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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Li4TiMn8O18 by Materials Project

Li4TiMn8O18 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are eight inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Li–O bond distances ranging from 2.14–2.38 Å. In the second Li1+ site, Li1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Li–O bond distances ranging from 2.20–2.59 Å. In the third Li1+ site, Li1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Li–O bond distances ranging from 2.20–2.59 Å. In the fourth Li1+ site, Li1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Li–O bond distances ranging from 2.13–2.38 Å. In the fifth Li1+ site, Li1+ is bonded in a distorted square co-planar geometry to four O2- atoms. There are two shorter (2.12 Å) and two longer (2.18 Å) Li–O bond lengths. In the sixth Li1+ site, Li1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Li–O bond distances ranging from 2.24–2.65 Å. In the seventh Li1+ site, Li1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Li–O bond distances ranging from 2.24–2.64 Å. In the eighth Li1+ site, Li1+ is bonded in a distorted square co-planar geometry to four O2- atoms. There are two shorter (2.12 Å) and two longer (2.18 Å) Li–O bond lengths. There are two inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two equivalent MnO6 octahedra, edges with two equivalent TiO6 octahedra, and edges with two equivalent MnO6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are a spread of Ti–O bond distances ranging from 1.89–2.09 Å. In the second Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two equivalent MnO6 octahedra, edges with two equivalent TiO6 octahedra, and edges with two equivalent MnO6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are a spread of Ti–O bond distances ranging from 1.90–2.09 Å. There are sixteen inequivalent Mn+3.50+ sites. In the first Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form edge-sharing MnO6 octahedra. There are a spread of Mn–O bond distances ranging from 1.92–2.05 Å. In the second Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are a spread of Mn–O bond distances ranging from 1.95–2.05 Å. In the third Mn+3.50+ site, Mn+3.50+ is bonded to five O2- atoms to form MnO5 square pyramids that share corners with six MnO6 octahedra and edges with two equivalent MnO5 square pyramids. The corner-sharing octahedra tilt angles range from 52–65°. There are a spread of Mn–O bond distances ranging from 1.97–2.08 Å. In the fourth Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with two equivalent MnO6 octahedra, corners with two equivalent MnO5 square pyramids, and edges with four MnO6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are a spread of Mn–O bond distances ranging from 1.93–1.97 Å. In the fifth Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with four MnO5 square pyramids, edges with two equivalent TiO6 octahedra, and edges with two equivalent MnO6 octahedra. There is two shorter (1.92 Å) and four longer (1.95 Å) Mn–O bond length. In the sixth Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with four MnO5 square pyramids, edges with two equivalent TiO6 octahedra, and edges with two equivalent MnO6 octahedra. There are a spread of Mn–O bond distances ranging from 1.92–1.96 Å. In the seventh Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with two equivalent MnO6 octahedra, corners with two equivalent MnO5 square pyramids, and edges with four MnO6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are a spread of Mn–O bond distances ranging from 1.94–1.97 Å. In the eighth Mn+3.50+ site, Mn+3.50+ is bonded to five O2- atoms to form MnO5 square pyramids that share corners with six MnO6 octahedra and edges with two equivalent MnO5 square pyramids. The corner-sharing octahedra tilt angles range from 52–65°. There are a spread of Mn–O bond distances ranging from 1.96–2.08 Å. In the ninth Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are a spread of Mn–O bond distances ranging from 1.95–2.06 Å. In the tenth Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form edge-sharing MnO6 octahedra. There are a spread of Mn–O bond distances ranging from 1.92–2.05 Å. In the eleventh Mn+3.50+ site, Mn+3.50+ is bonded to five O2- atoms to form MnO5 square pyramids that share corners with six MnO6 octahedra and edges with two equivalent MnO5 square pyramids. The corner-sharing octahedra tilt angles range from 51–65°. There are four shorter (1.97 Å) and one longer (2.11 Å) Mn–O bond lengths. In the twelfth Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with two equivalent TiO6 octahedra, corners with two equivalent MnO5 square pyramids, and edges with four MnO6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are a spread of Mn–O bond distances ranging from 1.95–2.05 Å. In the thirteenth Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with four MnO5 square pyramids and edges with four MnO6 octahedra. There are a spread of Mn–O bond distances ranging from 1.93–1.97 Å. In the fourteenth Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with four MnO5 square pyramids and edges with four MnO6 octahedra. There are a spread of Mn–O bond distances ranging from 1.93–1.97 Å. In the fifteenth Mn+3.50+ site, Mn+3.50+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with two equivalent TiO6 octahedra, corners with two equivalent MnO5 square pyramids, and edges with four MnO6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are a spread of Mn–O bond distances ranging from 1.95–2.02 Å. In the sixteenth Mn+3.50+ site, Mn+3.50+ is bonded to five O2- atoms to form MnO5 square pyramids that share corners with six MnO6 octahedra and edges with two equivalent MnO5 square pyramids. The corner-sharing octahedra tilt angles range from 51–65°. There are four shorter (1.97 Å) and one longer (2.11 Å) Mn–O bond lengths. There are thirty-six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Mn+3.50+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to three Mn+3.50+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Li1+ and two equivalent Ti4+ atoms. In the fourth O2- site, O2- is bonded to two equivalent Li1+ and three Mn+3.50+ atoms to form distorted OLi2Mn3 trigonal bipyramids that share corners with six OLiMn3 trigonal pyramids and edges with two equivalent OLi2Mn3 trigonal bipyramids. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Li1+ and three Mn+3.50+ atoms. In the sixth O2- site, O2- is bonded to one Li1+ and three Mn+3.50+ atoms to form distorted OLiMn3 trigonal pyramids that share corners with four OLi2Mn3 trigonal bipyramids and corners with two equivalent OLiMn3 trigonal pyramids. In the seventh O2- site, O2- is bonded to two equivalent Li1+ and three Mn+3.50+ atoms to form OLi2Mn3 square pyramids that share corners with two equivalent OLi2Mn3 trigonal bipyramids, edges with two equivalent OLi2Mn3 square pyramids, an edgeedge with one OLi2Mn3 trigonal bipyramid, and edges with two equivalent OLiMn3 trigonal pyramids. In the eighth O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Li1+ and three Mn+3.50+ atoms. In the ninth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Ti4+ and two equivalent Mn+3.50+ atoms. In the tenth O2- site, O2- is bonded to one Li1+ and three Mn+3.50+ atoms to form OLiMn3 trigonal pyramids that share corners with two equivalent OLi2Mn3 trigonal bipyramids, corners with two equivalent OLiMn3 trigonal pyramids, and edges with two equivalent OLi2Mn3 square pyramids. In the eleventh O2- site, O2- is bonded to one Li1+ and three Mn+3.50+ atoms to form OLiMn3 trigonal pyramids that share corners with two equivalent OLi2Mn3 trigonal bipyramids, corners with two equivalent OLiMn3 trigonal pyramids, and edges with two equivalent OLi2Mn3 square pyramids. In the twelfth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Ti4+ and two equivalent Mn+3.50+ atoms. In the thirteenth O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Li1+ and three Mn+3.50+ atoms. In the fourteenth O2- site, O2- is bonded to two equivalent Li1+ and three Mn+3.50+ atoms to form OLi2Mn3 square pyramids that share corners with two equivalent OLi2Mn3 trigonal bipyramids, edges with two equivalent OLi2Mn3 square pyramids, an edgeedge with one OLi2Mn3 trigonal bipyramid, and edges with two equivalent OLiMn3 trigonal pyramids. In the fifteenth O2- site, O2- is bonded to one Li1+ and three Mn+3.50+ atoms to form distorted OLiMn3 trigonal pyramids that share corners with four OLi2Ti2Mn trigonal bipyramids and corners with two equivalent OLiMn3 trigonal pyramids. In the sixteenth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Li1+ and three Mn+3.50+ atoms. In the seventeenth O2- site, O2- is bonded to two equivalent Li1+ and three Mn+3.50+ atoms to form distorted OLi2Mn3 trigonal bipyramids that share corners with six OLiMn3 trigonal pyramids and edges with two equivalent OLi2Mn3 trigonal bipyramids. In the eighteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Li1+ and two equivalent Ti4+ atoms. In the nineteenth O2- site, O2- is bonded in a 3-coordinate geometry to three Mn+3.50+ atoms. In the twentieth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Mn+3.50+ atoms. In the twenty-first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Li1+ and two equivalent Mn+3.50+ atoms. In the twenty-second O2- site, O2- is bonded to two equivalent Li1+, two equivalent Ti4+, and one Mn+3.50+ atom to form distorted OLi2Ti2Mn trigonal bipyramids that share corners with four OLiMn3 trigonal pyramids and edges with two equivalent OLi2Ti2Mn trigonal bipyramids. In the twenty-third O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Li1+ and three Mn+3.50+ atoms. In the twenty-fourth O2- site, O2- is bonded to one Li1+ and three Mn+3.50+ atoms to form distorted OLiMn3 trigonal pyramids that share corners with four OLi2Mn3 trigonal bipyramids and corners with two equivalent OLiMn3 trigonal pyramids. In the twenty-fifth O2- site, O2- is bonded to two equivalent Li1+ and three Mn+3.50+ atoms to form a mixture of edge and corner-sharing OLi2Mn3 trigonal bipyramids. In the twenty-sixth O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Li1+ and three Mn+3.50+ atoms. In the twenty-seventh O2- site, O2- is bonded in a 3-coordinate geometry to three Mn+3.50+ atoms. In the twenty-eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Ti4+ and two equivalent Mn+3.50+ atoms. In the twenty-ninth O2- site, O2- is bonded in a 3-coordinate geometry to one Ti4+ and two equivalent Mn+3.50+ atoms. In the thirtieth O2- site, O2- is bonded in a 3-coordinate geometry to three Mn+3.50+ atoms. In the thirty-first O2- site, O2- is bonded in a 5-coordinate

36 MATERIALS SCIENCE↗
DOE OSTI2024

Coordination of copper within a crystalline carbon nitride and its catalytic reduction of CO 2

Inherently disordered structures of carbon nitrides have hindered an atomic level tunability and understanding of their catalytic reactivity. Starting from a crystalline carbon nitride, poly(triazine imide) or PTI/LiCl, the coordination of copper cations to its intralayer N-triazine groups was investigated using molten salt reactions. The reaction of PTI/LiCl within CuCl or eutectic KCl/CuCl 2 molten salt mixtures at 280 to 450 °C could be used to yield three partially disordered and ordered structures, wherein the Cu cations are found to coordinate within the intralayer cavities. Local structural differences and the copper content, i.e., whether full or partial occupancy of the intralayer cavity occurs, were found to be dependent on the reaction temperature and Cu-containing salt. Crystallites of Cu-coordinated PTI were also found to electrophoretically deposit from aqueous particle suspensions onto either graphite or FTO electrodes. As a result, electrocatalytic current densities for the reduction of CO 2 and H 2 O reached as high as ∼10 to 50 mA cm −2 , and remained stable for >2 days. Selectivity for the reduction of CO 2 to CO vs. H 2 increases for thinner crystals as well as for when two Cu cations coordinate within the intralayer cavities of PTI. Mechanistic calculations have also revealed the electrocatalytic activity for CO 2 reduction requires a smaller thermodynamic driving force with two neighboring Cu atoms per cavity as compared to a single Cu atom. These results thus establish a useful synthetic pathway to metal-coordination in a crystalline carbon nitride and show great potential for mediating stable CO 2 reduction at sizable current densities.

Chemistry↗
DOE OSTI2020

Using Complementary Methods of Synchrotron Radiation Powder Diffraction and Pair Distribution Function to Refine Crystal Structures with High Quality Parameters—A Review

Determination of the atomic-scale structures of certain fine-grained minerals using single-crystal X-ray diffraction (XRD) has been challenging because they commonly occur as submicron and nanocrystals in the geological environment. Synchrotron powder diffraction and scattering techniques are useful complementary methods for studying this type of minerals. In this review, we discussed three example studies investigated by combined methods of synchrotron radiation XRD and pair distribution function (PDF) techniques: (1) low-temperature cristobalite; (2) kaolinite; and (3) vernadite. Powder XRD is useful to determine the average structure including unit-cell parameters, fractional atomic coordinates, occupancies and isotropic atomic displacement parameters. X-ray/Neutron PDF methods are sensitive to study the local structure with anisotropic atomic displacement parameters (ADP). The results and case studies suggest that the crystal structure and high-quality ADP values can be obtained using the combined methods. The method can be useful to characterize crystals and minerals that are not suitable for single-crystal XRD.

58 GEOSCIENCES↗
DOE OSTI2023

Selective scandium ion capture through coordination templating in a covalent organic framework

The use of coordination complexes within covalent organic frameworks can significantly diversify the structures and properties of this class of materials. In this report we combined coordination chemistry and reticular chemistry by preparing frameworks that consist of a ditopic (p-phenylenediamine) and mixed tritopic moieties-an organic ligand and a scandium coordination complex of similar sizes and geometries, both bearing terminal phenylamine groups. Changing the ratio of organic ligand to scandium complex enabled the preparation of a series of crystalline covalent organic frameworks with tunable levels of scandium incorporation. Removal of scandium from the material with the highest metal content subsequently resulted in a 'metal-imprinted' covalent organic framework that exhibits a high affinity and capacity for Sc 3+ ions in acidic environments and in the presence of competing metal ions. In particular, the selectivity of this framework for Sc 3+ over common impurity ions such as La 3+ and Fe 3+ surpasses that of existing scandium adsorbents.

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

Resolving the Atomic Structure of Sequential Infiltration Synthesis Derived Inorganic Clusters

Sequential infiltration synthesis (SIS) is a route to the precision deposition of inorganic solids in analogy to atomic layer deposition but occurs within (vs upon) a soft material template. SIS has enabled exquisite nanoscale morphological complexity in various oxides through selective nucleation in block copolymers templates. However, the earliest stages of SIS growth remain unresolved, including the atomic structure of nuclei and the evolution of local coordination environments, before and after polymer template removal. We employed In K-edge extended X-ray absorption fine structure and atomic pair distribution function analysis of high-energy X-ray scattering to unravel (1) the structural evolution of InO x H y clusters inside a poly(methyl methacrylate) (PMMA) host matrix and (2) the formation of porous In 2 O 3 solids (obtained after annealing) as a function of SIS cycle number. Early SIS cycles result in InO x H y cluster growth with high aspect ratio, followed by the formation of a three-dimensional network with additional SIS cycles. That the atomic structures of the InO x H y clusters can be modeled as multinuclear clusters with bonding patterns related to those in In 2 O 3 and In(OH) 3 crystal structures suggests that SIS may be an efficient route to 3D arrays of discrete-atom-number clusters. As a result, annealing the mixed inorganic/polymer films in air removes the PMMA template and consolidates the as-grown clusters into cubic In 2 O 3 nanocrystals with structural details that also depend on SIS cycle number.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Pnictogen Bonding at the Core of a Carbene-Stiborane-Gold Complex: Impact on Structure and Reactivity

Our interest in the design of ambiphilic ligands and their coordination to gold has led us to synthesize an indazol-3-ylidene gold chloride complex functionalized at the 4-position of the indazole backbone by a stibine functionality. The antimony center of this new complex cleanly reacts with o-chloranil to afford the corresponding stiborane derivative. Structural analysis indicates that the stiborane coordination environment is best described as a distorted square pyramid whose open face is oriented toward the gold center, allowing for the formation of a long donor–acceptor, or pnictogen, Au → Sb bonding interaction. The presence of this interaction, which has been probed computationally, is also manifested in the enhanced catalytic activity of this complex in the cyclization of N-propargyl-4-fluorobenzamide.

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

Structural and spectroscopic characterization of thorium pyrasal complexes

To explore the coordination chemistry of thorium, the most abundant radioactive element on earth, we examine the synthesis and characterization of two Th (IV)-pyrasal complexes, L1 “pyrasal” ((2,2'-((1E,1'E)-(pyrazine-2,3-diylbis(azaneylylidene))bis(methaneylylidene))diphenol), and L2 “naphthylpyrasal” (1,1'-((1E,1'E)-(pyrazine-2,3-diylbis(azaneylylidene))bis(methaneylylidene))bis(naphthalen-2-ol). These complexes demonstrate little or no fluorescence when compared to similar naphthylsalophen thorium complexes previously published. Each complex was synthesized and characterized by IR, NMR (1H), and mass spectrometry. The photometric properties of the complexes were characterized using UV–Vis and fluorescence spectroscopy and their solid-state molecular structures were established by single-crystal X-ray crystallography. The electron-withdrawing effects of the pyrazine ring creates changes in the thorium coordination environment resulting in a secondary solid-state extended structure that minimizes the pi-pi stacking. Further, this subsequently causes an overall decrease in the intensity of fluorescence demonstrated previously in by naphthylsalophen thorium complexes.

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

Connecting cation site location to alkane dehydrogenation activity in Ni/BEA catalysts

Ni-modified beta zeolite (Ni/BEA) catalysts activate carbon-hydrogen bonds in light alkanes, as demonstrated through isobutane reaction testing. Controlled synthesis of Ni/BEA allows for efficient introduction of ion-exchanged Ni sites at varying Ni loadings (0.43% - 1.8%). These catalysts exhibit site time yields (STY) for H2 production that increase with increasing Ni loading. A detailed analysis of secondary reactions and carbon deposition based on the relative molar flowrates of product C and H indicates that the observed increase in H2 STY with increasing Ni loading is likely attributed to both increasing alkane activation activity and increasing formation of hydrogen-deficient aromatic products retained within the catalyst pores. In situ diffuse-reflectance UV-visible-NIR absorbance and X-ray absorption spectroscopies indicate isolated, 4-coordinate Ni(2+) species for all loadings. Quantum mechanics/molecular mechanics modeling identifies two distinct Ni(2+) sites consistent with the structural characterization, but with differing relative stabilities due to their coordination environment. Computed reaction energetics for isobutane dehydrogenation demonstrate that the more stable Ni(2+) species at a six-membered 4Si-2Al ring, Ni-6MR, is less active for isobutane dehydrogenation than the less stable Ni(2+) at the five-membered 3Si-2Al ring, Ni-5MR. The differing local structure of the isolated cationic Ni sites in Ni/BEA offers a possible rationalization for the increased H2 STY observed at greater Ni loadings.

catalysts↗
DOE OSTI2024

Quantifying the Correlation between Coordination Chemistry, Interfacial Formation, and Electrochemical Performances for Mg Battery Electrolytes

Here, the rise of magnesium batteries as promising post-Li-ion energy storage technologies has sparked considerable attention toward understanding the fundamental aspects of coordination chemistry concerning Mg cations in multivalent electrolytes. This exploration includes investigating how coordination influences crucial electrolyte properties like solubility, electroreduction stability, and the formation of the interphase, all of which are pivotal for practical battery applications. Despite recent progress in developing a few functional electrolytes, a comprehensive understanding of the solvation structure that can facilitate efficient Mg deposition performance and the formulation of general design rules based on the solvation structure is still lacking. In our study, we endeavor to establish a connection between solvent and anion interactions with Mg 2+ , interface formation, and cycling performance through a series of organic ether solvents (tetrahydrofuran, glyme, diglyme, and triglyme) and amine solvents (dimethylamine, 3-methoxypropylamine, and dimethoxyethylamine). Our findings reveal a distinct coordination trend for solvent/Mg 2+ and (Mg-TFSI):solvent across various solvents, which dictates the extent of ion pairing for TFSI salts with increasing solvent molecule size and denticity. The solvated species in the bulk electrolyte across different solvents lead to diverse interfacial chemistries with varying decomposition components. We also explore the cycling efficiency as well as Mg deposition overpotentials for different solvents. A correlation analysis was conducted to assess the interplay between the structure and performance. Lastly, we apply the insights gained from these results to tailor the relative anion/Mg 2+ coordination structures using cosolvent systems, aiming for improved cell performance.

25 ENERGY STORAGE↗
DOE OSTI2022

Universally Accessible Structural Data on Macromolecular Conformation, Assembly, and Dynamics by Small Angle X-Ray Scattering for DNA Repair Insights.

Structures provide a critical breakthrough step for biological analyses, and small angle X-ray scattering (SAXS) is a powerful structural technique to study dynamic DNA repair proteins. As toxic and mutagenic repair intermediates need to be prevented from inadvertently harming the cell, DNA repair proteins often chaperone these intermediates through dynamic conformations, coordinated assemblies, and allosteric regulation. By measuring structural conformations in solution for both proteins, DNA, RNA, and their complexes, SAXS provides insight into initial DNA damage recognition, mechanisms for validation of their substrate, and pathway regulation. Here, we describe exemplary SAXS analyses of a DNA damage response protein spanning from what can be derived directly from the data to obtaining super resolution through the use of SAXS selection of atomic models. We outline strategies and tactics for practical SAXS data collection and analysis. Making these structural experiments in reach of any basic and clinical researchers who have protein, SAXS data can readily be collected at government-funded synchrotrons, typically at no cost for academic researchers. In addition to discussing how SAXS complements and enhances cryo-electron microscopy, X-ray crystallography, NMR, and computational modeling, we furthermore discuss taking advantage of recent advances in protein structure prediction in combination with SAXS analysis.

Chinnam, Naga Babu↗
DOE OSTI2020

Nearly Identical but Not Isotypic: Influence of Lanthanide Contraction on Cs 2 NaLn(PS 4 ) 2 (Ln = La–Nd, Sm, and Gd–Ho)

The effect of the lanthanide contraction often results in topological and symmetry changes in compounds with the same compositions as a function of lanthanide cation size. Here we report on the first example of a lanthanide thiophosphate exhibiting a change in the lanthanide cation environment without any topological or symmetry change. A series of new lanthanide thiophosphates with mixed alkali cations was obtained via a flux crystal growth technique using a CsI flux. The obtained compounds Cs 2 NaLn(PS 4 ) 2 (Ln = La–Nd, Sm, Gd–Ho) were grown as large single crystals (~0.1–1 mm 3 ) and characterized using single crystal X-ray diffraction and magnetic susceptibility measurements. Moving across the series, the structural studies revealed a change in the lanthanide coordination environment dependent upon the identity of the lanthanide. Although all compounds in the Cs 2 NaLn(PS 4 ) 2 series crystallize in the same space group and have the same Wyckoff positions of the atoms, a slight size change between Sm 3+ and Gd 3+ causes a subtle change in coordination number from 9 (for Ln = La–Sm) to 8 (for Ln = Gd–Ho), resulting in two distinct but virtually identical structure types. Ab initio calculations were performed, and the observed experimental trend was corroborated computationally. Finally, magnetic measurements performed on the Cs 2 NaLn(PS 4 ) 2 (Ln = Ce, Pr, Nd, Gd, and Tb) compounds revealed paramagnetic behavior.

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

Epoxide Alcoholysis over M-BEA Zeolites: Effects of Alcohol Chain Length on Rates and Regioselectivities

The structures of nucleophilic reactants affect their coordination behavior among solvent molecules and kinetics of reactions with surface intermediates within the confines of fluidfilled pores of zeolites and other microporous materials. Consequently, rates and regioselectivities of diverse chemistries may depend sensitively on nucleophile identity in manners not observed for classic fluid phase reactions. Here, we examine the impact of varying the primary alcohol (ROH) chain length on the kinetics of 1,2-epoxybutane (C 4 H 8 O) ring-opening within Brønsted (Al-BEA) and Lewis acid (Zr-BEA) zeolites. Turnover rates increase by factors of ∼6 (Al-BEA) and 4-fold (Zr-BEA) between methanol and 1-hexanol, yet the reaction mechanisms remain comparable. Despite modest rate differences, apparent activation enthalpies calculated from rates and activities of solvated reactants decrease linearly by 12 (Al-BEA) to 33 kJ mol −1 (Zr- BEA) with increased proton affinity, which suggests bond formation energies for the nucleophile strongly influence rate increases. The molecular interpretation of these trends demonstrates, however, that the solvation of ring-opening transition states by zeolite pore structures and solvent molecules also governs rates. The impact of local solvating interactions appears most directly as changes in regioselectivities, which tend to enhance terminal alcohol formation with increasing ROH chain length. Regioselectivities largely do not vary with differences in fluid composition for a given ROH. The addition of H 2 O increases the number of hydrogen bonds among reactive species, and trends in regioselectivities imply that the decreased hydrogen bonding ability of longer chain ROH, and not the nucleophile strength or steric bulk, determines the regioselectivities of the resulting products. This work provides direct experimental evidence that nucleophilicity and hydrogen bonding influence reaction barriers and regioselectivities in zeolitecatalyzed epoxide ring-opening, offering pathways to better control reaction kinetics.

acidic zeolites↗
DOE OSTI2025

Structural complexity in the f -block: small deviations of the complexation of lanthanides by O,Oʹ -diethylmonothiophosphate

Dithiophosphinic acids undergo radiolytic degradation during the extraction of actinides in used nuclear fuel. These will degrade into monothiophosphinic acids and then to phosphinic acids. To elucidate how the complexes that are formed during these radioactive separations change as the ligand degrades, the mixed donor ligand O,O′- diethylmonothiophosphate is chosen as an analog for the monothiophosphinic intermediate. Herein, the monothiophosphate complexes Ln 2 (OPS(OEt) 2 ) 6 (H 2 O) 8 (Ln = La) (La 2 L 6 H 2 O), Ln 2 (OPS(OEt) 2 ) 6 (EtOH) 4 (Ln = La) (La 2 L 6 EtOH), K 2 [Ln(OPS(OEt) 2 ) 5 (H 2 O) 2 ]·H 2 O·CH 2 Cl 2 , (Ln = Ce) (CeL 5 -α), K 2 [Ln(OPS(OEt) 2 ) 5 (H 2 O) 2 ]·H 2 O·CH 2 Cl 2 , (Ln = Pr) (PrL 5 -β), K[Ln(OPS(OEt) 2 ) 4 (H 2 O) 3 ], (Ln = Pr, Sm-Er) (ML 4 ), and K 3 [Ln(OPS(OEt) 2 ) 6 ], (Ln = Dy) (DyL 6 ) were synthesized and characterized using single-crystal X-ray diffraction and optical spectroscopy. Although the lanthanides contract in a nearly linear fashion, the structural changes observed as the f-block is traversed in these compounds are not necessarily a hard line but more so a blend of different structure types possible for each f-element. Furthermore, comparison of the Ln−O bond lengths shows a nearly linear contraction, but the Ln−S bond lengths do not monotonically decrease because of the hard Lewis acidity of the Ln 3+ cations.

37 - INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL C↗
DOE OSTI2022

Synthesis of an Isostructural Series of 12-Coordinate Lanthanide Nitrate Hybrid Double Perovskites with Cubic Symmetry

In efforts to study the periodic chemical properties of the rare earth elements and their structural chemistry, a hybrid double perovskite phase A 2 B'BX 6 with the formula ((CH 3 ) 4 N) 2 KLn(NO 3 ) 6 (Ln = La–Lu, Y ex. Pm) was synthesized that crystallizes in the cubic space group, $Fm$$\bar{3}$$m$. This series was obtained via evaporative crystallization from a mixture of Ln(NO 3 ) 3 , KNO 3 , and (CH 3 ) 4 N·NO 3 in a 1:1:2 ratio from either H 2 O or 4.0 M HNO 3 . In this double perovskite structure, the B site containing the lanthanide ion is coordinated by six bidentate nitrate ligands, with the distal N$=$O oxygen atoms coordinating the potassium on the B' site in an octahedral six-coordinate environment. The two-remaining charge-compensating (CH 3 ) 4 N + cations occupy the interstitial voids in the lattice on the A site. This periodic series was characterized via single-crystal X-ray diffraction, powder X-ray diffraction, IR, and Raman spectroscopy. Emission spectra of the Eu complex indicate a phase transition to trigonal symmetry upon cooling. In conclusion, this series is unique as it represents a rare isostructural series spanning the entirety of the rare earth elements excluding promethium with homoleptic 12-coordinate rare earth metal ions.

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

Enhancing elastic properties of single element amorphous solids through long-range interactions

Elastic properties of amorphous solids remain a topic of intense interest due to their important roles in a wide range of applications. Prior works have focused on short-range, local structural features, such as number density and coordination number, to elucidate the underlying mechanism of elastic moduli in glasses. Here, we report strong correlations among the spatial extension of the interatomic potential, elastic moduli, and the coherence lengths of the medium-range structural order through molecular dynamics simulations for single element glasses. Our findings demonstrate an unconventional design principle to engineer elastic properties by extending the medium-range order and provide insights into the microscopic origin of elastic properties in amorphous solids.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Spin–Flop and Metamagnetic Transition in Monoclinic Eu 4 Bi 6 Se 13

This study explores an investigation of the crystallographic, electronic, and magnetic properties of the europium-based bismuth selenide compound Eu 4 Bi 6 Se 13 , with particular focus on its magnetic anisotropy. This compound adopts a monoclinic crystal structure classified under the P2 1 /m space group (#11). It exhibits distinctive structural features, including substantial Eu–Se coordination numbers (6 and 8), Bi–Se ladders, and linear chains of Eu atoms that propagate along the b-axis. Electronic resistivity assessments indicate that Eu 4 Bi 6 Se 13 exhibits metallic behavior. As the magnetic field is oriented along the b-axis, magnetic characterization reveals uniaxial magnetic anisotropy, with metamagnetic transitions appearing at approximately 12 kOe and a lower field. In the field below 10 kOe, the spin-flop transition is observed with possible domain-induced hysteresis. This behavior supports the identification of metamagnetic features in field-dependent measurements attributable to the europium spins.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗