f-block chemistry

Efficient separation of americium from lanthanides is crucial for reducing nuclear waste radiotoxicity, yet highly challenging owing to the chemical similarities of Am(III) and Ln(III) ions. Here, the authors review advancements in the preparation and stabilization of higher-valent americium states, highlighting coordination chemistry strategies that enhance Am/Ln separation efficiencies.

In-depth understanding of the bonding characteristics of the lanthanide ions in contemporary lanthanide-based materials is mandatory for tailoring their properties for novel applications. Here, the authors elaborate on open questions regarding the bonding situation in mainly molecular lanthanide (4f) compounds, where, as compared to their actinide (5f) analogs in which covalency of the bonds is a common feature, this is still under discussion for the 4f compounds.

Understanding the biogeochemistry of radionuclides in the environment is essential for effective isolation of nuclear waste in repositories, management of contaminated sites, ensuring long-term protection of our ecosystems, and limiting impacts on human health. Here the authors discuss the extreme complexity of this multidimensional chemistry problem, highlighting the outstanding open questions for the next generations of environmental radiochemists.

Over the past decade, momentous progress has been made in the characterization of late actinide compounds. Here the authors highlight how advances in spectroscopic and computational tools have developed our understanding of fundamental transplutonium bonding interactions, and discuss whether covalency and heterogeneity changes in 5f-orbital bonding could be harnessed in environmentally and industrially relevant systems.

It is well established that a significant amount of heat produced in the Earth’s mantle is due to the decay of uranium, yet the incorporation of uranium in deep mantle phases remains poorly explored. Here, two chemically simple uranium carbonates (U₂[CO₃]₃ and U[CO₃]₂) were synthesized by a reaction of UO₂ with CO₂ at lower mantle conditions, revealing that uranium carbonates could be host phases of uranium in carbon-rich lithologies in the Earth’s mantle.

Monoclinic zirconia (m-ZrO₂) serves as a crucial barrier against radionuclide release in nuclear fuel Zircaloy cladding, yet the effects of minor actinide incorporation and chemical reactivity remain unclear. Here, the authors reveal that americium enters m-ZrO₂ tetravalently with limited solubility and influences phase transformations, offering insights into behavior of minor actinides in spent nuclear fuel materials.

Luminescent lanthanide materials are of value for a range of applications, but most rely on intrashell f–f transitions, limiting their tunability. Here, the authors explore f–d transitions in three-coordinated cerium(III) complexes, achieving orange d–f emissions with photoluminescence quantum yields of up to 62%.

Electric fields can be used to manipulate molecular spin qubits, but the mechanisms underlying spin-electric coupling are not well understood. Here, the authors investigate the influence of hyperfine coupling between electron and nuclear spins on the mechanism of spin-electric coupling in a 4f molecular qudit.

Single-molecule magnets offer potential for high-density data storage, but their low blocking temperatures due to quantum tunneling of magnetization (QTM) remain a challenge. Here, the authors synthesize two dinuclear Er-cyclooctatetraenyl compounds, demonstrating that strong axial dipolar interactions effectively suppress QTM, achieving hard magnetic behavior with open hysteresis loops up to 10 K.

Following the Great East Japan earthquake and tsunami in 2011, reactor core overheating and fuel melting in the Fukushima Daiichi Nuclear Power Station produced microparticles from vaporized and rapidly solidified nuclear material for which chemical structures remain underexplored. Here, the authors present synchrotron-based X-ray absorption fine structure and X-ray diffraction studies of microparticles recovered from inside Unit 2 of the station, identifying uranium-rich particles with cubic UO2 and mixed U-Zr oxides with tetragonal ZrO2, the latter indicating rapid cooling from a high-temperature metastable phase above 1650 °C.

The structural flexibility of langbeinite-type structures to host different cations makes them suitable candidates for the formation of multicomponent actinide nuclear waste forms, but this approach remains underexplored. Here, the authors use an optimized high-temperature molten salt method to synthesize a series of single crystals of Cs₂U^ⅣLn(PO₄)₃ (Ln = Ce – Nd and Sm – Lu) that can simultaneously immobilize U, Ln, and Cs with enhanced leaching resistance.

Lanthanide sandwich complexes display interesting properties for diverse applications. Here, the authors synthesize monomeric and polymeric yttrium and erbium complexes ligated by cyclooctatetraendiide and stannolediide ligands and explore the magnetic properties of the erbium compounds.

Although Mn-site doping in LiMn₂O₄ mitigates Mn³⁺ -induced Jahn-Teller distortion responsible for cathode degradation in Li-ion batteries, this strategy faces inherent trade-offs, with low-valent doping weakening oxygen bonding and high-valent doping increasing the Mn³⁺ content. To address these limitations, the authors propose dual-lanthanide (La³⁺/Ce³⁺) co-doping and show that La³⁺ -Ce³⁺ cooperation mitigates Mn dissolution while stabilizing the spinel framework, with Ce ions additionally boosting conductivity.

Lanthanides have been identified as biologically essential metals, crucial in the active sites of alcohol dehydrogenase (ADH) enzymes in methylotrophic bacteria. Here, the authors demonstrate that trivalent actinide ions, including actinium, americium, curium, berkelium, and californium, can substitute lanthanides in ADHs and support bacterial growth.

Understanding the reactivity of actinyl-peroxide complexes is critical for predicting the behavior of spent nuclear fuel in radiolytic environments. Here, the authors synthesize and characterize a lithium neptunyl(VI) hydroxo-peroxo phase that stabilizes superoxide and underscores the importance of secondary-sphere coordination in modeling actinyl–peroxide compounds.

Organoactinides are known to catalyze the hydroboration of carbonyl-containing molecules, however, the optimization of ligands to tune the catalytic properties of actinide complexes remains underexplored. Here, the authors synthesize thorium and uranium complexes with six-membered N-heterocyclic iminato ligands, demonstrating their catalytic efficiency in ester hydroboration, and further accelerating the reaction by actinide–alkoxide activation.

The calorimetric determination of enthalpies of mixing in multi-component molten salt systems often relies on empirical models that lack physically interpretable parameters. Here, the authors use the molecular interaction volume model (MIVM) to integrate experimentally measured enthalpies and solvation structures from ab initio molecular dynamics simulations to extrapolate excess Gibbs energy and determine the compositional dependence of La³⁺ activity in the LaCl₃-(LiCl-KCl) system.

Lanthanide complexes hold promise for emission lifetime-based thermometers, but their temperature sensitivity is often limited by long-lived ligand triplet states. Here, the authors introduce a dinuclear Tb(III)–Nd(III) complex that displays a temperature sensitivity of 4.4% K⁻¹ owing to efficient energy transfer pathways.

The exact crystal chemistry of perovskites containing 5f elements has remained a matter of debate. Here, the authors synthesise a BaO-deficient Pu-based perovskite with a composition close to Ba3PuO6 and study the Pu oxidation state, the crystal structure and Ba/Pu ratio, reporting on thermodynamic and magnetic properties and offering new insights into Ba-Pu-O solid-state chemistry.

Understanding the electronic structure of the actinide series is critical for advancing the nuclear fuel cycle. Here, the authors explore a series of isostructural An(COT^big)₂ (An = Th, U, Np, Pu) complexes with clam-shell geometries, where structural and electronic characterization highlights the impact of f-orbital contributions in actinide bonding.

Iminophosphoranomethanide ligands have been used to stabilize metal complexes, but their application as alkyl precursors in deprotonation reactions remains unexplored. Here, the authors prepare and characterize bis- and tris- methanide alkaline and rare earth complexes through protonolysis between dibenzyl metal precursors and the CH₂(SiMe₃)P(Ph)₂ = NSiMe₃ proligand or salt elimination reactions, and show that rare earth methanides can be used as synthetic precursors for the preparation of solvent-free complexes.

Rare earth element (REE) extraction and separation are crucial for sustainable resource management, yet efficient methods remain limited. Here, the authors append macrocyclic chelator BZmacropa to a solid resin and demonstrate selective REE extraction and separation with high purity and recyclability, offering a promising solution for REE recovery from complex mixtures and waste streams.

Lanthanide coordination compounds have demonstrated potential as molecular thermometers, but little attention has been paid to their performance in the physiological temperature range within biological radiation windows. Here, the authors explore the thermometric properties of three Nd^III complexes within the physiological temperature range operating in the first two biological windows, finding anti-thermal quenching effects that contribute to the thermometric performance.

Gadolinium-based contrast agents are the gold standard for magnetic resonance imaging (MRI), however, their poor stability causes safety problems in clinical applications. Here, the authors develop two chiral Gd(III) DOTA-based complexes with a macrocyclic backbone that show higher relaxivities and stabilities than benchmark complexes.

Understanding adsorption reactions at solid–water interfaces is key to enabling important chemical separations; however, when such surfaces are confined in nanopores, nanoconfinement effects on surface chemistry are difficult to predict. Here, X-ray absorption fine structure spectroscopy and operando flow microcalorimetry are used to determine the effects of nanoconfinement on the energetics and coordination environments of trivalent lanthanides adsorbed on alumina surfaces within nanopores.

Luminescent lanthanide complexes are promising materials for use in displays and sensors, however, these materials often undergo thermal quenching. Here, the authors synthesize and characterize a terbium dinuclear phosphine oxide-bridged phenanthrene complex, which exhibits thermally-enhanced emission.

Monitoring of the hypertension drug felodipine is important to avoid unwanted side effects from high concentrations, but its sensitive detection remains challenging. Here, combining the advantages of ratiometric luminescence probes and near-infrared lanthanide luminescence sensing, multi-emission near-infrared magnetic core-shell nanoparticles based on lanthanide metal–organic frameworks are synthesized using a layer-by-layer method and shown to have excellent temperature and felodipine detection abilities.

Detection of trimethylamine N-oxide (TMAO) can allow for early intervention of cardiovascular disease, but is challenging to achieve using conventional materials and instruments owing to it being spectroscopically silent in the UV-visible region. Here, a series of bilanthanide metalorganic frameworks functionalised with a borono group are shown to detect TMAO with high sensitivity and selectivity by exploiting the inverse emission intensity changes of the two lanthanide centres.