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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Production and radiochemistry of the in vivo PET generator 140 Nd/ 140 Pr as an imaging surrogate for F-block therapeutic radionuclides

Theranostics, a combined approach of diagnostics and therapeutics, often employs F-block therapeutic radionuclides including 225 Ac, 177 Lu, and 161 Tb. While there is a lack of F-block PET imaging radionuclides, the in vivo PET generator pair 140 Nd/ 140 Pr can act as a theranostic imaging counterpart to the F-block therapeutic radionuclides. In this study, we explored the production and separation of high purity 140 Nd via the 141 Pr(p,2n) 140 Nd reaction route. Monoisotopic 141 Pr targets irradiated with 20 MeV protons for 10 min with 10 µA beam current yielded 21.45 ± 0.82 MBq (580 ± 22 µCi) of 140 Nd. A two-step separation method was developed for the purification of 140 Nd from the 141 Pr target material. Recoveries of 27.4 ± 2.1% 140Nd were obtained upon separation with < 20 ppb of 141 Pr target material in the final product. Radiolabeling of Macropa and DOTA chelators with 140 Nd resulted in [ 140 Nd]Nd-Macropa with a molar activity of 74.0 MBq/µmol (2.0 mCi/µmol) and [ 140 Nd]Nd-DOTA with a molar activity of 70.3 MBq/µmol (1.9 mCi/µmol). An imaging study with a phantom indicated the PET spatial resolution of 140 Nd/ 140 Pr was distinguishable down to 2.4 mm. This study sets the stage for the 140 Nd/ 140 Pr in vivo PET generator to be explored in radiopharmaceutical applications.

F-block↗
DOE OSTI2026

Production and performance of a 172 Hf/ 172 Lu generator

A 172 Hf/ 172 Lu radionuclide generator system to produce 172 Lu for laboratory scale applications in lutetium-based radiochemistry development was established and evaluated. The parent 172 Hf radionuclide was produced through 35.2 MeV proton irradiation of natural lutetium metal foil at the Brookhaven Linac Isotope Producer. Four resins were investigated for 172 Hf separation from bulk Lu target material: LN resin, ZR resin, in-house synthesized hydroxamate, and methyl-substituted hydroxamate resins, all with comparable performance. Separated 172 Hf was consolidated and used to create a ZR resin-based 4.9(3) MBq 172 Hf/ 172 Lu generator which was eluted 49 times over two years with no observed breakthrough of 172 Hf, and an average elution efficiency of 98(1)%. The eluted 172 Lu was used to radiolabel the macrocyclic chelator DOTA with an apparent molar activity of 8(2)x10 2 kBq/nmol.

172Hf/172Lu radionuclide generator↗
DOE OSTI2025

18-membered macrocycle appended on resin for selective rare earth element extraction and separation

The rare earth elements are critically important for a wide range of modern technologies. However, obtaining them selectively and efficiently from natural sources and recycled materials is challenging and often requires harsh or wasteful conditions. Here we show that a macrocyclic chelator appended to a solid resin can overcome this challenge by acting as a robust platform for both the extraction and separation of these elements. This resin preferably captures the large rare earth elements in mixtures of these ions, giving rise to higher extraction efficiencies for them over the smaller ions. We further demonstrate that this resin can be used to separate rare earth elements. As a proof-of-principle validation, this resin was demonstrated to selectively extract rare earth elements in the presence of many different types of competing metal ions in a bioleachate solution obtained from autoslag waste, leading to their enrichment.

Coordination chemistry↗
DOE OSTI2020

Nickel(ii)-methyl complexes adopting unusual seesaw geometries

Here, we report four-coordinate nickel(II)-methyl complexes of tris-carbene borate ligands which adopt rare seesaw geometries. Experimental and computational results suggest the structural distortion from threefold symmetry results from a combination of electronic stabilization of the singlet state, strong field donors, and constrained angles from the chelating ligand.

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

Comparative differential cuproproteomes of Rhodobacter capsulatus reveal novel copper homeostasis related proteins

Abstract Copper (Cu) is an essential, but toxic, micronutrient for living organisms and cells have developed sophisticated response mechanisms towards both the lack and the excess of Cu in their environments. In this study, we achieved a global view of Cu-responsive changes in the prokaryotic model organism Rhodobacter capsulatus using label-free quantitative differential proteomics. Semi-aerobically grown cells under heterotrophic conditions in minimal medium (∼0.3 μM Cu) were compared with cells supplemented with either 5 μM Cu or with 5 mM of the Cu-chelator bathocuproine sulfonate. Mass spectrometry based bottom-up proteomics of unfractionated cell lysates identified 2430 of the 3632 putative proteins encoded by the genome, producing a robust proteome dataset for R. capsulatus. Use of biological and technical replicates for each growth condition yielded high reproducibility and reliable quantification for 1926 of the identified proteins. Comparison of cells grown under Cu-excess or Cu-depleted conditions to those grown under minimal Cu-sufficient conditions revealed that 75 proteins exhibited statistically significant (p < 0.05) abundance changes, ranging from 2- to 300-fold. A subset of the highly Cu-responsive proteins was orthogonally probed using molecular genetics, validating that several of them were indeed involved in cellular Cu homeostasis.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Evaluating aqueous flow battery electrolytes: a coordinated approach

Here, we outline some basic pitfalls in the electrochemical investigation of aqueous metal complexes and advocate for the use of bulk electrolysis in redox flow cells for electrolyte analysis. We demonstrate the methods of operation and performance of a lab scale redox flow battery (RFB), which is assembled from unmodified, commercially available material and cycled with a vanadium electrolyte in order to provide a comparative baseline of expected performance. Common misconceptions about the thermodynamic window for water splitting are addressed and further express the need to develop next-generation aqueous redox flow battery electrolytes. Although non-aqueous electrolytes are a popular approach, they suffer from distinct challenges that limit energy and power density in comparison with aqueous electrolytes. Expanding the scope of aqueous electrolytes to include metal–chelate complexes allows electrolytes to be as tailorable as organic species, while maintaining robust metal-based redox processes. A flow battery assembly and operation guide is provided to help facilitate the use of flow battery testing in the evaluation of next-generation electrolytes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Synthesis, characterization, and polymerization of capped paddlewheel porous cages

Although paddlewheel-based structures are common among permanently porous metal–organic materials, suitable strategies for the isolation of metal node-terminated, capped paddlewheel-based cage structures remain limited. We explored the use of chelating dicarboxylate ligand derivates (esp) for the isolation of trimesate-linked cages, Mo 12 (btc) 4 (esp) 6 , that are structural analogs of the small octahedral pore of HKUST-1. The porosity of these novel cages is appreciably higher than that of previously reported structures of this type. We also demonstrate that pillaring the isolated cage with DABCO generated an amorphous polymer that featured exceptional thermal stability and enhanced porosity.

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

PBT2 acts through a different mechanism of action than other 8-hydroxyquinolines: an X-ray fluorescence imaging study

8-Hydroxyquinolines (8HQs) comprise a family of metal-binding compounds that have been used or tested for use in numerous medicinal applications, including as treatments for bacterial infection, Alzheimer's disease, and cancer. Two key 8HQs, CQ (5-chloro-7-iodo-8-hydroxyquinoline) and PBT2 (2-(dimethylamino)methyl-5,7-dichloro-8-hydroxyquinoline), have drawn considerable interest and have been the focus of many studies investigating their in vivo properties. These drugs have been described as copper and zinc ionophores because they do not cause metal depletion, as would be expected for a chelation mechanism, but rather cellular accumulation of these ions. In studies of their anti-cancer properties, CQ has been proposed to elicit toxic intracellular copper accumulation and to trigger apoptotic cancer cell death through several possible pathways. In this study we used synchrotron X-ray fluorescence imaging, in combination with biochemical assays and light microscopy, to investigate 8HQ-induced alterations to metal ion homeostasis, as well as cytotoxicity and cell death. We used the bromine fluorescence from a bromine labelled CQ congener (5,7-dibromo-8-hydroxyquinoline; B2Q) to trace the intracellular localization of B2Q following treatment and found that B2Q crosses the cell membrane. We also found that 8HQ co-treatment with Cu(ii) results in significantly increased intracellular copper and significant cytotoxicity compared with 8HQ treatments alone. PBT2 was found to be more cytotoxic, but a weaker Cu(ii) ionophore than other 8HQs. Moreover, treatment of cells with copper in the presence of CQ or B2Q resulted in copper accumulation in the nuclei, while PBT2-guided copper was distributed near to the cell membrane. Furthermore, these results suggest that PBT2 may be acting through a different mechanism than that of other 8HQs to cause the observed cytotoxicity.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Predicting 1 H NMR relaxation in Gd 3+ -aqua using molecular dynamics simulations

Atomistic molecular dynamics simulations are used to predict 1 H NMR T 1 relaxation of water from paramagnetic Gd 3+ ions in solution at 25 °C. Simulations of the T 1 relaxivity dispersion function r 1 computed from the Gd 3+ – 1 H dipole–dipole autocorrelation function agree within ≃8% of measurements in the range f 0 ≃ 5 ↔ 500 MHz, without any adjustable parameters in the interpretation of the simulations, and without any relaxation models. Here the simulation results are discussed in the context of the Solomon-Bloembergen-Morgan inner-sphere relaxation model, and the Hwang-Freed outer-sphere relaxation model. Below f 0 ≲ 5 MHz, the simulation overestimates r 1 compared to measurements, which is used to estimate the zero-field electron-spin relaxation time. The simulations show potential for predicting r 1 at high frequencies in chelated Gd 3+ contrast-agents used for clinical MRI.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Mechanochemical synthesis and structural analysis of trivalent lanthanide and uranium diphenylphosphinodiboranates

Phosphinodiboranates (H 3 BPR 2 BH 3 – ) are a class of borohydrides that have merited a reputation as weakly coordinating anions, which is attributed in part to the dearth of coordination complexes known with transition metals, lanthanides, and actinides. We recently reported how K(H 3 BP t Bu 2 BH 3 ) exhibits sluggish salt elimination reactivity with f-metal halides in organic solvents such as Et 2 O and THF. Here we report how this reactivity appears to be further attenuated in solution when the t Bu groups attached to phosphorus are exchanged for R = Ph or H, and we describe how mechanochemistry was used to overcome limited solution reactivity with K(H 3 BPPh 2 BH 3 ). Grinding three equivalents of K(H 3 BPPh 2 BH 3 ) with UI 3 (THF) 4 or LnI 3 (Ln = Ce, Pr, Nd) allowed homoleptic complexes with the empirical formulas U(H 3 BPPh 2 BH 3 ) 3 (1), Ce(H 3 BPPh 2 BH 3 ) 3 (2), Pr(H 3 BPPh 2 BH 3 ) 3 (3), and Nd(H 3 BPPh 2 BH 3 ) 3 (4) to be prepared and subsequently crystallized in good yields (50–80%). Single-crystal XRD studies revealed that all four complexes exist as dimers or coordination polymers in the solid-state, whereas 1 H and 11 B NMR spectra showed that they exist as a mixture of monomers and dimers in solution. Treating 4 with THF breaks up the dimer to yield the monomeric complex Nd(H 3 BPPh 2 BH 3 ) 3 (THF) 3 (4-THF). XRD studies revealed that 4-THF has one chelating and two dangling H 3 BPPh 2 BH 3 – ligands bound to the metal to accommodate binding of THF. In contrast to the results with K(H 3 BPPh 2 BH 3 ), attempting the same mechanochemical reactions with Na(H 3 BPH 2 BH 3 ) containing the simplest phosphinodiboranate were unsuccessful; only the partial metathesis product U(H 3 BPH 2 BH 3 )I 2 (THF) 3 (5) was isolated in poor yields. Here, despite these limitations, our results offer new examples showing how mechanochemistry can be used to rapidly synthesize molecular coordination complexes that are otherwise difficult to prepare using more traditional solution methods.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Mechanistic investigation of the aerobic oxidation of 2-pyridylacetate coordinated to a Ru(ii) polypyridyl complex

A new ruthenium polypyridyl complex, [Ru(bpy) 2 (acpy)] + (acpy = 2-pyridylacetate, bpy = 2,2'-bipyridine), was synthesized and fully characterized. Distinct from the previously reported analog, [Ru(bpy) 2 (pic)] + (pic = 2-pyridylcarboxylate), the new complex is unstable under aerobic conditions and undergoes oxidation to yield the corresponding α-keto-2-pyridyl-acetate (acpyoxi) coordinated to the Ru II center. The reaction is one of the few examples of C–H activation at mild conditions using O 2 as the primary oxidant and can provide mechanistic insights with important implications for catalysis. Theoretical and experimental investigations of this aerobic oxidative transformation indicate that it takes place in two steps, first producing the α-hydroxo-2-pyridyl-acetate analog and then the final product. The observed rate constant for the first oxidation was in the order of 10 -2 h -1 . The reaction is hindered in the presence of coordinating solvents indicating the role of the metal center in the process. Theoretical calculations at the M06-L level of theory were performed for multiple reaction pathways in order to gain insights into the most probable mechanism. Our results= indicate that O 2 binding to [Ru(bpy) 2 (acpy)] + is favored by the relative instability of the six-ring chelate formed by the acpy ligand and the resulting Ru III -OO˙- superoxo is stabilized by the carboxylate group in the coordination sphere. C–H activation by this species involves high activation free energies (ΔG ‡ = 41.1 kcal mol -1 ), thus the formation of a diruthenium μ-peroxo intermediate, [(Ru III (bpy) 2 (O-acpy)) 2 O 2 ] 2+ via interaction of a second [Ru(bpy) 2 (acpy)] + was examined as an alternative pathway. The dimer yields two Ru IV =O centers with a low ΔG ‡ of 2.3 kcal mol -1 . The resulting Ru IV =O species can activate C–H bonds in acpy (ΔG ‡ = 23.1 kcal mol -1 ) to produce the coordinated α-hydroxo-2-pyridylacetate. Further oxidation of this intermediate leads to the α-keto-2-pyridyl-acetate product. The findings provide new insights into the mechanism of C–H activation catalyzed by transition-metal complexes using O 2 as the sole oxygen source.

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

Metal-hydrogen-pi-bonded organic frameworks

We report the synthesis and characterization of a new series of permanently porous, three-dimensional metal–organic frameworks (MOFs), M-HAF-2 (M = Fe, Ga, or In), constructed from tetratopic, hydroxamate-based, chelating linkers. Here, the structure of M-HAF-2 was determined by three-dimensional electron diffraction (3D ED), revealing a unique interpenetrated hcb-a net topology. This unusual topology is enabled by the presence of free hydroxamic acid groups, which lead to the formation of a diverse network of cooperative interactions comprising metal–hydroxamate coordination interactions at single metal nodes, staggered π–π interactions between linkers, and H-bonding interactions between metal-coordinated and free hydroxamate groups. Such extensive, multimodal interconnectivity is reminiscent of the complex, noncovalent interaction networks of proteins and endows M-HAF-2 frameworks with high thermal and chemical stability and allows them to readily undergo postsynthetic metal ion exchange (PSE) between trivalent metal ions. We demonstrate that M-HAF-2 can serve as versatile porous materials for ionic separations, aided by one-dimensional channels lined by continuously π-stacked aromatic groups and H-bonding hydroxamate functionalities. As an addition to the small group of hydroxamic acid-based MOFs, M-HAF-2 represents a structural merger between MOFs and hydrogen-bonded organic frameworks (HOFs) and illustrates the utility of non-canonical metal-coordinating functionalities in the discovery of new bonding and topological patterns in reticular materials.

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

Anion-induced disproportionation of Th( iii ) complexes to form Th( ii ) and Th( iv ) products

Here, a new synthesis of Th(II) complexes has been identified involving addition of simple MX salts (M = Li, Na, K; X = H, Cl, Me, N 3 ) to Cp" 3 Th III [Cp" = [C 5 H 3 (SiMe 3 ) 2 ] in the presence of 18-crown-6 or 2.2.2-cryptand, forming [M(chelate)][Cp" 3 Th II ] and Cp'' 3 Th IV X. Cp tet 3 Th III (Cp tet = C 5 Me 4 H) reacts with KH to form Cp tet 3 Th IV H and the C–H bond activation product, [K(crypt)]{[Cp tet 2 Th IV H[η 1 :η 5 -C 5 Me 3 H(CH 2 )]}.

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

Pressurized formic acid dehydrogenation: an entropic spring replaces hydrogen compression cost

Formic acid is unique among liquid organic hydrogen carriers (LOHCs), because its dehydrogenation is highly entropically driven. This enables the evolution of high-pressure hydrogen at mild temperatures that is difficult to achieve with other LOHCs, conceptually by releasing the “spring” of energy stored entropically in the liquid carrier. Applications calling for hydrogen-on-demand, such as vehicle filling, require pressurized H 2 . Hydrogen compression dominates the cost for such applications, yet there are very few reports of selective, catalytic dehydrogenation of formic acid at elevated pressure. Herein, we show that homogenous catalysts with various ligand frameworks, including Noyori-type tridentate (PNP, SNS, SNP, SNPO), bidentate chelates (pyridyl)NHC, (pyridyl)phosphine, (pyridyl)sulfonamide, and their metallic precursors, are suitable catalysts for the dehydrogenation of neat formic acid under self-pressurizing conditions. Quite surprisingly, we discovered that their structural differences can be related to performance differences in their respective structural families, with some tolerant or intolerant of pressure and others that are significantly advantaged by pressurized conditions. Here, we further find important roles for H 2 and CO in catalyst activation and speciation. In fact, for certain systems, CO behaves as a healing reagent when trapped in a pressurizing reactor system, enabling extended life from systems that would be otherwise deactivated.

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

BODIPY and dipyrrin as unexpected robust anchoring groups on TiO 2 nanoparticles

Covalent attachment of molecules to metal oxide surfaces typically demands the presence of an anchoring group that in turn requires synthetic steps to introduce. BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) chromophores have long been used in dye-sensitized solar cells, but carboxylic acid groups typically had to be installed to act as surface anchors. We now find that even without the introduction of such anchors, the unmodified BODIPY can bind to TiO 2 surfaces via its BF 2 group through boron–oxygen surface bonds. Dipyrrin, the parent molecule of BODIPY, is also capable of binding directly to TiO 2 surfaces, likely through its chelating nitrogen atoms. These binding modes prove to be even more robust than that of an installed carboxylate and offer a new way to attach molecular complexes to surfaces for (photo)catalytic applications since, once bound, we show that surface bound BODIPY and dipyrrin derivatives exhibit ultrafast photoinjection of electrons into the conduction band of TiO 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Trimethyltriazacyclohexane coordination chemistry of simple rare-earth metal salts

Reactions of 1,3,5-trimethyl-triazacyclohexane (Me 3 tach) with common rare-earth metal iodide, chloride, and triflate salts were examined to determine the capacity of this inexpensive chelate to provide alternative precursors for THF-free reactions. The reaction of LaI 3 (THF) 4 and CeI 3 (THF) 4 with 1,3,5-trimethyl-triazacyclohexane in THF generated toluene soluble (Me 3 tach) 2 LnI 3 , 1-Ln , in which the Ln center has a tri-capped trigonal prismatic geometry with two eclipsed Me 3 tach rings. Reaction with NdI 3 (THF) 3.5 forms the analogous 1-Nd , but a different structure with one outer sphere iodide, [(Me 3 tach) 2 NdI 2 ][I], 2-Nd , is also accessible and has a structure reminiscent of bent metallocenes. The reaction of LaCl 3 and Me 3 tach forms the less soluble (Me 3 tach) 2 LaCl 3 , which has a structure analogous to 1-Ln with eclipsed Me 3 tach rings. The mono-ring yttrium complex, (Me 3 tach)YCl 3 (THF) 2 , could be isolated from the reaction of YCl 3 with Me 3 tach. Reactions of La(OTf) 3 with Me 3 tach were sensitive to the presence of residual proton sources as exemplified by the isolation of {[(Me 3 tach)La(μ-OH)(μ-OTf)] 2 (μ-OTf) 2 } 2 , 5-La , and [HMe 3 tach][(Me 3 tach) 2 La-(OTf) 4 ], 6-La . SmI 2 reacts with Me 3 tach to produce the Sm( II ) complex, (Me 3 tach) 2 SmI 2 (THF), 7-Sm , but 2-Sm can also form in this reaction. Complexes of the larger 1,4,7-trimethyltriazacyclononane (Me 3 tacn) ligand, namely (Me 3 tacn)LaI 3 (THF), (Me 3 tacn)YCl 3 , and (Me 3 tacn)SmI 2 (THF) were synthesized for comparison. Several examples of the protonated ligands with simple counteranions, [HMe 3 tach][X] (X = Cl, Br, I) and [HMe 3 tacn][OTf], were identified in the course of these studies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗