105 Search Results

Stimuli-responsive changes in lanthanide-based materials are a promising research direction. In this study, [DBTTF]₄[Ce₂Cl₁₀] DBTTF = dibenzotetrathiafulvalene (1) was synthesized by a light-induced crystallization, where photo-oxidation of DBTTF enables formation of the cerium dimer [Ce₂Cl₁₀]⁴⁻. Intermolecular interactions between the stacked organic units of the crystal result in charge transfer bands in the visible-NIR (near-infrared) region, evident in the solid-state absorption spectrum upon comparison with the solution spectrum. The assignments of the sublattice oxidation states were made with single-crystal X-ray diffraction (SC-XRD) structural characterization, Raman spectroscopy, X-ray absorption spectroscopy, and magnetometry. Continuous 532 nm laser irradiation of the microcrystalline solid modulatesmore » the redox states in 1, leading to ∼40% reduction in the observed magnetization at 2 K. Density functional theory PBE+U/HSE06 band structure calculations predict Mott insulating behavior in 1, with a bandgap of 0.54/0.81 eV, and further support the conjecture that the observed photo-induced change in magnetization results from electron transfer from the [Ce₂Cl₁₀]⁴⁻ anions to the π-stacked [DBTTF]₂²⁺ organic dimer subunits. An enhancement in conductivity is similarly observed upon 532 nm irradiation, determined by single-crystal transport measurements. The findings reveal that photo-responsive lanthanide-based materials can be achieved by integration of redox-active organic moieties with redox-active lanthanide cations for the realization of switchable, photo-magnetic materials.« less

Single crystals of LnFe(SO₄)₃(H₂O)₂ (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm; compounds 1–11) and LnFe(SO₄)₃(H₂O) (Ln = Tm, Yb, Lu; compounds 12–14) were synthesized under hydrothermal conditions. Single-crystal X-ray diffraction (SCXRD) analysis revealed that the dihydrated compounds (1–11) crystallize in centrosymmetric (CS) structures, with the lanthanide ions adopting eight-coordinate geometries. In contrast, the monohydrated compounds (12–14) exhibit noncentrosymmetric (NCS) structures, where the lanthanide ions are seven-coordinated. Vibrating sample magnetometry (VSM) confirmed that compounds 2, 4, and 7–11 are paramagnetic below 400 K, with compound 8 displaying the highest magnetic susceptibility. Compounds 1, 5, 6,more » 13, and 14 show a sharp increase in magnetic susceptibility at Néel temperatures (T_N) of approximately 72, 76, 70, 58, and 56 K, respectively, indicating antiferromagnetic ordering. High-temperature magnetic susceptibility measurements further support the presence of antiferromagnetic transitions in these compounds. Second harmonic generation (SHG) measurements showed that the noncentrosymmetric Yb (compound 13) and Lu (compound 14) compounds exhibit SHG intensities of 0.3× and 1.6× that of potassium dihydrogen phosphate (KDP), respectively.« less

Rare earth elements (REEs) are critical for the development of a range of new technologies. However, the current industrial separation processes of these metals from natural sources, recycled materials, and industrial effluents involve the large consumption of organic solvents, resulting in a sizable environmental footprint. We aim to exploit the high affinity of the block V peptide of the repeats-in-toxin (RTX) domain of the adenylate cyclase protein from Bordetella pertussis for the separation of REEs. This peptide selectively binds with lanthanide (Ln) cations and can undergo Ln-induced phase separation, which can be used in bioseparation processes. Here, we evaluated themore » self-assembling structures of complexes of the RTX domain peptide folded in the presence of Ln³⁺ cations. Size distribution and surface potential measurements of complexes were taken to understand the Ln-induced changes in the complexed peptide. Transmission electron microscopy imaging was used to explore the structures of complexes, while anomalous small-angle X-ray scattering measurements were used to determine the distribution of Ln³⁺ ions within the protein-based macrostructures. In the presence of excess Ln³⁺, we observed the formation of coral-like cylindrical structures comprised of Ln³⁺-RTX complexes, with approximately eight trivalent metals per peptide within the nanosized assemblies. These findings provide new insights into the structural organization of assembled RTX domains and their ability to coordinate with REEs, forming nanosized, metal-rich structures that naturally condense, providing a proof-of-concept for protein-based separation processes of these critical materials.« less

A set of nine new robust, tunable cerium complexes supported by an ansa-bis(cyclopentadienyl) ligand, [Me₂Si(η⁵-Cp^R)₂]CeX (^anCp^R)CeX, are excellent homogeneous visible-light photocatalysts for the monodefluoroalkylation of trifluorotoluene with Mg(CH₂C₆H₅)₂THF₂ (R = Me₄, SiMe₃, X = N(SiMe₃)₂ (N″), X = CH(SiMe₃)₂ (R''), Cl, OC₆H₂^tBu₂-2,6,Me-4 (OAr)). The trends in photocatalytic activity within the series are explained by photophysical spectroscopic analyses. The aryloxide complex [Me₂Si(Cp^SiMe3)₂]CeOAr, which has the highest activity (95% substrate conversion in 27 h), shows the most negative (most reducing) excited-state reduction potential (-2.71 V vs Fc). The precatalyst excited-state lifetimes are also exceptionally long. Detailed photoluminescence, NMR spectroscopic, and kinetic studiesmore » on chloride [Me₂Si(Cp^Me4)₂]CeCl suggest that the "ate" complex [{Me₂Si(Cp^Me4)₂}₂Ce^IIIClBn][MgBn] is the active catalyst in the alkylation reaction to form PhCF₂CH₂Ph with high selectivity over PhCF₂H. Finally, the reaction rates are up to 30 times higher than previously reported for organometallic rare-earth photocatalysts for these Ce complexes and comparable to established Ir-based photoredox systems.« less

Lanthanide ions are difficult to separate from one another due to their similar chemical properties. The discovery of lanthanide-binding peptides and proteins in nature has led to an increased interest in the possibility of utilizing the strong binding of peptides to lanthanide ions for their separations; as such, there has been an effort to identify or design peptides with improved lanthanide binding and selectivity toward particular lanthanide ions. Here, in this study, we designed and characterized lanthanide-binding cyclic peptides (LBCPs) with molecular dynamics simulations, electronic structure calculations, and emission spectroscopy. Luminescent decay measurements were done to determine the number ofmore » water molecules coordinated to the Eu³⁺ ion in Eu-LBCP complexes and compare to the predicted number of water molecules by computation to assess the lanthanide-binding affinity of LBCPs. Measured stability constants show binding of the LBCPs to the Eu³⁺ ion with stronger than micromolar affinity. We were able to identify multiple peptides that selectively bind to middle lanthanides. We describe the structural basis of the lanthanide-binding selectivity trend with strongest binding to the middle lanthanides, followed by the heavier lanthanides, and finally to the lighter ions.« less

Lanthanides (Lns) are important to many technologies including magnets used in high-efficiency traction motors and generators. While commonly occurring in the environment and industrial waste streams, Ln are generally present at low concentrations. This work demonstrates synergistic Ln recovery from an aqueous magnet leachate to single ppm concentrations using Na₂SO₄ addition and subsequent dimethyl ether-driven fractional crystallization (DME-FC) treatment. It is found that combining DME-FC with low concentrations of Na₂SO₄ (≈0.1 M) results in synergistic isolation of Lns while making use of Na₂SO₄, an excessive byproduct of hydrometallurgical metal production. Combined Na₂SO₄ + DME reduces Ln metal ion (Pr, Nd,more » Sm, Gd, Dy, and Ho) solubilities by 700–27,000x with final concentrations ranging from 2 ppm to 200 ppm. Separately, Na₂SO₄ 0.1 M provides a 10–200x reduction and DME provides a 90–1,400x reduction in Ln solubilities. Final Ln concentrations of the combined process are 99.8% lower than what is achieved with each individual process.« less

Ligand-appended pillar[5]arene (LAP) channels are emerging as a promising platform for ion-selective membranes. In this study, we investigated the ion selectivities of three LAP channels functionalized with distinct ligands: diglycolamine, carbamoylmethyl phosphine oxide, and propionamide phosphonic acid. These ligands were chosen based on their demonstrated affinities for lanthanides in solvent extraction studies. We examined the selectivity of each channel toward a series of monovalent, divalent, and trivalent ions: Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, La³⁺, Eu³⁺, and Yb³⁺. To quantify ion-channel interactions and the energetics of translocation, we computed the potential of mean force (PMF) profiles for each ion. These PMFsmore » were subsequently recast into permeability coefficients, enabling a direct evaluation of ion permselectivity. Our results reveal distinct selectivity patterns governed by the chemical nature of the appended ligands. The diglycolamine-functionalized channel exhibits strong interactions with monovalent ions, leading to replication of the Li⁺ bulk hydration shell within the channel. This promotes preferential transport Li⁺ ions while effectively excluding divalent and trivalent species. In contrast, the carbamoylmethyl phosphine oxide-functionalized channel displays a reduced selectivity between monovalent ions while similarly exhibiting an effective rejection of divalent and trivalent ions. This arises from steric hindrance around channel-lining oxygens imposed by the ligand's bulky phenyl groups which limits heavy ion coordination and promotes retention of hydration shells effectively increasing effective ion size. The propionamide phosphonic acid-functionalized channel exhibits a different trend, favoring ions with lower hydration free energies, with K⁺ ions showing enhanced permeation. These findings highlight the critical role of ligand-ion interactions in modulating ion selectivity within LAP channels. In particular, the strong coordination exhibited by diglycolamine and propionamide phosphonic acid ligands significantly influences the ion transport energetics and selectivity profiles.« less

A sustainable and robust supply chain of rare earth elements (REEs) is necessary to meet our consumer, national security and clean energy goals. However, current intra-REE separation technologies (e.g. solvent extraction) are costly and carry a heavy environmental burden. Therefore, the development of new aqueous based ligands that are selective for individual REEs will be integral in future REE production systems. To develop these ligands, an understanding of how ligand coordination structure relates to selectivity is imperative. We used X-ray absorption spectroscopy (XAS) to observe the local structure around four lanthanide (Ln) ions (La, Ce, Pr and Nd) complexed bymore » water and several relevant chelating ligands [lanmodulin EF-hand 1 peptides (LanM1), ethyl­enedi­amine­tetra­acetic acid (EDTA), amino­tris­(methyl­ene­phospho­nic acid) (ATMP) and citric acid]. To collect these liquid-phase XAS spectra, we developed a new flow cell that prevents bubble interference and beam damage to the samples. In the X-ray absorption near-edge structure (XANES), we observed energy shifts in the white line, white line broadening and differences in the white line intensity of different Ln–ligand complexes between ligands. In the extended X-ray absorption fine structure (EXAFS), we distinguished differences in peak intensity and distance between coordinating ligands. Differences in the local coordination structure between Ln–LanM1 peptide complexes were more subtle compared with the other ligands (La–water, La–EDTA, La–ATMP and La–citric acid complexes). Further XANES and EXAFS studies, in combination with modelling and other techniques, could greatly improve our structural knowledge of how these aqueous ligands bind Ln ions and how they can be used to design more selective ligands for more efficient and sustainable REE separations.« less

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 Ln₂(OPS(OEt)₂)₆(H₂O)₈ (Ln = La) (La₂L₆H₂O), Ln₂(OPS(OEt)₂)₆(EtOH)₄ (Ln = La) (La₂L₆EtOH), K₂[Ln(OPS(OEt)₂)₅(H₂O)₂]·H₂O·CH₂Cl₂, (Ln = Ce) (CeL₅-α), K₂[Ln(OPS(OEt)₂)₅(H₂O)₂]·H₂O·CH₂Cl₂, (Ln = Pr) (PrL₅-β), K[Ln(OPS(OEt)₂)₄(H₂O)₃], (Ln = Pr, Sm-Er) (ML₄), and K₃[Ln(OPS(OEt)₂)₆], (Ln = Dy) (DyL₆) were synthesized and characterized using single-crystal X-raymore » 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 Ln³⁺ cations.« less

Nitrate-decorated hexamers with a [Ln₆(μ₆-O)(μ₃–OH)₈]⁸⁺ core have been reported for nearly every lanthanide ion and are used as precursors for the assembly of functional metal–organic frameworks. Yet, few studies have examined the correlation between the solution and solid-state species, and the formation of mixed-metal clusters. Toward this end, a series of homo- and heterometal lanthanide nitrate hexamers was prepared via pH adjustment of aqueous lanthanide nitrate solutions. Examination of the homometallic europium solutions using Small Angle X-ray Scattering and nESI-MS showed that lower order complexes dominate lanthanide speciation in nitrate media. Yet, powder X-ray diffraction data of the precipitated phasemore » confirmed the formation of [Ln₆(μ₆-O)(μ₃-OH)₈(NO₃)₆(H₂O)₁₂]·2(NO₃)·n(H₂O), Ln₆, for Ln = Eu and Tb. For heterometal systems, analysis of the solid-state product by ICP–MS showed the selective incorporation of the heavier rare earths into Ln₆. Selectivity was quantified by calculating an average separation factor, which is defined as the ratio of recovery factors of both metals. Further examination of the luminescence behavior of mixed metal [Tb_6–xEu_x(μ₆-O)(μ₃-OH)₈(NO₃)₆(H₂O)₁₂]·2(NO₃)·n(H₂O), with x = 1.1–3.6, showed that the relative intensities of the peaks at 489 nm (terbium, ⁵D₄ → ⁷F₆) and 690 nm (europium, ⁵D₀ → ⁷F₄) trend with the percent incorporation of europium and terbium into the cluster.« less