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Batista, Enrique Ricardo

Publications and source records attributed to Batista, Enrique Ricardo.

12 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Advances in heavy alkaline earth chemistry provide insight into complexation of weakly polarizing Ra 2+ , Ba 2+ , and Sr 2+ cations

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.

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

In-situ Synthesis of PuCl 3 and Corresponding Raman and Density Functional Theory Vibrational Modes

The experimental and calculated Raman spectrum of PuCl 3 has been reported for the first time. PuCl 3 is a primary species found in plutonium metal refinement, specifically in pyrochemical salt processes including multicycle direct oxide reduction, metal chlorination, and electrorefining. As such, Raman signatures of PuCl 3 could serve as potential forensic indicators of material process history. A novel technique for synthesizing PuCl 3 from the in situ chlorination of plutonium metal with HCl was developed to establish these signatures. Cerium metal surrogates were utilized to ensure optimization of the plutonium experiments and to minimize personnel exposure, and all experiments were carried out in a Raman reaction chamber designed for air-tight, high vacuum environments. In situ Raman spectroscopy was employed in conjunction with density functional theory (DFT) to investigate the vibrational modes of PuCl 3 . Associated mixed oxy and hydroxyl phases are also reported. The combined Raman and DFT results have eliminated inconsistencies in Raman mode assignments for the MX 3 family of metal chlorides having P6 3 /m symmetry, and IR modes derived from the DFT calculations are additionally presented. The data observed in this study are of potential interest to nuclear forensic analyses, nuclear sample aging, nuclear energy, plutonium processing, and stockpile stewardship.

36 MATERIALS SCIENCE↗
DOE OSTI2023

In-situ Synthesis of PuCl 3 and Corresponding Raman and Density Functional Theory Vibrational Modes

The experimental and calculated Raman spectrum of PuCl 3 has been reported for the first time. PuCl 3 is a primary species found in plutonium metal refinement, specifically in pyrochemical salt processes including multicycle direct oxide reduction, metal chlorination, and electrorefining. As such, Raman signatures of PuCl 3 could serve as potential forensic indicators of material process history. A novel technique for synthesizing PuCl 3 from the in-situ chlorination of plutonium metal with HCl was developed to establish these signatures. Cerium metal surrogates were utilized to ensure optimization of the plutonium experiments and to minimize personnel exposure, and all experiments were carried out in a Raman reaction chamber designed for air-tight, high vacuum environments. In-situ Raman spectroscopy was employed in conjunction with Density Functional Theory (DFT) to investigate the vibrational modes of PuCl 3 . Associated mixed oxy and hydroxyl phases are also reported. The combined Raman and DFT results have eliminated inconsistencies in Raman mode assignments for the MX 3 family of metal chlorides having P6 3 /m symmetry, and IR modes derived from the DFT calculations are additionally presented. The data observed in this study is of potential interest to nuclear forensic analyses, nuclear sample aging, nuclear energy, plutonium processing, and stockpile stewardship.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Uranium-Mediated Peroxide Activation and a Precursor toward an Elusive Uranium cis -Dioxo Fleeting Intermediate

The activation of chalcogen–chalcogen bonds using organometallic uranium complexes has been well documented for S–S, Se–Se, and Te–Te bonds. In stark contrast, reports concerning the ability of a uranium complex to activate the O–O bond of an organic peroxide are exceedingly rare. Herein, we describe the peroxide O–O bond cleavage of 9,10-diphenylanthracene-9,10-endoperoxide in nonaqueous media, mediated by a uranium(III) precursor [(( Me,Ad ArO) 3 N)U III (dme)] to generate a stable uranium(V) bis-alkoxide complex, namely, [(( Me,Ad ArO) 3 N)U V (DPAP)]. This reaction proceeds via an isolable, alkoxide-bridged diuranium(IV/IV) species, implying that the oxidative addition occurs in two sequential, single-electron oxidations of the metal center, including rebound of a terminal oxygen radical. Furthermore, this uranium(V) bis-alkoxide can then be reduced with KC 8 to form a uranium(IV) complex, which upon exposure to UV light, in solution, releases 9,10-diphenylanthracene to generate a cyclic uranyl trimer through formal two-electron photooxidation. Analysis of the mechanism of this photochemical oxidation via density functional theory (DFT) calculations indicates that the formation of this uranyl trimer occurs through a fleeting uranium cis-dioxo intermediate. At room temperature, this cis-configured dioxo species rapidly isomerizes to a more stable trans configuration through the release of one of the alkoxide ligands from the complex, which then goes on to form the isolated uranyl trimer complex.

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

Influencing Bonding Interactions of the Neptunyl (V, VI) Cations with Electron-donating and -withdrawing Groups

Neptunium makes up the largest percentage of minor actinides found in spent nuclear fuel, yet separations of this element have proven difficult due to its rich redox chemistry. Developing new reprocessing techniques should rely on understanding how to control the Np oxidation state and its interactions with different ligands. Designing new ligands for separations requires understanding how to properly tune a system toward a desired trait through functionalization. Emerging technologies for minor actinide separations focus on ligands containing carboxylate or pyridine functional groups, which are desirable due to their high degree of functionalization. So we use DFT calculations to study the interactions of carboxylate and polypyridine ligands with the neptunyl cation [Np(V/VI)O2] +/2+ . A systematic study is performed by varying the electronic properties of the carboxylate and polypyridine ligands through the inclusion of different electron-withdrawing and electron-donating R groups. We focus on how these groups can affect geometric properties, electronic structure, and bonding characterization as a function of the metal oxidation state and ligand character and discuss how these factors can play a role in neptunium ligand design principles.

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

Near-Threshold Photoemission from Graphene-Coated Cu(110)

In this article, the brightness of electron beams emitted from photocathode sources plays a critical role in determining the performance of x-ray free-electron lasers and ultrafast electron-diffraction applications. In order to achieve the maximum brightness, the electrons need to be emitted from a photocathode with the lowest-possible mean transverse energy (MTE). Recent investigations have shown that capping a Cu(110) photocathode with a monolayer of graphene can protect the quantum efficiency (QE) from long-term exposure to varying vacuum conditions. However, there have been no studies that investigate the effects that a monolayer of graphene has on the MTE. Here, we report on measurements of a graphene-coated Cu(110) single crystal near the photoemission threshold for room and liquid-nitrogen temperatures. At room temperature, a minimum MTE of 25 meV is measured at 295 nm. At liquid-nitrogen temperatures, a minimum MTE of 9 meV is measured at the photoemission threshold of 290 nm.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Hydrazine Energy Storage: Displacing N 2 H 4 from the Metal Coordination Sphere

Hydrogen carriers, such as hydrazine (N 2 H 4 ), may facilitate long duration energy storage, a vital component for resilient grids by enabling more renewable energy generation. Lanthanide coordination chemistry with N 2 H 4 as well as efforts to displace N 2 H 4 from the metal coordination sphere to develop an efficient catalytic production cycle were detailed. Modeling the equilibrium of different ligand coordination, it was predicted that strong sigma donor molecules would be required to displace N 2 H 4 . Monitoring competition experiments with nuclear magnetic resonance confirmed that trimethyl phosphine oxide, dimethylformamide, and dimethyl sulfoxide displaced N 2 H 4 in large or small lanthanide complexes.

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

Screening of metal complexes and organic solvents using the COSMOSAC-LANL model to enhance the energy density in a non-aqueous redox flow cell: an insight into the solubility

In this paper, we have proposed a first-principles methodology to screen transition metal complexes against a particular organic solvent and organic solvents against a particular transition metal complex based on their solubility information without the knowledge of heat of fusion and melting temperature. The energy density of a non-aqueous redox flow cell directly depends on the solubility of the redox active species in the non-aqueous medium. Here, we have used the “COSMOSAC-LANL” activity coefficient model which is based on first-principles COSMO calculations where the microscopic information is passed to the macroscopic world via a dielectric continuum solvation model, followed by a post-statistical thermodynamic treatment of the self-consistent properties of the solute particle to calculate the solubility. To model the activity coefficient at infinite dilution for the binary mixtures, a 3-suffix Margules (3sM) function is introduced for the quantitative estimation of the asymmetric interactions and, for the combinatorial term, the Staverman–Guggenheim (SG) form is used. The new activity coefficient model is separately called the “LANL” activity coefficient model. The metal complex and the organic solvent have been treated as a simple binary mixture. The present model has been applied to a set of 14 different organic solvents and 16 different transition metal complexes. Using the new LANL activity coefficient model in combination with the ADF-COSMOSAC-2013 model, we have shown how one can improve the solubility of a transition metal complex in an organic solvent. We applied our model to screen 84 binary mixtures to predict the compatible pair of redox active species and organic solvent to increase the energy density. The solvation mechanism of the transition metal complexes in the organic solvents was obtained using the new model. The results have been compared with the experimental and theoretical results where they are available.

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

Hyperspectral X-ray Imaging: Progress Towards Chemical Analysis in the SEM

The Hyperspectral X-ray Imaging (HXI) project will enable non-destructive chemical-state determination of nano-scale samples in the electron microscope for nuclear safeguards applications. To efficiently measure chemical state through electron-excited X-ray emission requires a combination of wide spectral bandwidth, high resolution, and high count rate capability. We are building a next-generation X-ray detector based on an array of transition edge sensors (TESs) to make these measurements possible and routine in the scanning electron microscope (SEM). Leveraging the large pixel densities afforded by microwave multiplexing readout and continuous, uninterrupted operation of a cryogen-free dilution refrigerator, this instrument will have efficiency to allow chemical species identification of nano-scale samples in hours instead of days to weeks. We describe prototype pixel designs for this HXI instrument, comprising three pixel types that will make up the hybrid TES array. Engineering design of the integrated HXI cryostat and SEM system is in progress, with full detector commissioning expected in Spring 2021 followed closely by full-scale integration with the SEM. Furthermore, we also report on the commissioning of a complementary TES-based X-ray emission spectroscopy platform for bulk samples to build a spectral library for HXI sample identification.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Structural and Spectroscopic Comparison of Soft-Se vs. Hard-O Donor Bonding in Trivalent Americium/Neodymium Molecules

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. In this work, 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.

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

Iron-iminopyridine complexes as charge carriers for non-aqueous redox flow battery applications

Non-aqueous redox flow batteries (RFBs) have been gaining increased attention in the energy storage arena. Some of their attractive features include the promise for high energy densities, wider voltage windows compared to aqueous systems, as well as wider operating temperature ranges. One of the major challenges in the development of these systems is the lack of electroactive materials that can undergo reversible redox events within the larger potential window of organic solvents. In this paper, we present the design, synthesis, and measurement of electrochemical properties of some iron-based imine- and iminopyridine complexes as promising candidates for RFB applications. Synthesized complexes afforded three reversible redox couples over a ~3 V range. The redox events were also computationally explored and are in good agreement with experimental data. Theoretical calculations show that the redox event at the positive potential can be characterized as metal-centered event corresponding to Fe 3+ → Fe 2+ reduction, while the two redox events at negative potentials are associated with the consecutive reductions of iminopyridine or diimine moieties. This work has led to the identification of a promising anolyte material, [tris(imino)pyridine)Fe][OTf] 2 (1), which is soluble in acetonitrile and is synthesized in two simple steps. This species shows outstanding performance when cycled between 1.0 V and 2.35 V, with 93% coulombic efficiency, 84% energy efficiency, and a capacity decay rate of 0.61% per cycle at 5 mA cm –2 . Further modifications to this kind of charge carrier may lead to the development of high energy density materials for grid scale energy storage applications.

25 ENERGY STORAGE↗