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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Synthesis of Two New Group 13 Benzoato-Chloro Complexes: A Structural Study of Gallium and Indium Chelating Carboxylates

Two new heteroleptic chelated-benzoato gallium (III) and indium (III) complexes have been prepared and structurally characterized. The molecular structures of [GaCl2(4-Mepy)2(O2CPh)]4-Mepy (1) and [InCl(4-Mepy)2(O2CPh)2]4-Mepy (2) have been determined by single-crystal x-ray diffraction. The gallium compound (1) is a distorted octahedron with cis-chloride ligands co-planar with the chelating benzoate and the 4-methylpyridines trans to each other. This is the first example of a Ga(III) structure with a chelating benzoate. The indium compound (2) is a distorted pentagonal bipyramid with two chelating benzoates, one 4-methylpyridine in the plane and a chloride trans to the other 4-methylpyridine. The indium bis-benzoate is an unusual example of a seven-coordinate structure with classical ligands. Both complexes, which due to the chelates, could also be described as pseudo-trigonal bipyramidal, include a three-bladed motif with three roughly parallel aromatic rings that along with a solvent of crystallization and electron-withdrawing chloride ligand(s) stabilize the solid-state structures.

Duraj, Stan A.↗
DOE OSTI2023

Impact of a Biological Chelator, Lanmodulin, on Minor Actinide Aqueous Speciation and Transport in the Environment

Minor actinides are major contributors to the long-term radiotoxicity of nuclear fuels and other radioactive wastes. Here in this context, understanding their interactions with natural chelators and minerals is key to evaluating their transport behavior in the environment. The lanmodulin family of metalloproteins is produced by ubiquitous bacteria and Methylorubrum extorquens lanmodulin (LanM) was recently identified as one of nature’s most selective chelators for trivalent f-elements. Herein, we investigated the behavior of neptunium, americium, and curium in the presence of LanM, carbonate ions, and common minerals (calcite, montmorillonite, quartz, and kaolinite). We show that LanM’s aqueous complexes with Am(III) and Cm(III) remain stable in carbonate-bicarbonate solutions. Furthermore, the sorption of Am(III) to these minerals is strongly impacted by LanM, while Np(V) sorption is not. With calcite, even a submicromolar concentration of LanM leads to a significant reduction in the Am(III) distribution coefficient (K d , from >10 4 to ~10 2 mL/g at pH 8.5), rendering it even more mobile than Np(V). Thus, LanM-type chelators can potentially increase the mobility of trivalent actinides and lanthanide fission products under environmentally relevant conditions. Monitoring biological chelators, including metalloproteins, and their biogenerators should therefore be considered during the evaluation of radioactive waste repository sites and the risk assessment of contaminated sites.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Synthesis and Evaluation of a Bifunctional Chelator for Thorium-227 Targeted Radiotherapy

Thorium-227 (227Th) is an α-emitting radionuclide currently under investigation for targeted alpha therapy. Available chelators used for this isotope suffer from challenging multistep syntheses. Here, we present the synthesis and preclinical evaluation of a novel bifunctional chelator, p-SCN-Bn-DOTHOPO, which contains an isothiocyanate group that is suitable for conjugation to biological molecules. This bifunctional chelator was prepared with a 26% overall yield in four steps and conjugated to the human epidermal growth factor receptor 2 targeting antibody, trastuzumab. The resulting immunoconjugate was labeled with [227Th]ThIV (pH 5.5, room temperature, 60 min) with ≥95% radiochemical yield and purity. The conjugate was also labeled with zirconium-89 (89Zr), which can be used for positron emission tomography imaging. The radiometal complexes were subsequently investigated for their biological stability. The results described here provide insight into ligand design strategies and optimization of chelators for the development of the next generation of 89Zr and 227Th radiopharmaceuticals.

Thorium↗
DOE OSTI2023

Chelation Model Validation: Modeling of a Plutonium-238 Inhalation Incident Treated with DTPA at Los Alamos National Laboratory

Accidental inhalation of plutonium at the workplace is a non-negligible risk, even when rigorous safety standards are in place. The intake and retention of plutonium in the human body may be a source of concern. Thus, if there is a suspicion of a significant intake of plutonium, medical countermeasures such as chelation treatment may be administered to the worker. The present work aimed to interpret the bioassay data of a worker involved in an inhalation incident due to a glovebox breach at Los Alamos National Laboratory’s plutonium facility. The worker was treated with intravenous injections of calcium salts of diethylenetriaminepentaacetic acid (DTPA) in an attempt to reduce the amount of plutonium from the body and therefore reduce the internal radiation dose. It is well known in the internal dosimetry field that the administration of chelation treatment poses additional challenges to the dose assessment. Hence, a recently developed chelation model was used for the modeling of the bioassay data. The objectives of this work are to describe the incident, model the chelation-affected and non-affected bioassay data, estimate the plutonium intake, and assess the internal radiation dose.

238Pu↗
DOE OSTI2022

Chelating platform for delivery of radionuclides

Siderocalin-metal chelator combinations that bind metallic radioisotopes used in nuclear medicine with high affinity are described. The high affinity siderocalin-metal chelator combinations include a number of chelator backbone arrangements with functional groups that coordinate with metals. The siderocalin-metal chelator combinations can be used to deliver radionuclides for imaging and therapeutic purposes.

Strong, Roland K.↗
DOE OSTI2025

Towards the Stable Chelation of Radioantimony(V) for Targeted Auger Theranostics

Antimony-119 ( 119 Sb) is one of the most attractive Auger-electron emitters identified to date, but it remains practically unexplored for targeted radiotherapy because no chelators have been identified to stably bind this metalloid in vivo. In a departure from current studies focused on chelator development for Sb(III), we explore the chelation chemistry of Sb(V) using the tris-catecholate ligand TREN-CAM. Through a combination of radiolabeling, spectroscopic, solid-state, and computational studies, the radiochemistry and structural chemistry of TREN-CAM with 1XX/nat Sb(V) were established. The resulting [ 1XX Sb]Sb–TREN-CAM complex remained intact for several days in human serum, signifying high stability under biological conditions. Finally, the first in vivo single photon emission computed tomography and positron emission tomography imaging studies were carried out using 117 Sb, the diagnostic analogue of 119 Sb. These studies revealed marked differences in the uptake and distribution of activity in mice administered unchelated [ 117 Sb]Sb(OH) 6 – versus [ 117 Sb]Sb–TREN-CAM, suggesting that 117 Sb is largely retained by TREN-CAM over the time course of the study. Collectively, these findings demonstrate the most physiologically stable complex of no-carrier-added 1XX Sb yet reported, offering new promise for the clinical implementation of radioantimony in nuclear medicine. In conclusion, our results also establish the feasibility of 117 Sb as an elementally matched partner to 119 Sb for theranostic applications.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2024

Chelation-directed interface engineering of in-place self-cleaning membranes

Water–energy sustainability will depend upon the rapid development of advanced pressure-driven separation membranes. Although energy-efficient, water-treatment membranes are constrained by ubiquitous fouling, which may be alleviated by engineering self-cleaning membrane interfaces. In this study, a metal-polyphenol network was designed to direct the armorization of catalytic nanofilms (ca. 18 nm) on inert polymeric membranes. The chelation-directed mineralized coating exhibits high polarity, superhydrophilicity, and ultralow adhesion to crude oil, enabling cyclable crude oil-in-water emulsion separation. The in-place flux recovery rate exceeded 99.9%, alleviating the need for traditional ex situ cleaning. The chelation-directed nanoarmored membrane exhibited 48-fold and 6.8-fold figures of merit for in-place self-cleaning regeneration compared to the control membrane and simple hydraulic cleaning, respectively. Precursor interaction mechanisms were identified by density functional theory calculations. Here, chelation-directed armorization offers promise for sustainable applications in catalysis, biomedicine, environmental remediation, and beyond.

42 ENGINEERING↗
DOE OSTI2025

Towards the Stable Chelation of Radioantimony(V) for Targeted Auger Theranostics

Abstract Antimony‐119 ( 119 Sb) is one of the most attractive Auger‐electron emitters identified to date, but it remains practically unexplored for targeted radiotherapy because no chelators have been identified to stably bind this metalloid in vivo. In a departure from current studies focused on chelator development for Sb(III), we explore the chelation chemistry of Sb(V) using the tris‐catecholate ligand TREN‐CAM. Through a combination of radiolabeling, spectroscopic, solid‐state, and computational studies, the radiochemistry and structural chemistry of TREN‐CAM with 1XX/nat Sb(V) were established. The resulting [ 1XX Sb]Sb–TREN‐CAM complex remained intact for several days in human serum, signifying high stability under biological conditions. Finally, the first in vivo single photon emission computed tomography and positron emission tomography imaging studies were carried out using 117 Sb, the diagnostic analogue of 119 Sb. These studies revealed marked differences in the uptake and distribution of activity in mice administered unchelated [ 117 Sb]Sb(OH) 6 – versus [ 117 Sb]Sb–TREN‐CAM, suggesting that 117 Sb is largely retained by TREN‐CAM over the time course of the study. Collectively, these findings demonstrate the most physiologically stable complex of no‐carrier‐added 1XX Sb yet reported, offering new promise for the clinical implementation of radioantimony in nuclear medicine. Our results also establish the feasibility of 117 Sb as an elementally matched partner to 119 Sb for theranostic applications.

Olson, Aeli P. [Department of Medical Physics Univ↗
DOE OSTI2023

Development of LpxH Inhibitors Chelating the Active Site Dimanganese Metal Cluster of LpxH

Abstract Despite the widespread emergence of multidrug‐resistant nosocomial Gram‐negative bacterial infections and the major public health threat it brings, no new class of antibiotics for Gram‐negative pathogens has been approved over the past five decades. Therefore, there is an urgent medical need for developing effective novel antibiotics against multidrug‐resistant Gram‐negative pathogens by targeting previously unexploited pathways in these bacteria. To fulfill this crucial need, we have been investigating a series of sulfonyl piperazine compounds targeting LpxH, a dimanganese‐containing UDP‐2,3‐diacylglucosamine hydrolase in the lipid A biosynthetic pathway, as novel antibiotics against clinically important Gram‐negative pathogens. Inspired by a detailed structural analysis of our previous LpxH inhibitors in complex with K. pneumoniae LpxH ( Kp LpxH), here we report the development and structural validation of the first‐in‐class sulfonyl piperazine LpxH inhibitors, JH‐LPH‐45 ( 8 ) and JH‐LPH‐50 ( 13 ), that achieve chelation of the active site dimanganese cluster of Kp LpxH. The chelation of the dimanganese cluster significantly improves the potency of JH‐LPH‐45 ( 8 ) and JH‐LPH‐50 ( 13 ). We expect that further optimization of these proof‐of‐concept dimanganese‐chelating LpxH inhibitors will ultimately lead to the development of more potent LpxH inhibitors for targeting multidrug‐resistant Gram‐negative pathogens.

Pharmacology & Pharmacy↗
DOE OSTI2020

Selective Lanthanide Sensing with Gold Nanoparticles and Hydroxypyridinone Chelators

The octadentate hydroxypyridinone chelator 3,4,3-LI(1,2-HOPO) is a promising therapeutic agent because of its high affinity for f-block elements and noncytotoxicity at medical dosages. The interaction between 3,4,3-LI(1,2-HOPO) and other biomedically relevant metals such as gold, however, has not been explored. Gold nanoparticles functionalized with chelators have demonstrated great potential in theranostics, yet thus far, no protocol that combines 3,4,3-LI(1,2-HOPO) and colloidal gold has been developed. Here, we characterize the solution thermodynamic properties of the complexes formed between 3,4,3-LI(1,2-HOPO) and Au 3+ ions and demonstrate how under specific pH conditions the chelator promotes the growth of gold nanoparticles, acting as both reducing and stabilizing agent. 3,4,3-LI(1,2-HOPO) ligands on the nanoparticle surface remain active and selective toward f-block elements, as evidenced by gold nanoparticle selective aggregation. Finally, a new colorimetric assay capable of reaching the detection levels necessary for the quantification of lanthanides in waste from industrial processes is developed based on the inhibition of particle growth by lanthanides.

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

Polymer Tacticity Effects in Polymer–Lanthanide Chelation Thermodynamics

Metal-chelating polymers are critical components in numerous applications. However, despite the known influence of polymer tacticity on both bulk and solution properties, most materials used in metal-chelation applications are atactic. Here, we investigate the relationship between polymer tacticity and polymer–lanthanide interactions in aqueous solution. We synthesized a series of five poly(methacrylic acid)s with systematic variations in tacticity (20–99% m diads) and used isothermal titration calorimetry to measure the thermodynamics of lanthanide binding to each material (ΔH, ΔG, ΔS, K a , and stoichiometry). We observed enthalpy–entropy compensation across this tacticity series, finding that both |ΔH| and |ΔS| decreased with decreasing m diad content while ΔG remained similar. Molecular dynamics simulations of the polymer–metal interactions revealed that the observed differences in binding thermodynamics may be largely ascribed to differences in polymer flexibility. Furthermore, these combined experimental and computational results demonstrate that metal binding can be influenced by altering the polymer stereochemistry, ultimately influencing the design of more efficient metal-chelating materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Chelation-Driven Chemistry Controls Dissolution Pathways for Facile Critical Mineral Recovery from Ultramafic Resources

The efficient recovery of critical minerals, such as nickel (Ni) and manganese (Mn) from the subsurface is of vital importance, given their role in modern technologies ranging from batteries to advanced alloys. This study explores an approach that employs chelation to enhance critical mineral recovery from ultramafic rocks using chelating ligands under ambient pressures and systematically evaluates the extraction process for the first time. Experimental results demonstrate the superior performance of EDTA and PrDTA in achieving high extraction efficiencies for both Ni and Mn. To further highlight the ability for optimization, the fluid exchange and variation of fluid-to-rock ratio experiments were conducted, revealing tunable controls for engineering recovery. We show that under optimized conditions, a Ni extraction efficiency of ?82% and a Mn extraction efficiency of ~60% is achieved at ambient pressures, which is equivalent to over 23 times the current global Ni production, and 2 million metric tonnes (MMT) greater than the current global Mn production. From both in-situ and ex-situ mining perspectives, the results highlight the potential of chelation to advance sustainable mineral processing. Overall, this work highlights the environmental benefits of innovative ligand-assisted recovery methods, addressing the critical need for the efficient utilization of olivine resources.

Krishnan, Keerthana↗
DOE OSTI2026

Luminescent N-heterocyclic carbene Cu( I ) complexes with N^O chelating ligands exhibit microsecond lifetimes and photocatalytic activity

To replace precious noble metal-based photosensitizers in applications involving photoinduced charge separation, energy transfer, or photocatalysis, Cu(I) complexes are considered to be cost-effective, earth-abundant, and sustainable alternatives. An emerging and effective design principle in Cu(I) photosensitizers involves heteroleptic structures where the HOMO and LUMO are spatially separated over two different ligands. In the present work, we introduce a complementary class of heteroleptic, three-coordinate copper photosensitizers that pairs variable N^O chelating ligands (8-hydroxyquinoline and 10-hydroxybenzo[h]quinoline) with a bulky 2,6-diisopropylphenyl-substituted N-heterocyclic carbene (NHC). In this design, both frontier orbitals are localized on the same ligand, the N^O chelate, such that structural modulation of the electron-rich N^O-chelates can substantially tune the energy levels of the HOMO and LUMO, thereby controlling the photoluminescence properties. Detailed photophysical and electrochemical experiments as well as DFT calculations suggest charge-transfer transitions with intra-ligand charge transfer (ILCT) character, involving the N^O ligands. This strategy successfully produced long triplet excited-state lifetimes (up to 44 µs) in compounds that are strong photoreductants (E([Cu] + /*[Cu] as negative as −2.0 V vs. the ferrocenium/ferrocene couple). These properties allow these photosensitizers to be used as photocatalysts in various transformations of organic compounds, such as hydrogenation of substituted benzophenones, hydrodehalogenation of aryl/alkyl halides (including challenging C–Cl bond activation) and E/Z isomerization of (E)-stilbene (an example of triplet–triplet energy transfer).

Chakraborty, Soumi [University of Houston, TX (Uni↗
NASA NTRS1996

Analysis of Supercritical-Extracted Chelated Metal Ions From Mixed Organic-Inorganic Samples

Organic and inorganic contaminants of an environmental sample are analyzed by the same GC-MS instrument by adding an oxidizing agent to the sample to oxidize metal or metal compounds to form metal ions. The metal ions are converted to chelate complexes and the chelate complexes are extracted into a supercritical fluid such as CO2. The metal chelate extract after flowing through a restrictor tube is directly injected into the ionization chamber of a mass spectrometer, preferably containing a refractory metal filament such as rhenium to fragment the complex to release metal ions which are detected. This provides a fast, economical method for the analysis of metal contaminants in a sample and can be automated. An organic extract of the sample in conventional or supercritical fluid solvents can be detected in the same mass spectrometer, preferably after separation in a supercritical fluid chromatograph.

Sinha, Mahadeva P.↗
DOE OSTI2022

Determination of transition metal ions in fossil fuel associated wastewaters using chelation ion chromatography

Here, this study outlines the development and subsequent validation of a method using chelation ion chromatography (CIC) pretreatment followed by traditional ion chromatography (IC) and post column UV/vis detection to measure transition metals in fossil fuel wastewaters, such as oil & gas (O&G) brines and coal mine drainage (CMD) waters. Measurement of transition metals is often an important characterization step in the research of environmental and energy systems. IC represents one way to measure these metals with the advantages of being versatile, simple and relatively low cost compared to other analytical methods. However, high concentrations of alkali and alkaline earth metals present in fossil fuel wastewaters will decrease IC detectability of transition metals in these waters. In this study, a CIC method was developed for the analysis of transition metal ions (Fe 3+ , Cu 2+ , Ni 2+ , Zn 2+ , Co 2+ , Mn 2+ , and Fe 2+ ) in fossil fuel associated wastewaters such as Appalachian CMD and O&G wastewaters from the Permian and Bakken shale basins in the United States. CIC system incorporated an on-line chelator column (e.g., the MetPac CC-1) with high selectivity for transition metals over alkali and alkaline earth metals for salt matrix removal prior to transition metal separation and detection. Additional method developments also included acidifying all samples to 2% v/v HCl and using gradient elution rather than isocratic. The recoverability of transition metals in simple salt solutions commonly found in CMD and brine samples (e.g. NaCl, Na 2 SO 4 , CaCl 2 ) using CIC was evaluated and compared to that using traditional IC. Our results found that the CIC system significantly improved transition metal recoveries for samples in 10,000 mg/L CaCl 2 matrix, reaching 87%-108% recovery for all analytes, as opposed to 2-323% recovery in traditional IC. The limits of detection in this study achieved 10.09 – 161.2 μg/L, comparable to reported values in similar IC studies. The developed method was also verified with certified water samples, resulting in 89% - 111% recoveries in samples with higher analyte concentrations (i.e. >4x the LoDs). The developed method achieved 87% -112% recoveries for most analytes in CMD samples and 72%-138% recoveries for Bakken shale samples, relative to ICP-MS values. Overall, the current IC method can be a very good screening tool for fast and cheap analysis for transition metals at mg/L level, to facilitate selection of samples for more detailed ICP-MS analysis.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2025

Structure–Function Relationships in Sequence-Controlled Copolymers for Rare Earth Element Chelation

The ability to tune material function through primary sequence is a defining feature of biological macromolecules, allowing precise control over structure and target interactions in complex aqueous environments. However, translating sequence–structure–function relationships to synthetic macromolecules is challenging due to their dispersity in sequence, conformation, and composition. Here, we report systematic studies of amphiphilic polymer chelators designed to probe how composition and patterning influence binding affinity and selectivity for rare earth elements (REEs), a series of technologically relevant metals with challenging separation profiles. A library of copolymers varying hydrophobic monomer composition and patterning was synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization, spanning statistical, gradient, and block architectures. REE binding was quantified using a high-throughput colorimetric assay, and reconstruction of polymer ensembles using kinetic stochastic simulations enabled quantitative comparisons of sequence heterogeneity, linking local monomer colocalization to emergent REE binding. Further, we investigated the role of different hydrophobic comonomers in tuning metal coordination, with binding trends linked to structural features that influence binding site desolvation. Complementary dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) measurements showed that both polymer and monomer architecture modulate metal-induced conformational changes, and that multichain assembly behavior emerges beyond critical hydrophobic thresholds. Sequence control also altered REE selectivity, with nonmonotonic differences observed across compositionally identical polymers with different sequence architectures. Together, these findings establish design principles that connect polymer sequence and structure to binding performance, guiding the design of macromolecular chelators with enhanced affinity and selectivity for applications in separations, sensing, and catalysis.

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

Unimodal Imaging of Monovalent Metal-Chelator Complexes and Lipids by MALDI Imaging Mass Spectrometry

Careful regulation of monovalent metal ions (M + ) is necessary to maintain a functional cellular system. Of these ions, appropriate sodium (Na + ) and potassium (K + ) concentrations are particularly integral for electrochemical signaling, as well as the secondary transport of nutrients and waste. Dysregulation of M + homeostasis can disrupt these mechanisms, potentially influencing the metabolism of downstream biomolecules such as lipids. Thus, the relationship between M + abundances and related biomolecular distributions must be elucidated to better understand the physiology of healthy and disordered tissues. Traditional techniques for imaging biological metal distributions include SIMS, LA-ICP-MS, and XRF; however, these capabilities are limited to elemental analysis or the analysis of molecular fragments and must be paired with other modalities to visualize distributions of more complex biomolecules within the same or similar samples. Conversely, matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) is a powerful tool often used for mapping such biomolecular distributions, but current methods are unable to detect metals within tissue. This study illustrates a novel methodology that adds metal detection to the MALDI IMS repertoire through which the simultaneous detection of M + metals and lipids is achievable. Using a robotic sprayer for homogeneous application, on-tissue deposition of the chelator deferiprone (DEF) enables subsequent detection of the ionizable metal-chelator complex by MALDI without hindering lipid detection. Our work provides proof-of-concept data for the simultaneous detection of K + , Na + , and intact lipids using MALDI IMS.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Tuning aminopolycarboxylate chelators for efficient complexation of trivalent actinides

The complexation of trivalent lanthanides and minor actinides (Am 3+ , Cm 3+ , and Cf 3+ ) by the acyclic aminopolycarboxylate chelators 6,6'-((ethane-1,2-diylbis–((carboxymethyl)azanediyl))bis–(methylene))dipicolinic acid (H 4 octapa) and 6,6'-((((4-(1-(2-(2-(2-hydroxyethoxy)ethoxy)ethyl)-1H-1,2,3-triazol-4-yl)pyridine-2,6-diyl)bis–(methylene))bis–((carboxymethyl)azanediyl))bis–(methylene)) dipicolinic acid (H 4 pypa-peg) were studied using potentiometry, spectroscopy, competitive complexation liquid–liquid extraction, and ab initio molecular dynamics simulations. Two studied reagents are strong multidentate chelators, well-suited for applications seeking radiometal coordination for in-vivo delivery and f-element isolation. The previously reported H 4 octapa forms a compact coordination packet, while H 4 pypa-peg is less sterically constrained due to the presence of central pyridine ring. The solubility of H 4 octapa is limited in a non-complexing high ionic strength perchlorate media. However, the introduction of a polyethylene glycol group in H 4 pypa-peg increased the solubility without influencing its ability to complex the lanthanides and minor actinides in solution.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗