Search NASA⌕ Search

SEARCH · Search NASA

Results for “F-block chemistry”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Frontiers in divalent $f$-block chemistry

Divalent f-block chemistry has undergone rapid expansion in recent years, driven by advances in the stabilization of low-valent lanthanide and actinide complexes. Although f-elements were historically accessed in the +3 or higher oxidation states, the isolation of +2 species has revealed unusual spectroscopic signatures, distinct bonding motifs, and multiple accessible electronic configurations that influence their chemical and physical properties. These developments have generated opportunities in areas including quantum information science, molecular magnetism, catalysis, and luminescence. Computational chemistry has played a pivotal role in interpreting the electronic structure and reactivity of these systems. However, accurately modeling divalent f-block complexes remains challenging because of strong electronic correlation, multiconfigurational character, and the presence of close-in-energy competing electronic states. As experimental capabilities and theoretical methodologies continue to advance, a comprehensive assessment of divalent chemistry is both timely and needed. In this Review, we integrate experimental and theoretical perspectives to provide a systematic analysis of divalent lanthanide and actinide complexes across the f-block series. We critically assess the role of ligands in determining competing ground-state configurations (f n d 1 vs. f n+1 ) resulting in their distinct spectroscopic, magnetic, and bonding properties. Finally, we discuss emerging strategies for predictive modeling and rational design of low-valent f-block molecular systems, with potential applications ranging from dinitrogen reduction to quantum technologies.

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

Dateset for Zeolite-confined organolanthanide catalysts for C-H borylation of hydrocarbons

This dataset supports a publication, "Trimethylaluminum Activates Zeolite-Confined Lanthanum Borohydrides to Enhance Catalytic C–H Borylation", in the Journal of the American Chemical Society which describes the lanthanum borohydride catalyzed reaction of pinacolborane and aromatic, heteroaromatic and aliphatic hydrocarbons. The chemical affects of AlMe3 treatment on the precatalyst are explored in detail. The dataset includes characterization of the precatalyst using solid-state nuclear magnetic resonance spectroscopy, X-ray adsorption spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and density functional theory.

F-block chemistry↗
DOE OSTI2024

Observation of a promethium complex in solution

Lanthanide rare-earth metals are ubiquitous in modern technologies, but we know little about chemistry of the 61st element, promethium (Pm), a lanthanide that is highly radioactive and inaccessible. Despite its importance, Pm has been conspicuously absent from the experimental studies of lanthanides, impeding our full comprehension of the so-called lanthanide contraction phenomenon: a fundamental aspect of the periodic table that is quoted in general chemistry textbooks. Here we demonstrate a stable chelation of the 147 Pm radionuclide (half-life of 2.62 years) in aqueous solution by the newly synthesized organic diglycolamide ligand. The resulting homoleptic Pm III complex is studied using synchrotron X-ray absorption spectroscopy and quantum chemical calculations to establish the coordination structure and a bond distance of promethium. These fundamental insights allow a complete structural investigation of a full set of isostructural lanthanide complexes, ultimately capturing the lanthanide contraction in solution solely on the basis of experimental observations. Our results show accelerated shortening of bonds at the beginning of the lanthanide series, which can be correlated to the separation trends shown by diglycolamides. The characterization of the radioactive Pm III complex in an aqueous environment deepens our understanding of intra-lanthanide behaviour and the chemistry and separation of the f-block elements.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Molecular Design of Al(II) Intermediates for Small Molecule Activation

Promoting societally important small molecule activation processes with earth-abundant metals is foundational for a sustainable chemistry future. In this context, mapping new reaction pathways that would enable abundant main-group elements to mimic the behaviors of d- and f-block elements is facilitated by exploring unusual oxidation states. The most abundant metal on earth, aluminum, has been well studied in the Lewis acidic +III and Lewis basic +I oxidation states but rarely in the potentially biphilic +II oxidation state until recently, when a renaissance of Al(II) chemistry emerged from a range of research groups. In this Perspective, we review the chemistry of mononuclear Al radicals, including both Al-centered radicals (i.e., Al(II) compounds) and redox non-innocent systems (i.e., formally Al(II) species that are physically Al(III) with ligand-centered radicals), with an emphasis on small molecule reactivity. We also provide a meta-analysis of the Al(II) literature to summarize how different design strategies (e.g., redox non-innocence, strained coordination geometries) have been shown to impart biphilic character to Al radicals and tune their behavior, thus allowing Al radicals to mimic the chemistry of certain d- and f-block metal ions such as Ti(III) and Sm(II). We expect these molecular design concepts to inform future Al(II) studies as the chemistry of this unusual oxidation state of Al continues to grow.

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

Lanthanum-Doped Graphene for Electrocatalytic Reduction of Nitrogen Monoxide

Electrocatalytic conversion of nitrogen oxides is a promising approach to address nitrogen pollution in underground water. Nitrogen oxides, such as nitrate and nitrite, can be reduced to N 2 and NH 3 over an electrocatalyst, with NO as the key intermediate, subsequent reaction of which controls the overall activity and selectivity. Here, we report density functional theory calculations of NO electrocatalytic reduction (NOER) over lanthanum embedded in graphene, through which we show that the localized states in La drive the reaction favorably due to more pronounced molecular adsorption and charge transfer than transition metals such as Co. The free energy profiles are compared between the La-based single-atom catalyst (SAC) and Co-based SAC, for producing N 2 and NH 3 . We find that the La-SAC intensifies the electron transfer to the adsorbed NO, promoting the first protonation step of NO, which is the potential-limiting step on the Co-SAC. Also, an intriguing effect of the water solvent is revealed on the La-SAC. In addition to stabilizing the intermediate species, water molecules that are coordinated with La participate directly in the protonation steps, enhancing the catalyst activity. Furthermore, this study reveals the unique mechanism of NOER over rare-earth-based catalysts, highlighting the potential application of atomically dispersed f-block elements for electrocatalytic reactions.

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

TALSPEAK-based separation of the trivalent actinides from rare earth elements using LN resin

The separation of 241 Am, 244 Cm and 249 Cf from rare earth elements using LN resin and lactate buffer solutions with diethylenetriaminepentaacetic acid is described with numerous columns studies. The elutions are based on TALSPEAK liquid–liquid extraction chemistry, and provide high yield (> 90%), rapid, simple separations of the trivalent actinides from the lanthanides, which is often challenging due to similarities in chemical behavior among the trivalent f-block elements. Further, all three actinides can be separated from rare earth elements, including from massless fission product samples and samples with small amounts (~ 1–5 mg) of stable lanthanides. Separations with no detectable overlap between the actinide and lanthanide elutions is possible with massless samples, and in samples with mass high separation factors can be achieved (Am/Eu: 171; Am/La: 10 6 ).

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2026

Covalency of M–N Bonds in Isomorphous Lanthanide and Actinide 5-(2-Pyridyl)-1H-tetrazolate Complexes

Experimental and computational analyses of [M(pdtz) 3 (H 2 O) 3 ]·3.5H 2 O (M 3+ = Pu 3+ −Cm 3+ , La 3+ −Nd 3+ , and Sm 3+ −Ho 3+ , pdtz− = 5-(2-pyridyl)-1H-tetrazolate) were conducted to understand potential differences in bonding between lanthanide and actinide complexes with a N-donor ligand. Structural analyses show that the An−N bond distances in the Pu 3+ , Am 3+ , and Cm 3+ complexes are within error of one another. Whereas in the lanthanide series, there is a nearly linear decrease in the Ln−N bond lengths from La 3+ to Ho 3+ (excluding Pm 3+ ). The An−N bond lengths are ∼0.015 Å shorter than their similarly-sized lanthanide analogs, in agreement with computational results that suggest greater covalent character in these bonds versus those with lanthanides. QTAIM analysis indicates that the An−N orbital mixing remains essentially unchanged from Pu 3+ to Cm 3+ , consistent with the nearly identical An−N bond lengths. However, upon deconvolution of the NLMOs into orbital compositions, the metal orbital contributions to An−N bonding decreases slightly overall wherein the 6d involvement remains constant, 7s involvement slightly increases, and 5f participation decreases. The molecular orbital energy diagram indicates that energy degeneracy between the 5f metal and 2p ligand orbitals increases from Pu 3+ to Cm 3+ and counteracts the contraction of the 5f orbtials. Together with prior reports of decreasing energy degeneracy between 5f and 3p orbitals from Np 3+ to Cf 3+ , these observations provide guidance on understanding how chemical bonding evolves in the actinide series.

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

Tetraphenylpentalenide organolanthanide complexes

Lanthanide sandwiches of the D 2h 1,3,4,6-tetraphenylpentalenide are reported. The Ph 4 Pn dianion shows promise for new electron-rich f-block organometallics using the metal's d z 2 orbital, in contrast to the more widely used cyclooctatetraenyl dianion.

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

Catalytic Ambient Temperature Dinitrogen Conversion to a Bis(silyl)amine by Mononuclear Group 4 Aryloxide Complexes

The homogeneous conversion of ambient dinitrogen to amine products via the N2 reduction reaction (N2RR) remains a prized yet challenging feat for d-block complexes and is scarcely reported for f-block complexes. New, mononuclear TiIV and ZrIV aryloxide complexes Ti(DP)2 (1Ti), Zr(DP)2 (1Zr), and DP = [2-(OC6H2-2-tBu,4-Me)2CHPh] produce up to 51 eq. and up to 7.0 eq. of HN(SiMe3)2 per Ti/Zr, from N2, K0, weak acid, and chlorotrimethylsilane. Complex 1Ti exhibits more than double the activity toward N2-silylation of any previously reported Ti N2RR catalyst and can also catalyze the formation of up to 19 eq. of NH3, a new feature in early metal N2RR chemistry. The mononuclear 1Zr is the most active Zr catalyst for N2-silylation to date. [KSm(DP)2(THF)3] (1Sm), the mononuclear analogue of our previously reported dinuclear A-Sm complex, displays only stoichiometric N2-silylation due to its vulnerability to deleterious side reactions. DFT calculations confirm the catalysis can proceed via a monomeric Ti complex with a terminally bound, activated N2, agreeing with experimental 1H DOSY NMR measurements; the N-H bond is formed first, directing the catalyst selectivity. The isolable reduction product [K3(THF)Ti(DP)(DP-)(N2)] is also an active catalyst, and an intermediate in the calculated cycle.

Hernandez, Matthew↗
DOE OSTI2024

Efficient Parameterization of Density Functional Tight-Binding for 5 f -Elements: A Th–O Case Study

Density functional tight binding (DFTB) models for f-element species are challenging to parametrize owing to the large number of adjustable parameters. The explicit optimization of the terms entering the semiempirical DFTB Hamiltonian related to f orbitals is crucial to generating a reliable parametrization for f-block elements, because they play import roles in bonding interactions. However, since the number of parameters grows quadratically with the number of orbitals, the computational cost for parameter optimization is much more expensive for the f-elements than for the main group elements. In this work we present a set of efficient approaches for mitigating the hurdle imposed by the large size of the parameter space. A novel group-by-orbital correction functions for two-center bond integrals was developed. With this approach the number of parameters is reduced, and it grows linearly with the number of elements, maintaining the accuracy and the number of parameters, in the case of f elements, by more than 40%. The parameter optimization step was accelerated by means of the mini-batch BFGS method. This method allows parameter optimizations with much larger training sets than other single batch methods. A stochastic optimizer was employed that helped overcome shallow local minima in the objective function. The proposed algorithm was used to parametrize the DFTB Hamiltonian for the Th–O system, which was subsequently applied to the study of ThO 2 nanoparticles. The training set consisted of 6322 unique structures, which is barely feasible with conventional optimization methods. The optimized parameter set, LANL-ThO, displays good agreement with DFT-calculated properties such as energies, forces, and structures for both clusters and bulk ThO 2 . Benefiting from the fewer number of parameters and lower computational costs for objective function evaluations, this new approach shows its potential applications in DFTB parametrization for elements with high angular momentum, which present a challenge to conventional methods.

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

Optical properties of semiconductor nanoparticles doped with 3d and 4f block elements

Doped inorganic nanoparticles (NPs) have enabled researchers across multiple disciplines to create new materials with unique optical, electronic, magnetic, electrical, chemical, and/or compositional properties. In the quest for generating newer functional materials with controlled optical and electronic properties, the use of d- and f-block elements as dopants in the inorganic NPs remain at the forefront of research. This article summarizes experiments that identify the important control parameters, in the form of NP core and surface properties, for promoting host-sensitized dopant emission from d- and f-doped inorganic/semiconductor NPs. We conclude that energy offsets between the dopant and NP electronic levels and an understanding of the charge trapping mechanisms can be used to predict dopant luminescence, and we claim that these features can be used to choose NP host materials by design, rather than by trial and error.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗