of [UCl6]- and [UF6]- are reported, demonstrating the significant fine structure resolution possible with this technique including for the low energy Γ7 → Γ8 transitions in [UF6]-. The experimental NIR MCD studies were further extended to [U(OC6F5)6]-, [U(CH2SiMe3)6]-, and [U(NC(tBu)(Ph))6]- to evaluate the effects of ligand-type on the f-f MCD fine structure features. Theoretical calculations were conducted to determine the Laporte forbidden f-f transitions and their MCD intensity experimentally observed in the NIR spectra of the U(v) hexahalide complexes, via the inclusion of vibronic coupling, to better understand the underlying spectral fine structure features for these complexes. These spectra and simulations provide an important platform for the application of MCD spectroscopy to this widely studied class of U(v) complexes and identify areas for continued theoretical development.

Covalency is often considered to be an influential factor in driving An 3+ vs. Ln 3+ selectivity invoked by soft donor ligands. This is intensely debated, particularly the extent to which An 3+ /Ln 3+ 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=PPh 2 ) 2 } 3 ] (1-Am, E=Se; 2-Am, E=O) are compared to isoradial [Nd{N(E=PPh 2 ) 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., (© 2021 Wiley-VCH GmbH.)

The positive impact of having access to well-defined starting materials for applied actinide technologies - and for technologies based on other elements - cannot be overstated. Of numerous relevant 5f-element starting materials, those in complexing aqueous media find widespread use. Consider acetic acid/acetate buffered solutions as an example. These solutions provide entry into diverse technologies, from small-scale production of actinide metal to preparing radiolabeled chelates for medical applications. However, like so many aqueous solutions that contain actinides and complexing agents, 5f-element speciation in acetic acid/acetate cocktails is poorly defined. Herein, we address this problem and characterize Ac 3+ and Cm 3+ speciation as a function of increasing acetic acid/acetate concentrations (0.1 to 15 M, pH = 5.5). Results obtained via X-ray absorption and optical spectroscopy show the aquo ion dominated in dilute acetic acid/acetate solutions (0.1 M). Increasing acetic acid/acetate concentrations to 15 M increased complexation and revealed divergent reactivity between early and late actinides. A neutral Ac(H 2 O) 6 (1) (O 2 CMe) 3 (1) compound was the major species in solution for the large Ac 3+ . In contrast, smaller Cm 3+ preferred forming an anion. There were approximately four bound O 2 CMe 1- ligands and one to two inner sphere H 2 O ligands. The conclusion that increasing acetic acid/acetate concentrations increased acetate complexation was corroborated by characterizing (NH 4 ) 2 M(O 2 CMe) 5 (M = Eu 3+ , Am 3+ and Cm 3+ ) using single crystal X-ray diffraction and optical spectroscopy (absorption, emission, excitation, and excited state lifetime measurements)., Competing Interests: The authors have no conflicts of interest with this work., (This journal is © The Royal Society of Chemistry.)

New syntheses have been developed for the synthesis of (borohydrido-κ 3 H )tris-[η 5 -(tri-methyl-sil-yl)cyclo-penta-dien-yl]uranium(IV), [U(BH 4 )(C 8 H 13 Si) 3 ] or Cp' 3 U(BH 4 ) (Cp' = C 5 H 4 SiMe 3 ) and its structure has been determined by single-crystal X-ray crystallography. This compound crystallized in the space group P and the structure features three η 5 -coordinated Cp' rings and a κ 3 -coordinated (BH 4 ) - ligand., (© Windorff et al. 2021.)

Developing targeted α-therapies has the potential to transform how diseases are treated. In these interventions, targeting vectors are labelled with α-emitting radioisotopes that deliver destructive radiation discretely to diseased cells while simultaneously sparing the surrounding healthy tissue. Widespread implementation requires advances in non-invasive imaging technologies that rapidly assay therapeutics. Towards this end, positron emission tomography (PET) imaging has emerged as one of the most informative diagnostic techniques. Unfortunately, many promising α-emitting isotopes such as 225 Ac and 227 Th are incompatible with PET imaging. Here we overcame this obstacle by developing large-scale (Ci-scale) production and purification methods for 134 Ce. Subsequent radiolabelling and in vivo PET imaging experiments in a small animal model demonstrated that 134 Ce (and its 134 La daughter) could be used as a PET imaging candidate for 225 Ac III (with reduced 134 Ce III ) or 227 Th IV (with oxidized 134 Ce IV ). Evaluating these data alongside X-ray absorption spectroscopy results demonstrated how success relied on rigorously controlling the Ce III /Ce IV redox couple.

The transplutonium elements (atomic numbers 95-103) are a group of metals that lie at the edge of the periodic table. As a result, the patterns and trends used to predict and control the physics and chemistry for transition metals, main-group elements and lanthanides are less applicable to transplutonium elements. Furthermore, understanding the properties of these heavy elements has been restricted by their scarcity and radioactivity. This is especially true for einsteinium (Es), the heaviest element on the periodic table that can currently be generated in quantities sufficient to enable classical macroscale studies 1 . Here we characterize a coordination complex of einsteinium, using less than 200 nanograms of 254 Es (with half-life of 275.7(5) days), with an organic hydroxypyridinone-based chelating ligand. X-ray absorption spectroscopic and structural studies are used to determine the energy of the L 3 -edge and a bond distance of einsteinium. Photophysical measurements show antenna sensitization of Es III luminescence; they also reveal a hypsochromic shift on metal complexation, which had not previously been observed in lower-atomic-number actinide elements. These findings are indicative of an intermediate spin-orbit coupling scheme in which j-j coupling (whereby single-electron orbital angular momentum and spin are first coupled to form a total angular momentum, j) prevails over Russell-Saunders coupling. Together with previous actinide complexation studies 2 , our results highlight the need to continue studying the unusual behaviour of the actinide elements, especially those that are scarce and short-lived.

A number of technologies would benefit from developing inorganic compounds and materials with specific electronic and magnetic exchange properties. Unfortunately, designing compounds with these properties is difficult because metal⋅⋅⋅metal coupling schemes are hard to predict and control. Fully characterizing communication between metals in existing compounds that exhibit interesting properties could provide valuable insight and advance those predictive capabilities. One such class of molecules are the series of Lindqvist iron-functionalized and hexavanadium polyoxovanadate-alkoxide clusters, which we characterized here using V K-edge X-ray absorption spectroscopy. Substantial changes in the pre-edge peak intensities were observed that tracked with the V 3d-electron count. The data also suggested substantial delocalization between the vanadium cations. Meanwhile, the Fe III cations were electronically isolated from the polyoxovanadate core., (© 2020 Wiley-VCH GmbH.)

Actinium-225 ( 225 Ac) is an excellent candidate for targeted radiotherapeutic applications for treating cancer, because of its 10-day half-life and emission of four high-energy α 2+ particles. To harness and direct the energetic potential of actinium, strongly binding chelators that remain stable in vivo during biological targeting must be developed. Unfortunately, controlling chelation for actinium remains challenging. Actinium is the largest +3 cation on the periodic table and has a 6d 0 5f 0 electronic configuration, and its chemistry is relatively unexplored. Herein, we present theoretical work focused on improving the understanding of actinium bonding with macrocyclic chelating agents as a function of (1) macrocycle ring size, (2) the number and identity of metal binding functional groups, and (3) the length of the tether linking the metal binding functional group to the macrocyclic backbone. Actinium binding by these chelators is presented within the context of complexation with DOTA 4- , the most relevant Ac 3+ binding agent for contemporary radiopharmaceutical applications. The results enabled us to develop a new strategy for actinium chelator design. The approach is rooted in our identification that Ac 3+ -chelation chemistry is dominated by ionic bonding interactions and relies on (1) maximizing electrostatic interactions between the metal binding functional group and the Ac 3+ cation and (2) minimizing electronic repulsion between negatively charged actinium binding functional groups. This insight will provide a foundation for future innovation in developing the next generation of multifunctional actinium chelators.

We report gamma ray spectroscopy measurements of trinitite samples and analogous samples obtained from detonation sites in Nevada and Semipalatinsk, as well as in situ measurements of topsoil at the Trinity site. We also report the first isotopic composition measurements of trinitite using the novel forensics technique of decay energy spectroscopy (DES) as a complement to traditional forensics techniques. Our gamma spectroscopy and DES measurements are compared to other published results.

With the advent of lanthanide-based technologies, there is a clear need to advance the fundamental understanding of 4f-element chelation chemistry. Herein, we contribute to a growing body of lanthanide chelation chemistry and report the synthesis of bimetallic 4f-element complexes within an imine/hemiacetalate framework, Ln 2 TPT OMe [Ln = lanthanide; TPT OMe = tris(pyridineimine)(Tren)tris(methoxyhemiacetalate); Tren = tris(2-aminoethylamine)]. These products are generated from hydrolysis and methanolysis of the cage ligand tris(pyridinediimine)bis(Tren) ( TPT ; Tadanobu et al. Chem. Lett. 1993 , 22 (5), 859-862) likely facilitated by inductive effects stemming from the Lewis acidic lanthanide cations. These complexes are interesting because they result from imine cleavage to generate two metal binding sites: one pocketed site within the macrocycle and the other terminal site capping a hemiacetalate moiety. A clear demarcation in reactivity is observed between samarium and europium, where the lighter and larger lanthanides generate a mixture of products, Ln 2 TPT OMe and LnTPT . Meanwhile, the heavier and smaller lanthanides generate exclusively bimetallic Ln 2 TPT OMe . The cleavage reactivity to form Ln 2 TPT OMe was extended beyond methanol to include other primary alcohols.

Uranium(IV) complexation by 2-furoic acid (2-FA) was examined to better understand the effects of ligand identity and reaction conditions on species formation and stability. Five compounds were isolated: [UCl 2 (2-FA) 2 (H 2 O) 2 ] n (1), [U 4 Cl 10 O 2 (THF) 6 (2-FA) 2 ]⋅2 THF (2), [U 6 O 4 (OH) 4 (H 2 O) 3 (2-FA) 12 ]⋅7 THF⋅H 2 O (3), [U 6 O 4 (OH) 4 (H 2 O) 2 (2-FA) 12 ]⋅8.76 H 2 O (4), and [U 38 Cl 42 O 54 (OH) 2 (H 2 O) 20 ]⋅m H 2 O⋅n THF (5). The structures were determined by single-crystal X-ray diffraction and further characterized by Raman, IR, and optical absorption spectroscopy. The thermal stability and magnetic behavior of the compounds were also examined. Variations in the synthetic conditions led to notable differences in the structural units observed in the solid state. At low H 2 O/THF ratios, a tetranuclear oxo-bridged [U 4 O 2 ] core was isolated. Aging of this solution resulted in the formation a U 38 oxo cluster capped by chloro and water ligands. However, at increasing water concentrations only hexanuclear units were observed. In all cases, at temperatures of 100-120 °C, UO 2 nanoparticles formed., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Increasing access to the short-lived α-emitting radionuclide astatine-211 ( 211 At) has the potential to advance targeted α-therapeutic treatment of disease and to solve challenges facing the medical community. For example, there are numerous technical needs associated with advancing the use of 211 At in targeted α-therapy, e.g., improving 211 At chelates, developing more effective 211 At targeting, and characterizing in vivo 211 At behavior. There is an insufficient understanding of astatine chemistry to support these efforts. The chemistry of astatine is one of the least developed of all elements on the periodic table, owing to its limited supply and short half-life. Increasing access to 211 At could help address these issues and advance understanding of 211 At chemistry in general. We contribute here an extraction chromatographic processing method that simplifies 211 At production in terms of purification. It utilizes the commercially available Pre-Filter resin to rapidly (<1.5 h) isolate 211 At from irradiated bismuth targets (Bi decontamination factors ≥876 000), in reasonable yield (68-55%) and in a form that is compatible for subsequent in vivo study. We are excited about the potential of this procedure to address 211 At supply and processing/purification problems.

Advances in targeted α-therapies have increased the interest in actinium (Ac), whose chemistry is poorly defined due to scarcity and radiological hazards. Challenges associated with characterizing Ac 3+ chemistry are magnified by its 5f 0 6d 0 electronic configuration, which precludes the use of many spectroscopic methods amenable to small amounts of material and low concentrations (like EPR, UV-vis, fluorescence). In terms of nuclear spectroscopy, many actinium isotopes ( 225 Ac and 227 Ac) are equally "unfriendly" because the actinium α-, β-, and γ-emissions are difficult to resolve from the actinium daughters. To address these issues, we developed a method for isolating an actinium isotope ( 228 Ac) whose nuclear properties are well-suited for γ-spectroscopy. This four-step procedure isolates 228 Ra from naturally occurring 232 Th. The relatively long-lived 228 Ra ( t 1/2 = 5.75(3) years) radioisotope subsequently decays to 228 Ac. Because the 228 Ac decay rate [ t 1/2 = 6.15(2) h] is fast, 228 Ac rapidly regenerates after being harvested from the 228 Ra parent. The resulting 228 Ac generator provides frequent and long-term access (of many years) to the spectroscopically "friendly" 228 Ac radionuclide. We have demonstrated that the 228 Ac product can be routinely "milked" from this generator on a daily basis, in chemically pure form, with high specific activity and in excellent yield (∼95%). Hence, in the same way that developing synthesis routes to new starting materials has advanced coordination chemistry for many metals by broadening access, this 228 Ac generator has the potential to broaden actinium access for the inorganic community, facilitating the characterization of actinium chemical behavior.

X-ray absorption spectroscopy (XAS) beamlines worldwide are steadily increasing their emphasis on full photon-in/photon-out spectroscopies, such as resonant inelastic X-ray scattering (RIXS), resonant X-ray emission spectroscopy (RXES) and high energy resolution fluorescence detection XAS (HERFD-XAS). In such cases, each beamline must match the choice of emission spectrometer to the scientific mission of its users. Previous work has recently reported a miniature tender X-ray spectrometer using a dispersive Rowland refocusing (DRR) geometry that functions with high energy resolution even with a large X-ray spot size on the sample [Holden et al. (2017). Rev. Sci. Instrum. 88, 073904]. This instrument has been used in the laboratory in multiple studies of non-resonant X-ray emission spectroscopy using a conventional X-ray tube, though only for preliminary measurements at a low-intensity microfocus synchrotron beamline. This paper reports an extensive study of the performance of a miniature DRR spectrometer at an unfocused wiggler beamline, where the incident monochromatic flux allows for resonant studies which are impossible in the laboratory. The results support the broader use of the present design and also suggest that the DRR method with an unfocused beam could have important applications for materials with low radiation damage thresholds and that would not survive analysis on focused beamlines.

Previous magnetic, spectroscopic, and theoretical studies of cerocene, Ce(C 8 H 8 ) 2 , have provided evidence for non-negligible 4f-electron density on Ce and implied that charge transfer from the ligands occurs as a result of covalent bonding. Strong correlations of the localized 4f-electrons to the delocalized ligand π-system result in emergence of Kondo-like behavior and other quantum chemical phenomena that are rarely observed in molecular systems. In this study, Ce(C 8 H 8 ) 2 is analyzed experimentally using carbon K-edge and cerium M 5,4 -edge X-ray absorption spectroscopies (XAS), and computationally using configuration interaction (CI) calculations and density functional theory (DFT) as well as time-dependent DFT (TDDFT). Both spectroscopic approaches provide strong evidence for ligand → metal electron transfer as a result of Ce 4f and 5d mixing with the occupied C 2p orbitals of the C 8 H 8 2- ligands. Specifically, the Ce M 5,4 -edge XAS and CI calculations show that the contribution of the 4f 1 , or Ce 3+ , configuration to the ground state of Ce(C 8 H 8 ) 2 is similar to strongly correlated materials such as CeRh 3 and significantly larger than observed for other formally Ce 4+ compounds including CeO 2 and CeCl 6 2- . Pre-edge features in the experimental and TDDFT-simulated C K-edge XAS provide unequivocal evidence for C 2p and Ce 4f covalent orbital mixing in the δ-antibonding orbitals of e 2u symmetry, which are the unoccupied counterparts to the occupied, ligand-based δ-bonding e 2u orbitals. The C K-edge peak intensities, which can be compared directly to the C 2p and Ce 4f orbital mixing coefficients determined by DFT, show that covalency in Ce(C 8 H 8 ) 2 is comparable in magnitude to values reported previously for U(C 8 H 8 ) 2 . An intuitive model is presented to show how similar covalent contributions to the ground state can have different impacts on the overall stability of f-element metallocenes., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A major chemical challenge facing implementation of 225 Ac in targeted alpha therapy-an emerging technology that has potential for treatment of disease-is identifying an 225 Ac chelator that is compatible with in vivo applications. It is unclear how to tailor a chelator for Ac binding because Ac coordination chemistry is poorly defined. Most Ac chemistry is inferred from radiochemical experiments carried out on microscopic scales. Of the few Ac compounds that have been characterized spectroscopically, success has only been reported for simple inorganic ligands. Toward advancing understanding in Ac chelation chemistry, we have developed a method for characterizing Ac complexes that contain highly complex chelating agents using small quantities (μg) of 227 Ac. We successfully characterized the chelation of Ac 3+ by DOTP 8- using EXAFS, NMR, and DFT techniques. To develop confidence and credibility in the Ac results, comparisons with +3 cations (Am, Cm, and La) that could be handled on the mg scale were carried out. We discovered that all M 3+ cations (M = Ac, Am, Cm, La) were completely encapsulated within the binding pocket of the DOTP 8- macrocycle. The computational results highlighted the stability of the M(DOTP) 5- complexes.

We report the small-scale synthesis, isolated yield, single-crystal X-ray structure, 1 H NMR solution spectroscopy /solid-state UV/Vis-nIR spectroscopy, and density functional theory (DFT)/ab initio wave function theory calculations on an Am 3+ organometallic complex, [Am(C 5 Me 4 H) 3 ] (1). This constitutes the first quantitative data on Am-C bonding in a molecular species., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Radionuclides find widespread use in medical technologies for treating and diagnosing disease. Among successful and emerging radiotherapeutics, 119 Sb has unique potential in targeted therapeutic applications for low-energy electron-emitting isotopes. Unfortunately, developing 119 Sb-based drugs has been slow in comparison to other radionuclides, primarily due to limited accessibility. Herein is a production method that overcomes this challenge and expands the available time for large-scale distribution and use. Our approach exploits high flux and fluence from high-energy proton sources to produce longer lived 119m Te. This parent isotope slowly decays to 119 Sb, which in turn provides access to 119 Sb for longer time periods (in comparison to direct 119 Sb production routes). We contribute the target design, irradiation conditions, and a rapid procedure for isolating the 119m Te/ 119 Sb pair. To guide process development and to understand why the procedure was successful, we characterized the Te/Sb separation using Te and Sb K-edge X-ray absorption spectroscopy. The procedure provides low-volume aqueous solutions that have high 119m Te-and consequently 119 Sb-specific activity in a chemically pure form. This procedure has been demonstrated at large-scale (production-sized, Ci quantities), and the product has potential to meet stringent Food and Drug Administration requirements for a 119m Te/ 119 Sb active pharmaceutical ingredient., Competing Interests: The authors declare no competing financial interest.

X-ray absorption fine structure (XAFS) and x-ray emission spectroscopy (XES) are advanced x-ray spectroscopies that impact a wide range of disciplines. However, unlike the majority of other spectroscopic methods, XAFS and XES are accompanied by an unusual access model, wherein the dominant use of the technique is for premier research studies at world-class facilities, i.e., synchrotron x-ray light sources. In this paper, we report the design and performance of an improved XAFS and XES spectrometer based on the general conceptual design of Seidler et al. [Rev. Sci. Instrum. 85, 113906 (2014)]. New developments include reduced mechanical degrees of freedom, much-increased flux, and a wider Bragg angle range to enable extended x-ray absorption fine structure (EXAFS) measurement and analysis for the first time with this type of modern laboratory XAFS configuration. This instrument enables a new class of routine applications that are incompatible with the mission and access model of the synchrotron light sources. To illustrate this, we provide numerous examples of x-ray absorption near edge structure (XANES), EXAFS, and XES results for a variety of problems and energy ranges. Highlights include XAFS and XES measurements of battery electrode materials, EXAFS of Ni with full modeling of results to validate monochromator performance, valence-to-core XES for 3d transition metal compounds, and uranium XANES and XES for different oxidation states. Taken en masse, these results further support the growing perspective that modern laboratory-based XAFS and XES have the potential to develop a new branch of analytical chemistry.

Linkage isomers of reduced metal-nitrosyl complexes serve as key species in nitric oxide (NO) reduction at monometallic sites to produce nitrous oxide (N 2 O), a potent greenhouse gas. While factors leading to extremely rare side-on nitrosyls are unclear, we describe a pair of nickel-nitrosyl linkage isomers through controlled tuning of noncovalent interactions between the nitrosyl ligands and differently encapsulated potassium cations. Furthermore, these reduced metal-nitrosyl species with N-centered spin density undergo radical coupling with free NO and provide a N-N coupled cis-hyponitrite intermediate whose protonation triggers the release of N 2 O. This report outlines a stepwise molecular mechanism of NO reduction to form N 2 O at a mononuclear metal site that provides insight into the related biological reduction of NO to N 2 O.

We demonstrate that vacuum forming of 10-cm diameter silicon wafers of various crystallographic orientations under an x-ray permeable, flexible window can easily generate spherically bent crystal analyzers and toroidally bent crystal analyzers with ∼1-eV energy resolution and a 1-m major radius of curvature. In applications at synchrotron light sources, x-ray free electron lasers, and laboratory spectrometers, these characteristics are generally sufficient for many x-ray absorption fine structure (XAFS), x-ray emission spectroscopy (XES), and resonant inelastic x-ray scattering applications in the chemical sciences. Unlike existing optics manufacturing methods using epoxy or anodic bonding, vacuum forming without adhesive is temporary in the sense that the bent wafer can be removed when vacuum is released and exchanged for a different orientation wafer. Therefore, the combination of an x-ray compatible vacuum-forming chamber, a library of thin wafers, and a small number of forms having different secondary curvatures can give extreme flexibility in spectrometer energy range. As proof of this method, we determine the energy resolution and reflectivity for several such vacuum-formed bent crystal analyzers in laboratory-based XAFS and XES studies using a conventional x-ray tube. For completeness, we also show x-ray images collected on the detector plane to characterize the resulting focal spots and optical aberrations.

Evaluating the nature of chemical bonding for actinide elements represents one of the most important and long-standing problems in actinide science. We directly address this challenge and contribute a Cl K-edge X-ray absorption spectroscopy and relativistic density functional theory study that quantitatively evaluates An-Cl covalency in AnCl 6 2- (An IV = Th, U, Np, Pu). The results showed significant mixing between Cl 3p- and An IV 5f- and 6d-orbitals (t 1u */t 2u * and t 2 g */e g *), with the 6d-orbitals showing more pronounced covalent bonding than the 5f-orbitals. Moving from Th to U, Np, and Pu markedly changed the amount of M-Cl orbital mixing, such that An IV 6d - and Cl 3p-mixing decreased and metal 5f - and Cl 3p-orbital mixing increased across this series.

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.

Understanding actinide(iii) (An III = Cm III , Am III , Ac III ) solution-phase speciation is critical for controlling many actinide processing schemes, ranging from medical applications to reprocessing of spent nuclear fuel. Unfortunately, in comparison to most elements in the periodic table, An III speciation is often poorly defined in complexing aqueous solutions and in organic media. This neglect - in large part - is a direct result of the radioactive properties of these elements, which make them difficult to handle and acquire. Herein, we surmounted some of the handling challenges associated with these exotic 5f-elements and characterized Cm III , Am III , and Ac III using An III L 3 -edge X-ray absorption spectroscopy (XAS) as a function of increasing nitric acid (HNO 3 ) concentration. Our results revealed that actinide aquo ions, An(H 2 O) x 3+ ( x = 9.6 ± 0.7, 8.9 ± 0.8, and 10.0 ± 0.9 for Cm III , Am III , and Ac III ), were the dominant species in dilute HNO 3 (0.05 M). In concentrated HNO 3 (16 M), shell-by-shell fitting of the extended X-ray fine structure (EXAFS) data showed the nitrate complexation increased, such that the average stoichiometries of Cm(NO 3 ) 4.1±0.7 (H 2 O) 5.7±1.3 (1.1±0.2)- , Am(NO 3 ) 3.4±0.7 (H 2 O) 5.4±0.5 (0.4±0.1)- , and Ac(NO 3 ) 2.3±1.7 (H 2 O) 8.3±5.2 (0.7±0.5)+ were observed. Data obtained at the intermediate HNO 3 concentration (4 M) were modeled as a linear combination of the 0.05 and 16 M spectra. For all three metals, the intermediate models showed larger contributions from the 0.05 M HNO 3 spectra than from the 16 M HNO 3 spectra. Additionally, these efforts enabled the Cm-NO 3 and Ac-NO 3 distances to be measured for the first time. Moreover, the An III L 3 -edge EXAFS results, contribute to the growing body of knowledge associated with Cm III , Am III , and Ac III coordination chemistry, in particular toward advancing understanding of An III solution phase speciation.

A series of uranium amides were synthesized from N, N, N-cyclohexyl(trimethylsilyl)lithium amide [Li][N(TMS)Cy] and uranium tetrachloride to give U(NCySiMe 3 ) x (Cl) 4- x , where x = 2, 3, or 4. The diamide was isolated as a bimetallic, bridging lithium chloride adduct ((UCl 2 (NCyTMS) 2 ) 2 -LiCl(THF) 2 ), and the tris(amide) was isolated as the lithium chloride adduct of the monometallic species (UCl(NCyTMS) 3 -LiCl(THF) 2 ). The tetraamide complex was isolated as the four-coordinate pseudotetrahedron. Cyclic voltammetry revealed an easily accessible reversible oxidation wave, and upon chemical oxidation, the U V amido cation was isolated in near-quantitative yields. The synthesis of this family of compounds allows a direct comparison of the electronic structure and properties of isostructural U IV and U V tetraamide complexes. Spectroscopic investigations consisting of UV-vis, NIR, MCD, EPR, and U L 3 -edge XANES, along with density functional and wave function calculations, of the four-coordinate U IV and U V complexes have been used to understand the electronic structure of these pseudotetrahedral complexes.