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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Structural Diversity and Magnetic Properties of Hybrid Ruthenium Halide Perovskites and Related Compounds

There has been a great deal of recent interest in extended compounds containing Ru 3+ and Ru 4+ in light of their range of unusual physical properties. Many of these properties are displayed in compounds with the perovskite and related structures. Here we report an array of structurally diverse hybrid ruthenium halide perovskites and related compounds: MA 2 RuX 6 (X=Cl or Br), MA 2 MRuX 6 (M=Na, K or Ag; X=Cl or Br) and MA 3 Ru 2 X 9 (X=Br) based upon the use of methylammonium (MA=CH 3 NH 3 + ) on the perovskite A site. The compounds MA 2 RuX 6 with Ru 4+ crystallize in the trigonal space group R3¯m and can be described as vacancy-ordered double-perovskites. The ordered compounds MA 2 MRuX 6 with M + and Ru 3+ crystallize in a structure related to BaNiO 3 with alternating MX 6 and RuX 6 face-shared octahedra forming linear chains in the trigonal P3¯m space group. The compound MA 3 Ru 2 Br 9 crystallizes in the orthorhombic Cmcm space group and displays pairs of face-sharing octahedra forming isolated Ru 2 Br 9 moieties with very short Ru–Ru contacts of 2.789 Å. The structural details, including the role of hydrogen bonding and dimensionality, as well as the optical and magnetic properties of these compounds are described. The magnetic behavior of all three classes of compounds is influenced by spin–orbit coupling and their temperature-dependent behavior has been compared with the predictions of the appropriate Kotani models.

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

Conformational Panorama and Chirality Controlled Structure–Energy Relationship in a Chiral Carboxylic Acid Dimer

Chirality recognition in dimers of tetrahydro-2-furoic acid (THFA) was studied in a conformer-specific manner using rotational spectroscopy and theoretical approaches. THFA shows a strong preference for the trans- over the cis-COOH configuration. Two drastically different scenarios are possible for the detectable (THFA) 2 : a kinetically preferred dimer bound by feeble interactions between two trans-THFAs or a thermodynamically favored dimer with a double hydrogen-bonded ring structure between two cis subunits. To identify the conformers responsible for the extremely dense rotational spectra observed, it was essential not only to locate several hundred homo/heterochiral (THFA) 2 minima in ab initio calculations but also to evaluate the energetic connectivities among the minima. The study further reveals an interesting chirality dependent structure-energy ordering relationship. A method for enantiomeric excess (ee) determination of THFA is presented using a recently proposed chiral self-tag approach.

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

The Influence of C(sp 3 )H–Selenium Interactions on the 77 Se NMR Quantification of the π-Accepting Properties of Carbenes

Selenium NMR has become a standard tool for scaling the p-accepting character of carbenes. Herein, we highlight that non-classical hydrogen bonding (NCHB), likely resulting from hyperconjugation, can play a significant role in the carbene–selenium 77 Se NMR chemical shift, thus triggering a non-linear behavior of the Se-Scale.

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

Purification of Propylene and Ethylene by a Robust Metal–Organic Framework Mediated by Host–Guest Interactions

Industrial purification of propylene and ethylene requires cryogenic distillation and selective hydrogenation over palladium catalysts to remove propane, ethane and/or trace amounts of acetylene. Here, we report the excellent separation of equimolar mixtures of propylene/propane and ethylene/ethane, and of a 1/100 mixture of acetylene/ethylene by a highly robust microporous material, MFM-520, under dynamic conditions. In situ synchrotron single crystal X-ray diffraction, inelastic neutron scattering and analysis of adsorption thermodynamic parameters reveal that a series of synergistic host-guest interactions involving hydrogen bonding and π⋯π stacking interactions underpin the cooperative binding of alkenes within the pore. Notably, the optimal pore geometry of the material enables selective accommodation of acetylene. The practical potential of this porous material has been demonstrated by fabricating mixed-matrix membranes comprising MFM-520, Matrimid and PIM-1, and these exhibit not only a high permeability for propylene (≈1984 Barrer), but also a separation factor of 7.8 for an equimolar mixture of propylene/propane at 298 K.

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

Histidine-Mediated Ion Specific Effects Enable Salt Tolerance of a Pore-Forming Marine Antimicrobial Peptide

Antimicrobial peptides (AMPs) preferentially permeate prokaryotic membranes via electrostatic binding and membrane remodeling. Such action is drastically suppressed by high salt due to increased electrostatic screening, thus it is puzzling how marine AMPs can possibly work. We examine as a model system, piscidin-1, a histidine-rich marine AMP, and show that ion-histidine interactions play unanticipated roles in membrane remodeling at high salt: Histidines can simultaneously hydrogen-bond to a phosphate and coordinate with an alkali metal ion to neutralize phosphate charge, thereby facilitating multidentate bonds to lipid headgroups in order to generate saddle-splay curvature, a prerequisite to pore formation. A comparison among Na + , K + , and Cs + indicates that histidine-mediated salt tolerance is ion specific. Here we conclude that histidine plays a unique role in enabling protein/peptide-membrane interactions that occur in marine or other high-salt environment.

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

Proton Traffic Jam: Effect of Nanoconfinement and Acid Concentration on Proton Hopping Mechanism

Abstract The properties of the water network in concentrated HCl acid pools in nanometer‐sized reverse nonionic micelles were probed with TeraHertz absorption, dielectric relaxation spectroscopy, and reactive force field simulations capable of describing proton hopping mechanisms. We identify that only at a critical micelle size of W 0 =9 do solvated proton complexes form in the water pool, accompanied by a change in mechanism from Grotthuss forward shuttling to one that favors local oscillatory hopping. This is due to a preference for H + and Cl − ions to adsorb to the micelle interface, together with an acid concentration effect that causes a “traffic jam” in which the short‐circuiting of the hydrogen‐bonding motif of the hydronium ion decreases the forward hopping rate throughout the water interior even as the micelle size increases. These findings have implications for atmospheric chemistry, biochemical and biophysical environments, and energy materials, as transport of protons vital to these processes can be suppressed due to confinement, aggregation, and/or concentration.

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

A {Ni 12 }-Wheel-Based Metal-Organic Framework for Coordinative Binding of Sulphur Dioxide and Nitrogen Dioxide

Air pollution by SO 2 and NO 2 has caused significant risks on the environment and human health. Understanding the mechanism of active sites within capture materials is of fundamental importance to the development of new clean-up technologies. We report the crystallographic observation of reversible coordinative binding of SO 2 and NO 2 on open Ni II sites in a metal-organic framework (NKU-100) incorporating unprecedented {Ni 12 }-wheels; each wheel exhibits six open Ni II sites on desolvation. Immobilised gas molecules are further stabilised by cooperative host-guest interactions comprised of hydrogen bonds, π∙∙∙π interactions and dipole interactions. At 298 K and 1.0 bar, NKU-100 shows adsorption uptakes of 6.21 and 5.80 mmol g -1 for SO 2 and NO 2 , respectively. Dynamic breakthrough experiments have confirmed the selective retention of SO 2 and NO 2 at low concentrations under dry conditions. This work will inspire the future design of efficient sorbents for the capture of SO 2 and NO 2 .

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

Reshaping the 2‐Pyrone Synthase Active Site for Chemoselective Biosynthesis of Polyketides

Abstract Engineering enzymes with novel reactivity and applying them in metabolic pathways to produce valuable products are quite challenging due to the intrinsic complexity of metabolic networks and the need for high in vivo catalytic efficiency. Triacetic acid lactone (TAL), naturally generated by 2‐pyrone synthase (2PS), is a platform molecule that can be produced via microbial fermentation and further converted into value‐added products. However, these conversions require extra synthetic steps under harsh conditions. We herein report a biocatalytic system for direct generation of TAL derivatives under mild conditions with controlled chemoselectivity by rationally engineering the 2PS active site and then rewiring the biocatalytic pathway in the metabolic network of E. coli to produce high‐value products, such as kavalactone precursors, with yields up to 17 mg/L culture. Computer modeling indicates sterics and hydrogen‐bond interactions play key roles in tuning the selectivity, efficiency and yield.

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

Multi–Step Nucleation of a Crystalline Silicate Framework via a Structurally Precise Prenucleation Cluster

Hierarchical nucleation pathways are ubiquitous in the synthesis of minerals and materials. In the case of zeolites and metal–organic frameworks, pre-organized multi-ion “secondary building units” (SBUs) have been proposed as fundamental building blocks. However, detailing the progress of multi-step reaction mechanisms from monomeric species to stable crystals and defining the structures of the SBUs remains an unmet challenge. Furthermore, combining in situ nuclear magnetic resonance, small-angle X-ray scattering, and atomic force microscopy, we show that crystallization of the framework silicate, cyclosilicate hydrate, occurs through an assembly of cubic octameric Q 3 8 polyanions formed through cross-linking and polymerization of smaller silicate monomers and other oligomers. These Q 3 8 are stabilized by hydrogen bonds with surrounding H 2 O and tetramethylammonium ions (TMA + ). When Q 3 8 levels reach a threshold of ≈32 % of the total silicate species, nucleation occurs. Further growth proceeds through the incorporation of [(TMA) x (Q 3 8 )•n H 2 O] (x–8) clathrate complexes into step edges on the crystals.

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

Facet-Dependent Water Inhibition of Alkanol Dehydration on TiO2 via Distinct Water–Alkanol Complexes

Water is ubiquitous in biomass-derived feeds, yet its molecular impact on oxygen-elimination reactions remains poorly understood, particularly for catalysts exposing different facets. Here, we utilize well-defined TiO2 nanocrystals with dominant (101) and (001) facets to reveal a pronounced facet-dependent effect of water, where inhibition for dehydration of isopropanol (IPA) on the TiO2(001) surface is about four times more severe than TiO2(101). Through a combination of in situ solid state NMR, in situ infrared spectroscopy, kinetics studies, and theoretical calculations, we demonstrate that this disparity arises from the formation of distinct alkanol-water complex intermediates. On TiO2(001), IPA undergoes dissociative adsorption to form an isopropoxide-H2O complex that readily drives the surface into a complex-dominated regime. This pathway increases the activation barrier for C–H cleavage by 40 kJ mol-1 by inducing a disordered transition state. In contrast, TiO2(101) favors molecular IPA adsorption with weak hydrogen bonding to water, resulting in a smaller complex formation constant and a much smaller activation barrier increase (25 kJ mol-1). By quantitatively linking facet-dependent complex coverage to transition-state destabilization, this work moves beyond simple site-blocking models and provides a conceptual framework for designing catalysts that remain active in water-containing environments

Hu, Wenda↗
DOE OSTI2026

A Circular and Tacticity‐Independent Crystalline Mono‐Substituted Nylon‐6 Platform: Unexpected Large Positional Effects on Crystallizability and Performance

Seeking recyclable, more sustainable alternatives to nylon 6 has drawn much attention, but achieving its variants with both crystallinity and enhanced recyclability still remains a challenge. Here, by utilizing bio-derivable mono-substituted racemic lactam monomers, we reveal surprisingly large effects of methyl substitution positions on the nylon-6 backbone on crystallizability, thermomechanical performance, and recyclability of the resulting atactic nylon-6 variants. While γ-methyl substitution gives an amorphous nylon, all other four methyl-substitution positions (α, β, δ, and ε) afford, unexpectedly, crystalline nylons with melting temperatures ranging from 145°C to 200°C and tunable mechanical performance from being stiff and strong (α, ε) to ductile (β, δ). Investigations reveal that the crystallinity of atactic nylons arises independently of stereoregularity, which is driven by the amide backbone with robust hydrogen-bonding interactions and countered by the chain flexibility regulated by the substitution position. These nylons can be chemically recycled back to their parent monomers with high isolated yields up to 92%, enabling a circular, tacticity-independent crystalline nylon platform.

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

Hierarchical assemblies of polypeptoids for rational design of advanced functional nanomaterials

Polypeptoids (poly-N-substituent glycines) are a class of highly tailorable peptidomimetic polymers. Polypeptoids have identical backbones as polypeptides (poly-C-substituent glycines), but sidechains of polypeptoids are appended to backbone nitrogen rather than α-carbon of polypeptides. As a result, peptoid backbone lacks of chirality and hydrogen bond donors. This unique structure gives polypeptoids a combined merit of both high stability as synthetic polymers and biocompatibility as biopolymers. In addition, peptoid sequences can be engineered precisely to assemble specific crystalline patterns such as spheres, fibers, ribbons, tubes, and sheets, which shows promising potentials of polypeptoids for different applications such as antimicrobials, catalysts, drug delivery, and templating inorganic materials. In this review, we summarize recent investigations into hierarchical self-assembly pathways and molecular structures of peptoid crystals that are of interest as templates for fabricating functional materials for potential biomedical, biochemical, and bioengineering applications. Furthermore, this review provides a summary of recent experimental and computational studies of polypeptoid assembly in solution and solid-liquid interfaces, current achievements in the field, and discusses future challenges and opportunities for the rational design of self-assembled polypeptoid nanomaterials.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Intercalated water in aqueous batteries

The unprecedentedly growing demand for energy storage devices in recent years calls for diversified chemistries with unique advantages. When it comes to safety and cost, aqueous battery systems have attracted tremendous attention. Being a universal solvent, water can solvate the cations with rather high dehydration energy due to the hydrogen bonding environment, relatively small size and high polarity. Such properties make solvent co-intercalation, which is seen in a few of the non-aqueous systems, more likely to happen in aqueous batteries. Hydrated cations show drastically different behaviors from naked cations during intercalation/de-intercalation processes and hence enable many reactions that are otherwise difficult to proceed. This review summarizes the roles of co-intercalated water in aqueous batteries from how water molecules coordinate with cations to examples of water-mediated reactions in different types of host materials.

25 ENERGY STORAGE↗
DOE OSTI2023

Organo‐Functionalized Lacunary Double Cubane‐Type Oxometallates: Synthesis, Structure, and Properties of [(M II Cl) 2 (V IV O) 2 {((HOCH 2 CH 2 )(H)N(CH 2 CH 2 O))(HN(CH 2 CH 2 O) 2 )} 2 ] (M=Co, Zn)

Abstract Organofunctionalized tetranuclear clusters [(M II Cl) 2 (V IV O) 2 {((HOCH 2 CH 2 )(H)N(CH 2 CH 2 O))(HN(CH 2 CH 2 O) 2 )} 2 ] (1, M=Co,2: M=Zn) containing an unprecedented oxometallacyclic {M 2 V 2 Cl 2 N 4 O 8 } (M=Co, Zn) framework have been prepared by solvothermal reactions. The new oxo‐alkoxide compounds were fully characterized by spectroscopic methods, magnetic susceptibility measurement, DFT and ab initio computational methods, and complete single‐crystal X‐ray diffraction structure analysis. The isostructural clusters are formed of edge‐sharing octahedral {VO 5 N} and trigonal bipyramidal {MO 3 NCl} units. Diethanolamine ligates the bimetallic lacunary double cubane core of1and2in an unusual two‐mode fashion, unobserved previously. In the crystalline state, the clusters of1and2are joined by hydrogen bonds to form a three‐dimensional network structure. Magnetic susceptibility data indicate weakly antiferromagnetic interactions between the vanadium centers [J iso (V IV −V IV )=−5.4(1); −3.9(2) cm −1 ], and inequivalent antiferromagnetic interactions between the cobalt and vanadium centers [J iso (V IV −Co II )=−12.6 and −7.5 cm −1 ] contained in1.

Chemistry↗
DOE OSTI2024

Probing Noncovalent Interaction Strengths of Host-Guest Complexes Using Negative Ion Photoelectron Spectroscopy

Noncovalent interactions (NCIs) are crucial for the formation and stability of host-guest complexes, which have wide-ranging implications across various fields, including biology, chemistry, materials science, pharmaceuticals, and environmental science. However, since NCIs are relatively weak and sensitive to bulk perturbation, direct and accurate measurement of their absolute strength has always been a significant challenge. This concept article aims to demonstrate the gas-phase electrospray ionization (ESI)-negative ion photoelectron spectroscopy (NIPES) as a direct and precise technique to measure the absolute interaction strength, probe nature of NCIs, and reveal the electronic structural information for host-guest complexes. Here, our recent studies in investigating various host-guest complexes that involve various types of NCIs such as anion–π, (di)hydrogen bonding, charge-separated ionic interactions, are overviewed. Finally, a summary and outlook are provided for this field.

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

Exploration of Nirmatrelvir Derivatives as Optimized SARS‐CoV‐2 Antivirals

Nirmatrelvir (NMV) is a SARS‐CoV‐2 antiviral component of the approved COVID‐19 therapeutic Paxlovid. It is a reversible covalent inhibitor of SARS‐CoV‐2 main protease (M Pro ) that is effluxed from human cells by P‐glycoprotein (P‐gp). To identify NMV analogs with improved potency and reduced P‐gp efflux, a structure–activity relationship campaign was conducted. Warheads alternative to nitrile for engaging the active site cysteine were tested showing aldehyde and dichloroacetamide with better enzyme inhibition potency. Crystal structure of MPI‐136−M Pro shows its aldehyde warhead forming a thiohemiacetal with active Cys145 of M Pro . Several S4 binders were explored revealing that an O‐to‐S shift at the N ‐terminal amide leads to better enzyme inhibition. By exploring different combinations of S2, S3, and S4 binders, two inhibitors with better enzyme inhibition potency than NMV were found. Crystal structure of MPI‐148, with ( S )‐2‐azaspiro[4,5]decane‐3‐carboxylate as an alternative S2 binder, shows extensive hydrogen‐bond networks for locking the inhibitor in active site, explaining high affinity of NMV analogs. Further characterization of cellular M Pro engagement and antiviral potency against SARS‐CoV‐2 revealed four inhibitors with greater potency than NMV in P‐gp‐expressing cells. Studies with the P‐gp inhibitor CP‐100356 showed that these compounds were less sensitive to P‐gp inhibition than NMV, consistent with reduced P‐gp‐mediated efflux.

Alugubelli, Yugendar R. [Texas A&M Drug Discovery ↗
DOE OSTI2020

Influence of TMAO as co-solvent on the gelation of silica-PNIPAm core-shell nanogels at intermediate volume fractions

We study the structure and dynamics of poly(N-isopropylacrylamide) (PNIPAm) core-shell nanogels dispersed in aqueous trimethylamine N-oxide (TMAO) solutions by means of smallangle X-ray scattering and X-ray photon correlation spectroscopy (XPCS). Upon increasing the temperature above the lower critical solution temperature of PNIPAm at 33°C, a colloidal gel is formed as identified by an increase of I(q) at small q as well as a slowing down of sample dynamics by various orders of magnitude. With increasing TMAO concentration the gelation transition shifts linearly to lower temperatures. Above a TMAO concentration of approximately 0.40 mol/L corresponding to a 1:1 ratio of TMAO and NIPAm groups, collapsed PNIPAm states are found for all temperatures without any gelation transition. This suggests that reduction of PNIPAm-water hydrogen bonds due to the presence of TMAO results in a stabilisation of the collapsed PNIPAm state and suppresses gelation of the nanogel.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗