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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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13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Ring Size Effects on the Structures of Sandwich Compounds with a Stoichiometry of C 12 H 12 M (M = Ti–Ni)

Ring size effects on geometries and electronic structures were investigated for the (C n H n )M(C m H m ) (n = 4, 5, or 6; m = 8, 7, or 6; m + n = 12; M = Ti–Ni) systems using density functional theory. The lowest-energy C 12 H 12 M structures for the early transition metals titanium, vanadium, and chromium are the experimentally known singlet (η 5 -C 5 H 5 )Ti(η 7 -C 7 H 7 ), doublet (η 5 -C 5 H 5 )V(η 7 -C 7 H 7 ), and singlet (η 6 -C 6 H 6 ) 2 Cr, respectively. The likewise experimentally known singlet (η 6 -C 6 H 6 ) 2 Ti, doublet (η 6 -C 6 H 6 ) 2 V, and singlet (η 5 -C 5 H 5 )Cr(η 7 -C 7 H 7 ) are the secondlowest- energy structures with only a small energy difference between the two vanadium structures. For the later transition metals, dibenzenemetal complexes are the lowest-energy C 12 H 12 M species with two fully bonded hexahapto benzene rings in the lowest-energy manganese and iron derivatives and one hexahapto and one dihapto benzene ring in the lowest-energy cobalt and nickel derivatives. The lowest-energy (C 5 H 5 )M(C 7 H 7 ) structures for the later transition metals iron, cobalt, and nickel have partially bonded nonplanar C 7 H 7 rings with one or two uncomplexed C=C bonds. The (C 4 H 4 )M(C 8 H 8 ) (M = Ti–Ni) structures with the metal sandwiched between four- and eight-membered rings were found to be much higher in energy than their (C 5 H 5 )M(C 7 H 7 ) and (C 6 H 6 ) 2 M isomers.

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

Doubly Stereogenic Sandwich Frameworks: Diastereomeric Metallobiscorroles

A number of Group 6 metallobiscorrole sandwich compounds with square-antiprismatic coordination were separated into diastereomers by means of careful preparative thin-layer chromatography. The diastereomers differ with respect to the relative orientation of the corrole macrocycles, which are rotated approximately ± 45° or ± 135° relative to each other. The most clear-cut results were obtained for two tungsten corroles, W[TBCF 3 PC] 2 {TBCF 3 PC = meso-tris[3,5-bis(trifluoromethyl)phenyl]corrolato} and W[TDOMePC] 2 [TDOMePC = meso-tris(3,5-dimethoxyphenyl)corrolato], for which single-crystal X-ray structures were obtained for the 135° diastereomer; the existence of the 45° diastereomer was inferred by elimination and with support from DFT calculations. For Mo[TBCF 3 PC] 2 and W[TBCF 3 PC] 2 , both diastereomers were also fully characterized spectroscopically and their 1 H NMR spectra were essentially fully assigned. The fact that each diastereomer is chiral and exists as two enantiomers (which was previously demonstrated for the 135° form of a tungsten biscorrole) establishes the doubly stereogenic nature of the metallobiscorrole framework – to our knowledge, the first such demonstration for a sandwich compound.

Aromatic compounds↗
DOE OSTI2026

A Bis(arenesulfonyl) Peroxide, an Ambient-Stable Oxidant, Is a Strong p-Dopant for Organic Semiconductors

Strong p-dopants are required to dope high-ionization energy organic semiconductors for a variety of potential applications, but strong, simple one-electron oxidants are typically sensitive to reduction by atmospheric moisture and thus challenging to store or handle. Here we show that bis(3,5-bis(trifluoromethyl)benzenesulfonyl) peroxide─a dimer formed by two highly oxidizing radicals─can function as a water-stable yet powerful oxidant, cleanly reacting with some organic semiconductors to form two radical cations and two 3,5-bis-(trifluoromethyl)benzenesulfonate anions, although in other cases sulfonylation reactions can also occur. Notably, this peroxide is capable of p-doping the high-ionization energy polymer poly[(9,9-dioctylfluorene-2,7-diyl)- alt -(benzo[2,1,3]thiadiazol-4,7-diyl)] (F8BT) to afford electrical conductivities of up to 0.03 S cm –1 , while its use with electron-rich poly(3,4-dialkoxythiophene-2,5-diyl) derivatives can afford values up to 100 S cm –1 . Quantum-chemical calculations reveal the peroxide oxidant behaves in a fashion mirroring that of relatively oxygen-stable, but highly reducing, n-dopants that have been developed based on dimers of organic radicals or organometallic sandwich compounds.

doping↗
DOE OSTI2025

Synthesis and Characterization of Solvated and Base-Free Cerium(III) Mixed-Sandwich Complexes

A series of solvated complexes: [(C8H8)Ln(C5Me4R)(DME)] Ln = La, R = -Me; (La-2) Ln = Ce, R = -Me, -SiMe3, -H; (Ce-2, Ce-3, Ce-4), [(dbCOT)Ln(C5Me5)(DME)] (Ln-6), (dbCOT2- = dibenzocyclooctadienide; Ln = Ce, La), [(dbCOT)Ce(C5Me4H)(DME)] (Ce-7) and [(hdcCOT)Ce(C5Me5)(DME)] (Ce-8) (hdcCOT2- = hexahydrodicyclopentacyclooctatetraenide) and base-free mixed-sandwich complexes [(C8H8)Ce(C5Me5)] (Ce-9), [(C8H8)Ce(C5Me4H) (Ce-10) and [(hdcCOT)Ce(C5Me5)] (Ce-11) of the early lanthanide metals cerium and lanthanum comprising variable cyclopentadienide (Cp-) and cyclooctatetraenide (COT2-) ligands is described. To evaluate the effect of cyclopentadienide and cyclooctatetraenide ligands on the characteristics of these complexes, their solid-state structural, electrochemical, and photophysical properties were studied and accompanied by theoretical calculations. To further evaluate the effect of ligands on the topology of the complexes and the reducing properties of the complexes, syntheses of several base-free congeners were pursued, which led to isolation of the first base-free monomeric and polymeric Ce(III) mixed-sandwich compounds.

Lanthanides↗
DOE OSTI2026

A Guide to Nonaqueous Electrochemistry of f-Element Complexes

Electrochemistry is a powerful tool for assessing and understanding the redox chemistry of molecular complexes. Cyclic voltammetry enables the f-element community to study molecules in unusually high or low oxidation states, which potentially pose important broad-scope questions of electronic structure. In the pursuit of boundary-pushing compounds, reactive air- and moisture-sensitive species are often encountered, which can be challenging to characterize, especially when they are chemically incompatible with certain solvents, electrolytes, or electrodes or when their potentials lie outside of common electrochemical windows. Nonaqueous solvents and pseudo reference electrodes complicate many of the standard practices in acquiring high-quality and reproducible electrochemical data. This guide presents a detailed discussion of selecting appropriate cell conditions and referencing and addresses metrics for evaluating electrochemical and chemical reversibility. These methodological approaches have been extended to best practices for the electrochemical analysis of radioactive transuranic complexes.

Electrodes↗
DOE OSTI2026

Group 4 Metallocenes Supported on Sulfated Zirconium Oxide Catalyze Benzene C–H Borylation

C−H bond functionalization of arenes with boranes continues to be a challenge in catalysis, with late transition and rare earth metals shown to be catalytically active. In this study, group 4 metallocenes grafted onto acidic sulfated zirconia (SZO) are demonstrated to catalyze arene borylation with pinacolborane (HBpin). Catalysis studies at partial HBpin conversions (59−68%) using Cp 2 M(Me)/SZO (M = Ti, Zr, or Hf; Cp = cyclopentadienyl) catalysts reveal that Zr exhibits greater selectivity and activity than Ti and Hf. At 0.16 mol % of Zr, Cp 2 ZrMe/SZO achieves 332 turnovers at high HBpin conversion (86%), making this catalyst comparably active to previously reported Ir and Rh C−H borylation catalysts. At 160 °C, a maximum chemoselectivity of 82% for PhBpin was observed at 24% HBpin conversion. The superior activity of ionic Cp 2 ZrMe/SZO compared to neutral Cp 2 ZrMe/SiO 2 demonstrates the borylation mechanism relies on the highly electrophilic, coordinatively unsaturated cationic sites stabilized by the weakly coordinating sulfated support. Furthermore, both catalysts significantly outperform their molecular analogues, Cp 2 ZrMe 2 and [Cp 2 ZrMe][B(C 6 F 5 ) 4 ], suggesting that the support enhances catalytic performance by stabilizing the active species.

Aromatic compounds↗
DOE OSTI2025

Large Hyperfine Coupling Arising from Pseudo- 2 S Ground States in a Series of Lutetium(II) Metallocene Complexes

The synthesis of molecules with strong coupling between electronic and nuclear spins represents an important challenge in molecular quantum information science. Here, we report the synthesis and characterization of the divalent lutetium metallocene complexes Lu(Cp Me 5 )(Cp iPr 5 ) (Cp Me 5 = pentamethylcyclopentadienyl; Cp iPr 5 = pentaisopropylcyclopentadienyl), Lu(Cp iPr 4 Et ) 2 (Cp iPr 4 Et = ethyltetraisopropylcyclopentadienyl), and Lu(Cp iPr 4 ) 2 (Cp iPr 4 = tetraisopropylcyclopentadienyl). The molecular structures of these complexes, as determined through singlecrystal X-ray diffraction, feature a common bent sandwich geometry, with average Cp–Lu–Cp angles ranging from 159.9° to 152.6°. Analysis of continuous-wave electron paramagnetic resonance (EPR) spectra for the complexes reveals nearly isotropic g tensors with only a slight deviation from that of a free electron. Moreover, an extremely large splitting of the eight-line spectra indicates the presence of strong hyperfine coupling, and simulations provide isotropic hyperfine coupling constants of A iso = 4.38, 4.30, and 4.17 GHz across the series, where the value of A iso is found to decrease as the Cp–Lu–Cp angle becomes more acute. Notably, these values are the largest yet observed for any lanthanide complex. Moreover, EPR and computational analysis show that the large values of A iso stem from large s-orbital character up to 41.2% in the corresponding singly occupied molecular orbitals. To our knowledge, this degree of s-character in a molecular orbital is the largest yet reported for an open-shell isolable complex. These results outline a general strategy toward the isolation of paramagnetic molecules with strong hyperfine coupling and highly isotropic doublet electronic ground states.

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

Tunable Multisite Proton-Coupled Electron Transfer Mediators: Distinct Pathways for Substrate Reduction Versus Competing Hydrogen Evolution

Proton-coupled electron transfer (PCET) reagents have emerged as powerful tools for transferring net H atoms to organic substrates from relatively weak X–H bonds. One advantage of employing PCET reagents is the tunability of the X–H bond strength by independently varying their redox potential and/or p K a for selective substrate reductions; however, the rational development of modular catalytic PCET reagents based on these features remains underdeveloped. In this work, we address important mechanistic questions relevant to a dimethylaniline-appended cobaltocene PCET mediator that our lab has previously introduced. Specifically, we examine where protonation occurs within the reactive Co(II, NH) + intermediate of a Brønsted-base modified cobaltocene mediator, whether substrate reduction and hydrogen evolution reaction (HER) proceed by a common or bifurcated mechanistic pathway, and how the redox, acid–base, and structural properties of PCET mediators can dictate their reactivity and selectivity. We show that substrate compatibility can be tuned and, via a model study with N -aryl imine substrates, provide data pointing to a multisite PCET (MS-PCET) pathway. Moreover, we rigorously characterize the site of protonation in the reactive reduced, protonated form of the mediator, and through kinetic analysis establish that the pathway for undesired competing HER is fundamentally different and involves Cp-ring protonation. Our findings point to a high degree of flexibility in the design of reductive PCET mediators.

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

Isolation of a new polyoxometalate complex of plutonium

We report the synthesis, plus structural and spectroscopic characterization, of a plutonium(IV) complex with the polyoxometalate W 5 O 18 6− . The complex was isolated as Cs 8 [Pu(W 5 O 18 ) 2 ]·CsCl·6.5H 2 O, with the tetravalent actinide cation sandwiched between two lacunary polyoxotungstate anions. It represents a rare case of a POM compound with plutonium and also the first Peacock–Weakley type complex of plutonium.

Colliard, Ian [Lawrence Livermore National Laborat↗
DOE OSTI2024

Venturing Past Uranium: Synthesis of a Np(IV) Polyoxomolybdate–Alkoxide Sandwich Complex

The synthesis of a Np(IV) polyoxomolybdate– alkoxide sandwich complex, (TBA) 2 [Np{Mo 5 O 13 (OMe) 4 NO} 2 ] (TBA = tetrabutylammonium), is reported. This compound represents a rare example of a neptunium polyoxometalate cluster isolated outside of water, allowing for characterization of its electrochemical properties in nonaqueous solvents. Complexation of An(IV) cations fine-tunes the redox properties of the cluster, with the observed four reversible reductive events varying slightly both in potential and peak separation depending on the actinide present. The new Np(IV) complex also shows an irreversible event assigned to oxidation of Np(IV) to Np(V). New methodology for facile 17 O enrichment of (TBA) 2 [Mo 5 O 13 (OMe) 4 NO][Na(MeOH)] is presented, which provides a simple pathway to 17 O enriched analogues of the sandwich complexes discussed (Zr(IV), Hf(IV), Th(IV), U(IV), U(V), Np(IV)). 17 O NMR spectroscopy subsequently provides insights into both the nature of metal–oxygen bonding, as well as the influence of unpaired f-electrons on the local environment of the oxygen nuclei.

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

Alkali-Metal Interlocking of 2D V 4 O 10 Sheets Defines Discretized Interlayer Shear Relationships

Low-dimensional materials manifest structural anisotropy, quantum confinement, and tightly bound excitonic states, which make them attractive building blocks that can be assembled within three-dimensional laterally stitched heterostructures, stacked van der Waals solids, and complex moiré superlattices. Ion intercalation in the galleries between layered materials provides a means of modifying interlayer separation and coupling, but it is also known to drive the shearing of the layers. In this article, we explore the distinct ligand coordination environments afforded by vanadyl oxygens of singular [V 4 O 10 ] sheets and examine how the size, polarizability, and stoichiometry of Group I cations sandwiched between such layers determine the interlocking of the sheets in stacked structures. Based on the topochemical insertion of alkali-metal ions into the layered λ-V 2 O 5 , we identify seven types of guest ion coordination sites discretized into four distinct regimes of interlayer shear in units of half octahedral widths. The coordination preferences of intercalated cations govern how they interlock 2D [V 4 O 10 ] sheets and engender specific shear conformations. We present evidence that static and dynamic disorder in guest ion arrangement modulate the magnetic structure of the intercalated compounds based on electrostatic polarization, localization of charge and spin density, and lattice distortion. The results illustrate the use of topochemical ion insertion to modulate stacking relationships and magnetic transition characteristics.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Van der Waals Sandwich Structures for Surface-Enhanced Raman Scattering

Surface-enhanced Raman scattering (SERS) intensity of two-dimensional (2D) materials critically depends on the resonant conditions and factors such as the substrate interferences and molecule adsorption fluctuations, making comprehensive investigation, understanding, and optimization of 2D materials-assisted SERS challenging. Here, in this work, the wavelength-dependent SERS of van der Waals structures of 2D materials is systematically investigated, focusing on the intrinsic frequency-dependent Raman tensors by first-principles method while ruling out other extrinsic factors in experiments. Distinct enhancement profiles are found for different 2D materials, among which MoS2 and graphene exhibit remarkably strong and broadband enhancement effects. For stacked multilayers and heterostructures of 2D materials, the calculated SERS addresses the significance of the first contact monolayer effect. Based on the above theory, the van der Waals sandwich structures are proposed and investigated as the SERS substrates, verifying a further significantly enhanced SERS performance. This resonant first-principles study demonstrates a comprehensive and analytical way to explore and promote the SERS of van der Waals structures.

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

Uncooled GeSn MWIR Photodetectors Using Fully Relaxed Thin Triple‐Step Buffer

GeSn photodetectors monolithically grown on Ge virtual substrates demonstrate mid-wave infrared (MWIR) detection at room temperature. The lattice mismatch between GeSn and Ge causes dislocations and compressive strain, creating leakage pathways and unwanted indirect band transitions. Designed thin Ge 0.91 Sn 0.09 triple-step buffer layers of ≈175 nm total thickness reduce dislocations and enable full relaxation, showing 100% lattice relaxation and smooth surface roughness of 0.83 nm with shorter auto-correlation length in surface morphology compared to single-step buffers. Ge 1-x Sn x photodetectors (x = 0.09, 0.12, and 0.15) on triple-step buffers with n-i-p configurations achieve lattice strain relaxations of 99%, 88%, and 80%, respectively. Ge 0.91 Sn 0.09 and Ge 0.88 Sn 0.12 show gradual variation in auto-correlation amplitude, while Ge 0.85 Sn 0.15 shows an increase due to lattice mismatch. Shockley–Read–Hall recombination current dominates at low reverse bias due to mismatch-induced dislocations, while band-to-band tunneling current dominates at higher reverse bias due to narrowing bandgap under strong electric fields. Here, the photodetectors show extended spectral response with increasing Sn composition of i-GeSn active layer sandwiched by barriers. Ge 0.88 Sn 0.12 and Ge 0.85 Sn 0.15 exhibit extended wavelength cut-offs of 3.12 and 3.27 µm at room temperature, demonstrating significant potential for silicon-based MWIR applications.

GeSn↗