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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

A tetrahedral neptunium(V) complex

Neptunium is an actinide element sourced from anthropogenic production, and, unlike naturally abundant uranium, its coordination chemistry is not well developed in all accessible oxidation states. High-valent neptunium generally requires stabilization from at least one metal–ligand multiple bond, and departing from this structural motif poses a considerable challenge. Here we report a tetrahedral molecular neptunium(V) complex ([Np 5+ (NPC) 4 ][B(ArF 5 ) 4 ], 1-Np) (NPC = [NP t Bu(pyrr) 2 ] − ; t Bu = C(CH 3 ) 3 ; pyrr = pyrrolidinyl (N(C 2 H 4 ) 2 ); B(ArF 5 ) 4 = tetrakis(2,3,4,5,6-pentafluourophenyl)borate). Single-crystal X-ray diffraction, solution-state spectroscopy and density functional theory studies of 1-Np and the product of its proton-coupled electron transfer (PCET) reaction, 2-Np, demonstrate the unique bonding that stabilizes this reactive ion and establishes the thermochemical and kinetic parameters of PCET in a condensed-phase transuranic complex. The isolation of this four-coordinate, neptunium(V) complex reveals a fundamental reaction pathway in transuranic chemistry.

coordination chemistry↗
DOE OSTI2025

Praseodymium in the formal +5 oxidation state

Praseodymium in the +5 oxidation state is a long-sought connection between lanthanide, early-transition and actinide metal redox chemistries. Unique among the lanthanide series, evidence for molecular pentavalent praseodymium species has been observed in the gas phase and noble gas matrix isolation conditions. Here we report the low-temperature synthesis and characterization of a molecular praseodymium complex in the formal +5 oxidation state, [Pr 5+ (NP t Bu 3 ) 4 ][X − ] (where t Bu = tert -butyl and X − = tetrakis(pentafluorophenyl)borate or hexafluorophosphate). Single-crystal X-ray diffraction, solution-state spectroscopic, solution magnetometric, density functional theory and multireference wavefunction-based methods indicate a highly multiconfigurational singlet ground state. Finally, an inverted ligand field drives this unique electronic structure, which establishes a critical link in understanding the bonding of high-valent metal complexes across the periodic table.

chemical bonding↗
DOE OSTI2020

Actinide 2-metallabiphenylenes that satisfy Hückel’s rule

Aromaticity and antiaromaticity, as defined by Hückel’s rule, are key ideas in organic chemistry, and are both exemplified in biphenylene—a molecule that consists of two benzene rings joined by a four-membered ring at its core. Biphenylene analogues in which one of the benzene rings has been replaced by a different (4n + 2) π-electron system have so far been associated only with organic compounds. In addition, efforts to prepare a zirconabiphenylene compound resulted in the isolation of a bis(alkyne) zirconocene complex instead. Here we report the synthesis and characterization of, to our knowledge, the first 2-metallabiphenylene compounds. Single-crystal X-ray diffraction studies reveal that these complexes have nearly planar, 11-membered metallatricycles with metrical parameters that compare well with those reported for biphenylene. Nuclear magnetic resonance spectroscopy, in addition to nucleus-independent chemical shift calculations, provides evidence that these complexes contain an antiaromatic cyclobutadiene ring and an aromatic benzene ring. Finally, spectroscopic evidence, Kohn–Sham molecular orbital compositions and natural bond orbital calculations suggest covalency and delocalization of the uranium f 2 electrons with the carbon-containing ligand.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Materials synthesis at terapascal static pressures

Theoretical modelling predicts very unusual structures and properties of materials at extreme pressure and temperature conditions. Hitherto, their synthesis and investigation above 200 gigapascals have been hindered both by the technical complexity of ultrahigh-pressure experiments and by the absence of relevant in situ methods of materials analysis. Here we report on a methodology developed to enable experiments at static compression in the terapascal regime with laser heating. We apply this method to realize pressures of about 600 and 900 gigapascals in a laser-heated double-stage diamond anvil cell, producing a rhenium–nitrogen alloy and achieving the synthesis of rhenium nitride Re 7 N 3 —which, as our theoretical analysis shows, is only stable under extreme compression. Full chemical and structural characterization of the materials, realized using synchrotron single-crystal X-ray diffraction on microcrystals in situ, demonstrates the capabilities of the methodology to extend high-pressure crystallography to the terapascal regime.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Design of metal-mediated protein assemblies via hydroxamic acid functionalities

The self-assembly of proteins into sophisticated multicomponent assemblies is a hallmark of all living systems and has spawned extensive efforts in the construction of novel synthetic protein architectures with emergent functional properties. Protein assemblies in nature are formed via selective association of multiple protein surfaces through intricate noncovalent protein-protein interactions, a challenging task to accurately replicate in the de novo design of multiprotein systems. In this protocol, we describe the application of metal-coordinating hydroxamate (HA) motifs to direct the metal-mediated assembly of polyhedral protein architectures and 3D crystalline protein frameworks (protein-MOFs). This strategy has been implemented using an asymmetric cytochrome cb562 monomer through selective, concurrent association of Fe 3+ and Zn 2+ ions to form polyhedral cages. Furthermore, the use of ditopic HA linkers as bridging ligands with metal-binding protein nodes has allowed the construction of crystalline 3D protein-MOF lattices. The protocol is divided into two major sections: (1) the development of a Cys-reactive HA molecule for protein derivatization and self-assembly of protein-HA conjugates into polyhedral cages and (2) the synthesis of ditopic HA bridging ligands for the construction of ferritin-based protein-MOFs using symmetric metal-binding protein nodes. Furthermore, protein cages can be analyzed using analytical ultracentrifugation (AUC), transmission electron microscopy (TEM) and single-crystal X-ray diffraction (sc-XRD) techniques. HA-mediated protein-MOFs are formed in sitting-drop vapor diffusion crystallization trays and are probed via sc-XRD and multi-crystal small-angle X-ray scattering (SAXS) measurements. Ligand synthesis, construction of HA-mediated assemblies, and post-assembly analysis as described in this protocol can be performed by a graduate-level researcher within six weeks.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Water-carbon dioxide solid phase equilibria at pressures above 4 GPa

A solid phase in the mixed water-carbon dioxide system, previously identified as carbonic acid, was observed in the high-pressure diamond-anvil cell. The pressure-temperature paths of both its melting and peritectic curves were measured, beginning at 4.4GPa and 165°C (where it exists in a quadruple equilibrium, together with an aqueous fluid and the ices H2O(VII) and CO2(I)) and proceeding to higher pressures and temperatures. Single-crystal X-ray diffraction revealed a triclinic crystal with unit cell parameters (at 6.5GPa and 20°C) of a=5.88Å, b=6.59Å, c=6.99Å, α=88.7°, β=79.7°, and γ=67.7°. Raman spectra exhibit a major line at ~1080cm-1 and lattice modes below 300cm-1.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Mn-induced Ferromagnetic Semiconducting Behavior with Linear Negative Magnetoresistance in Sr 4 (Ru 1-x Mn x ) 3 O 10 Single Crystals

Triple-layered Sr 4 Ru 3 O 10 is a unique ferromagnet with the central RuO 6 layer behaving differently from two outer layers both crystallographically and magnetically. Here, we report that the partial substitution of Ru by smaller Mn gives rise to modification in crystal structure, electronic and magnetic properties of Sr 4 (Ru 1-x Mn x ) 3 O 10 . Through the single crystal X-ray diffraction refinement, we find that (Ru/Mn)O 6 octahedral rotation is no longer detectable at x ≥ 0.23, leading to the tetragonal structure. The magnetization measurements indicate the ferromagnetic transition temperature T C decreases from 105 K for x = 0 to 30 K for x = 0.41, with the reduced magnetic moment as well. Remarkably, Mn doping results in the change of magnetic anisotropy from the easy c axis in x = 0 to the easy ab plane seen in x = 0.34 and 0.41. Such change also removes the ab -plane metamagnetic transition observed in x = 0. Furthermore, the electrical resistivity increases with increasing x showing semiconducting behavior with Δ ~ 10 meV for x = 0.34 and 30 meV for x = 0.41. Under applied magnetic field, the magnetoresistance exhibits negative and linear field dependence in all current and field configurations. These results clearly indicate Sr 4 (Ru 1-x Mn x ) 3 O 10 is a novel ferromagnetic semiconductor with exotic magnetotransport properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Single crystal structure, vibrational spectroscopy, gas sorption and antimicrobial properties of a new inorganic acidic diphosphates material (NH 4 ) 2 Mg(H 2 P 2 O 7 ) 2 • 2 H 2 O

We report on the successful synthesis of diammonium magnesium dihydrogendiphosphate (V) dihydrate compound (NH 4 ) 2 Mg(H 2 P 2 O 7 ) 2 •2H 2 O using a wet chemical route. Single crystal X-ray diffraction analysis and micro Raman spectroscopy are employed to characterize the compound. We demonstrate, using a multidisciplinary approach, that this compound is ideal for carbon dioxide (CO 2 ) capture in addition to other anthropogenic gasses. We show here -from both an experimental as well as from a density functional theory (DFT) calculations routes- the potential for adopting this compound into domestic air-conditioning units (ACUs). From these experiments, the resistance to bacterial growth is also investigated, which is critical for the adoption of this compound in ACUs. Our compound exhibits a higher methane (CH 4 ) sorptivity as compared to CO 2 at 25 °C and 45 °C under pressures up to 50 bars. Furthermore, DFT electronic structure calculations are used to compute the main structural and electronic properties of the compound, taking into consideration the characteristics of the identified pores as a function of the progressive CO 2 vs. CH 4 loadings. Finally, the antibacterial assay reveals a strong antibacterial activity against the tested Gram-positive and Gram-negative bacteria, with a large zone of inhibition against the tested E. Coli, S. Aureus and K. Pneumonia

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Developing scandium and yttrium coordination chemistry to advance theranostic radiopharmaceuticals

The octadentate siderophore analog 3,4,3-LI(1,2-HOPO), denoted 343-HOPO hereafter, is known to have high affinity for both trivalent and tetravalent lanthanide and actinide cations. Here we extend its coordination chemistry to the rare-earth cations Sc$^{3+}$ and Y$^{3+}$ and characterize fundamental metal–chelator binding interactions in solution via UV-Vis spectrophotometry, nuclear magnetic resonance spectroscopy, and spectrofluorimetric metal-competition titrations, as well as in the solid-state via single crystal X-ray diffraction. Sc$^{3+}$ and Y$^{3+}$ binding with 343-HOPO is found to be robust, with both high thermodynamic stability and fast room temperature radiolabeling, indicating that 343-HOPO is likely a promising chelator for in vivo applications with both metals. As a proof of concept, we prepared a $^{86}$Y-343-HOPO complex for in vivo PET imaging, and the results presented herein highlight the potential of 343-HOPO chelated trivalent metal cations for therapeutic and theranostic applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Bonding and reactivity of isostructural uranyl and neptunyl peroxide phases

Understanding the reactivity of actinide peroxides is critical for predicting the behavior of spent nuclear fuel in radiolytic environments. Herein, we report the synthesis and characterization of a lithium neptunyl(VI) hydroxo peroxo compound (LiNp), which is isostructural to the uranyl analogue (LiU). Single-crystal X-ray diffraction reveals that LiNp contains both [NpO 2 (O 2 ) 3 ] 4- and [NpO 2 (OH) 4 ] 2- units stabilized by Li + and hydrogen bonding and Raman spectroscopy shows systematic redshifts in neptunyl vibrational modes relative to uranyl. DFT calculations highlight the importance of secondary coordination in reproducing vibrational and structural features, but challenges remain with correctly modeling strong sigma donors. Solid-state EPR spectroscopy and DFT confirm superoxide stabilization within LiU and calculations suggest favorability of the analogous radical species in LiNp. Solution state EPR spectroscopy with the radical spin trap 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BMPO) reveal evidence of superoxide in the LiU and LiNp phases and suggests stabilization of superoxide within actinyl triperoxide complexes, forming [AnO 2 (O 2 ) 2 (O) 2 • ] 3- .

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Discovery of charge order above room-temperature in the prototypical kagome superconductor La(Ru1−xFex)3Si2

Abstract The kagome lattice is an intriguing and rich platform for discovering, tuning and understanding the diverse phases of quantum matter, crucial for advancing modern and future electronics. Despite considerable efforts, accessing correlated phases at room temperature has been challenging. Using single-crystal X-ray diffraction, we discovered charge order above room temperature in La(Ru 1−x Fe x ) 3 Si 2 (x= 0, 0.01, 0.05), where charge order related to out-of-plane Ru atom displacements appears belowT CO,I ≃ 400 K. The secondary charge ordered phase emerges belowT CO,II ≃ 80–170 K. Furthermore, first principles calculations reveal both the kagome flat band and the van Hove point near the Fermi energy in LaRu 3 Si 2 , driven by Ru-dz 2 orbitals. Our results identify LaRu 3 Si 2 as the kagome superconductor with the highest known charge ordering temperature, offering a promising avenue for researching room temperature quantum phases and developing related technologies.

Physics↗
DOE OSTI2016

Gd 3 Ni 2 and Gd 3 Co x Ni 2-x : magnetism and unexpected Co/Ni crystallographic ordering

The crystal structure, composition and physical properties of Gd 3 Ni 2 , which was earlier reported to exist in the Gd–Ni system without any details of its structure and properties, have been determined. This rare earth binary compound is a high-temperature phase: it forms via a peritectic reaction at 988 K (715 °C) and decomposes below ≈923 K (650 °C). The compound can be retained at room temperature as a metastable phase by quenching after high temperature annealing. Gd 3 Ni 2 crystallizes in the monoclinic Dy 3 Ni 2 structure type [mS20, C2/m (No. 12), Z = 4; with lattice parameters a = 13.418(3) Å, b = 3.720(1) Å, c = 9.640(2) Å, β = 106.250(3)°]. Ni can be substituted by Co up to 50% (i.e. up to and including Gd 3 CoNi) with no change in the structural prototype; the substitution of Co for Ni stabilizes the R 3 Co x Ni 2-x phases down to room temperature. The crystal structure, magnetic properties and magnetocaloric effect (MCE) have been investigated for both Gd 3 Ni 2 and the related Gd 3 Co x Ni 2-x solid solution alloys (0 ≤ x ≤ 1). The crystal structure of the Gd 3 CoNi is a ternary ordered derivative of the monoclinic Dy 3 Ni 2 -type, where Co fully occupies only one of the two 4i Wyckoff sites available for the transition metal. To the best of our knowledge, this is the first example of an intermetallic phase showing ordered site occupations by the chemically quite similar elements Co and Ni. All compounds show long range ferromagnetic ordering, with T C progressively increasing from 147 K (for Gd 3 Ni 2 ) to 176 K (for Gd 3 CoNi) as a cubic function of the Co content. Evidence of Co contributing to the magnetic interactions in these compounds has been found. First-principles total energy calculations predicted the ordered occupation of Co and Ni at the crystallographic sites of Gd3CoNi, which was later confirmed by single crystal X-ray diffraction. The increased conduction electronic state (3d) exchange splitting at the Fermi level supports the experimentally observed enhanced Curie temperature in Gd 3 CoNi compared to Gd 3 Ni 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Controlling superstructural ordering in the clathrate-I Ba 8 M 16 P 30 (M = Cu, Zn) through the formation of metal–metal bonds

Order–disorder–order phase transitions in the clathrate-I Ba 8 Cu 16 P 30 were induced and controlled by aliovalent substitutions of Zn into the framework. Unaltered Ba 8 Cu 16 P 30 crystallizes in an ordered orthorhombic ( Pbcn ) clathrate-I superstructure that maintains complete segregation of metal and phosphorus atoms over 23 different crystallographic positions in the clathrate framework. The driving force for the formation of this Pbcn superstructure is the avoidance of Cu–Cu bonds. This superstructure is preserved upon aliovalent substitution of Zn for Cu in Ba 8 Cu 16– x Zn x P 30 with 0 < x < 1.6 (10% Zn/M total ), but vanishes at greater substitution concentrations. Higher Zn concentrations (up to 35% Zn/M total ) resulted in the additional substitution of Zn for P in Ba 8 M 16+ y P 30– y (M = Cu, Zn) with 0 ≤ y ≤ 1. This causes the formation of Cu–Zn bonds in the framework, leading to a collapse of the orthorhombic superstructure into the more common cubic subcell of clathrate-I ( Pm n ). In the resulting cubic phases, each clathrate framework position is jointly occupied by three different elements: Cu, Zn, and P. Detailed structural characterization of the Ba–Cu–Zn–P clathrates-I via single crystal X-ray diffraction, joint synchrotron X-ray and neutron powder diffractions, pair distribution function analysis, electron diffraction and high-resolution electron microscopy, along with elemental analysis, indicates that local ordering is present in the cubic clathrate framework, suggesting the evolution of Cu–Zn bonds. For the compounds with the highest Zn content, a disorder–order transformation is detected due to the formation of another superstructure with trigonal symmetry and Cu–Zn bonds in the clathrate-I framework. It is shown that small changes in the composition, synthesis, and crystal structure have significant impacts on the structural and transport properties of Zn-substituted Ba 8 Cu 16 P 30 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Schiff-base coordination complexes with plutonium( iv ) and cerium( iv )

PuL 2 and CeL 2 (L = N,N'-bis[(4,4'-diethylamino)salicylidene]-1,2-phenylenediamine) have been synthesized, and characterized by single crystal X-ray diffraction, UV/vis/NIR spectroscopy, and cyclic voltammetry. Furthermore, these studies reveal the enhanced stabilization of Pu(IV) versus Ce(IV) with this Schiff base, and quasi-reversible redox behavior only with the plutonium complex.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Streams, cascades, and pools: various water cluster motifs in structurally similar Ni(ii) complexes

Hydrogen bonding (HB) interactions are well known to impact the properties of water in the bulk and within hydrated materials. A series of Ni(II) complexes based on chelates containing N-(2-aminoethyl)-1-methylimidazole-2-carboxamide have been synthesized and fully characterized by single crystal X-ray diffraction, spectroscopic methods, and thermal analysis. The complexes reveal a variety of water cluster motifs dependent on the packing arrangement in the solid state. A key feature is the orientation of the carboxamide moiety, which leads to the formation of void spaces that accommodate water through HB interactions. The water motifs contain 1D water chains (streams), 2D tapes of infused rings (cascades), and isolated water dimers (pools). The HB motifs in the hydrated structures vary as a function of the crystal packing of the host molecules. Thermal analyses show a correlation between the HB motif in the hydrated crystals and the temperature range of the dehydration process. The conductivity of the hydrated crystals varies as a function of the crystal packing interactions between metal complexes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

A series of dithiocarbamates for americium, curium, and californium

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 in this paper help to address this issue through isolation of An(S 2 CNEt 2 ) 3 (N 2 C 12 H 8 ) (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(S 2 CNEt 2 ) 3 (N 2 C 12 H 8 ) for providing a test bed for comparative analyses of actinide versus lanthanide bonding interactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Exploring crown-ether functionalization on the stabilization of hexavalent neptunium

Crown-ether molecules are used in radiochemical separations due to their high selectivity for a range of metal cations. Previous investigations regarding the interactions of 18-crown-6 (18C6) with 237 Np suggested the formation of a Np(V) inclusion complex, but also reported rapid reduction of Np(VI) to Np(V) in the presence of the ether molecule. Herein, we investigate the impact of crown ether functionalization by exploring the Np(V) and Np(VI) dicyclohexano-18-crown-6 (DCH-18C6) systems. Two [X(DCH-18C6)] 2 [Np(VI)O 2 Cl 4 ] compounds (X = K (1) and Na (2)) were crystallized and characterized by single crystal X-ray diffraction and Raman spectroscopy. Additional studies of Np(VI), Np(V), and Np(V)/Np(VI) in solution indicated redox stability in the presence of functionalized crowns and preferential crystallization of Np(VI) DCH-18C6 solids. Furthermore, these results indicate that functionalization of the crown can lead to higher resistance to radiolysis and increased stability of the Np(VI) oxidation state in solution.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Single crystal structure and photocatalytic behavior of grafted uranyl on the Zr-node of a pyrene-based metal–organic framework

Accurately characterizing actinide oxides bound to metal–organic frameworks (MOFs) is important for designing MOFs as radioactive waste sorbents and catalytic supports. Here, the zirconium MOF NU-1000 was post-synthetically modified through solvothermal deposition to include the uranyl (UO 2 2+ ) ion and characterized via single-crystal X-ray diffraction. Additonally, bond lengths derived from the diffraction pattern and Raman spectroscopy indicate that UO 2 2+ maintains its chemical properties upon deposition, while alcohol oxidation photocatalysis reveals photo-interactions between the pyrene linkers and the UO 2 2+ ion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗