Rare Earth Metal Cations Research Articles

Persistent luminescent nanoparticles: Challenges and opportunities for a shimmering future

Persistent phosphors are luminescent sources based on crystalline materials doped with rare-earth or transition metal cations able to produce light after the excitation source vanishes. Although known for centuries, these materials gained renewed interest after the discovery of Eu2+,RE3+ co-doped aluminates and silicates in the late 1990s due to their unprecedented afterglow properties. In contrast, persistent nanophosphors have emerged only recently as a nanoscale alternative to their bulk counterparts, offering exciting opportunities of particular relevance for in vivo imaging, optical data storage, or unconventional light generation. However, taking advantage of the avenues opened by nanoscience demands developing new synthetic strategies that allow precise control of the morphology, surface, and defect chemistry of the nanomaterials, along with a profound understanding of the physical mechanisms occurring in the nanoscale. Besides, advanced physicochemical characterization is required to assess persistent luminescence in a quantitative manner, which allows strict comparison among different persistent nanophosphors, aiming to propel their applicability. Herein, we revisit the main phenomena that determine the emission properties of persistent nanoparticles, discuss the most promising preparation and characterization protocols, highlight recent achievements, and elaborate on the challenges ahead.

Novel mixed ligand coordination compounds of some rare earth metal cations containing acesulfamato/N,N-diethylnicotinamide.

The mixed ligand coordination compounds containing acesulfamato and N,N -diethylnicotinamide biomolecules of some rare earth metal cations (Eu3+, Tb3+, Ho3+, Er3+ and Yb3+) were synthesized, and their structural properties were investigated. Possible structural formulas have been proposed by determining the chemical composition of molecules (elemental analysis), binding properties (infrared spectroscopy, mass analysis, solid-state UV-vis spectroscopy), thermal degradation properties (TGA / DTA curves). Based on the data collected, it is suggested that rare earth metal cations with a 3+ oxidation state have sextet coordination. The geometries of the structures were thought to be distorted octahedral. The charge balance of the coordination sphere is balanced by a monoanionic acesulfamato located outside the coordination sphere. When the thermal behaviours of the complexes were examined, it was determined that the compounds with Eu3+, Tb3+, and Yb3+ metal cations contained one hydrate water outside the coordination sphere. Hydrate waters do not exist in the Ho3+ and Er3+ metal cation-centred complexes. At the end of the thermal decomposition analysis of all complex structures, it was determined that they leave the relevant metal oxides in the reaction vessels as final decomposition products.

Multicomponent Cooperative Assembly of Nanoscale Boron-Rich Polyoxotungstates with 22 and 30 Boron Atoms

This work demonstrates that the introduction of positive lanthanide (Ln) and transition metal (TM) cations into polyoxotungstates (POTs) to stabilize negative oxoboron clusters is a feasible and ge...

High-pressure synthesis of REB5O8(OH)2 (RE = Ho, Er, Tm)

Abstract The rare earth oxoborates REB5O8(OH)2 (RE = Ho, Er, Tm) were synthesized in a Walker-type multianvil apparatus at a pressure of 2.5 GPa and a temperature of 673 K. Single-crystal X-ray diffraction data provided the basis for the structure solution and refinement. The compounds crystallize in the monoclinic space group C2 (no. 5) and are composed of a layer-like structure containing dreier and sechser rings of corner sharing [BO4]5− tetrahedra. The rare earth metal cations are coordinated between two adjacent sechser rings. Further characterization was performed utilizing IR spectroscopy.

Rare-Earth Metal Complexes of the Antibacterial Drug Oxolinic Acid: Synthesis, Characterization, DNA/Protein Binding and Cytotoxicity Studies.

“Drug repositioning” is a current trend which proved useful in the search for new applications for existing, failed, no longer in use or abandoned drugs, particularly when addressing issues such as bacterial or cancer cells resistance to current therapeutic approaches. In this context, six new complexes of the first-generation quinolone oxolinic acid with rare-earth metal cations (Y3+, La3+, Sm3+, Eu3+, Gd3+, Tb3+) have been synthesized and characterized. The experimental data suggest that the quinolone acts as a bidentate ligand, binding to the metal ion via the keto and carboxylate oxygen atoms; these findings are supported by DFT (density functional theory) calculations for the Sm3+ complex. The cytotoxic activity of the complexes, as well as the ligand, has been studied on MDA-MB 231 (human breast adenocarcinoma), LoVo (human colon adenocarcinoma) and HUVEC (normal human umbilical vein endothelial cells) cell lines. UV-Vis spectroscopy and competitive binding studies show that the complexes display binding affinities (Kb) towards double stranded DNA in the range of 9.33 × 104 − 10.72 × 105. Major and minor groove-binding most likely play a significant role in the interactions of the complexes with DNA. Moreover, the complexes bind human serum albumin more avidly than apo-transferrin.

A review on dry reforming of methane over perovskite derived catalysts

Dry reforming of methane (DRM) is widely studied as one of the potential routes for syngas production from two greenhouse gases (CH4 & CO2) and can reduce the net emission of these gases if the energy used for it is derived from non-hydrocarbon source. Many conventional metal/support catalyst systems, though are highly active, deactivate within few hours due to surface coke deposition or sintering of the active metal clusters. In order to overcome these challenges and withstand the extreme operating temperatures of DRM, active metals can be incorporated into crystalline oxides like perovskites, pyrochlores, hydrotalcites and hexaaluminates. These metal-containing oxides, once the active metal is reduced, produce a highly dispersed active catalyst.This review emphasizes the application of perovskite-derived catalysts in dry reforming of methane. Perovskites are crystalline oxides with general formula of ABO3, where A is generally a rare earth, alkaline earth or alkali metal cation while B is a transition metal cation. The exsolution process involved in the reduction of perovskite catalysts produces smaller size metal particles which in turn dictate the superior catalytic performance of these materials. Preparation methods, “A” and/or “B” site partial substitutions and additional use of high surface area supports (like mesoporous silicates and basic oxides) for dispersing perovskite catalysts, greatly influence the physicochemical and catalytic behavior of these perovskite derived catalysts. “A” site substitutions generally enhance the oxygen mobility in the perovskite structure by generating oxygen vacancies which suppress the carbon deposition, while bimetallic synergistic effects are produced by addition of a second metal at the “B” site which tend to increase the activity and stability of these catalysts. This review also includes a detailed discussion on the mechanism of DRM in perovskite derived catalysts.

Praseodymium cation (Pr+) reactions with H2, D2, and HD: PrH+ bond energy and mechanistic insights from guided ion beam and theoretical studies.

Guided ion beam tandem mass spectrometry was used to study the reactions of the atomic lanthanide praseodymium cation (Pr+) with H2, D2, and HD as a function of collision energy. Modeling the kinetic-energy-dependent endothermic reactions to form PrH+ (PrD+) yields a 0 K bond dissociation energy (BDE) of 2.10 ± 0.05 eV for PrH+. Quantum chemical calculations were performed for PrH+ at the B3LYP, BHLYP, PBE0, and coupled-cluster with single, double, and perturbative triple levels of theory, and they overestimate the PrH+ experimental BDE by 0.06 -0.28 eV. The branching ratio of the PrH+ and PrD+ products in the HD reaction suggests that the reaction occurs via a direct reaction mechanism with short-lived intermediates. This is consistent with the theoretical calculations for the relaxed potential energy surfaces of PrH2 +, where no strongly bound dihydride intermediates were found. The reactivity and PrH+ BDE are compared with previous results for lanthanide metal cations (La+, Ce+, Sm+, Gd+, and Lu+). Periodic trends across the lanthanide series and insights into the role of the electronic configuration on metal-hydride bond strength are discussed.

Synthesis of mesoporous silica containing group 2-metal cations and their performance behavior in rare earth cation adsorption

Herein, mesoporous silica was prepared using the co-precipitation process by adding Mg, Ca, or Sr. The specific surface areas of silica were maintained with the incorporation of Mg or Ca substitutes with several tens mol%; however, they were observed to decrease significantly due to the Sr substitution. Further, the applicability of Mg, Ca, and Sr as modifiers was estimated using XPS spectra. The simultaneous ion-exchange in the mesoporous silica hybrids was confirmed by testing an aqueous solutions containing 12 coexisting rare earth metal cations. A higher degree of adsorption was obtained as the ionic radius of the cations decreased. In addition, the concave tetrad effect demonstrated that adsorption occurred through the ion-exchange reaction at specific active sites. To investigate the kinetics of the ion-exchange reaction, rate constants were estimated from time-dependency measurements. The measured rate constants for the hybrids were approximately 5.4×10-3, 5.2×10-3, and 1.5×10-3 min−1, for Mg, Ca, and Sr, respectively. Silica hybrids containing Mg and Ca exhibited mesoporous structures that proved to be advantageous on accelerating the reaction rates obtained for lanthanoid adsorption.

Acesulfame complex compounds of some lanthanide group metal cations. Synthesis and characterization

Some rare earth metal cations (Eu3+, Tb 3+, Ho3+, Er 3+ and Yb3+) of the acesulfame ligand and complex compounds were synthesized by hydrothermal method. Elemental analysis, infrared spectroscopy, mass analysis and solid-state UV–vis spectroscopy methods were used for the structural characterization of these compounds. In addition, TGA curves were recorded to determine the thermal degradation steps and possible degradation products of complex structures. As a result of the analysis of the structures, it was determined that the load equivalence of the metal cations having +3 oxidation steps provided with three monoanionic acesulfame ligands included in the structure. Rare earth elements, which have high coordination due to their large radii, are thought to exhibit hexadecimal coordination in synthesized molecules. The coordination sphere is complemented by two acesulfame and 2 aqua ligands showing acidic -N and carbonyl oxygen binding to the bidentate. One acesulfame ligand is thought to be located outside the coordination sphere as a counter ion. According to the recorded TGA curves, all molecules were found to contain one hydrate water. It was determined by FT-IR analysis that all complex structures formed the metal oxides in the reaction vessels as thermal decomposition products.

Unique synthesis, structure determination, and optical properties of seven new layered rare earth tellurite nitrates, RE(TeO3)(NO3) (RE = La, Nd, Eu, Gd, Dy, Er, and Y)

Seven new rare earth tellurite nitrates, RE(TeO3)(NO3) (RE = La, Nd, Eu, Gd, Dy, Er, and Y), have been synthesized in closed autoclaves in the absence of solvent using TeO2 and corresponding rare earth metal nitrate hydrates. Although all the reported rare earth tellurite nitrates are stoichiometrically equivalent, the crystal structures are different. While RE1(TeO3) (NO3) (RE1 = La and Nd) crystallizing in the monoclinic space group, P21/n (No. 14) exhibit layered backbones composed of RE1O9, TeO3, and NO3 groups, RE2(TeO3)(NO3) (RE2 = Eu, Gd, Dy, Er, and Y), crystallizing in the orthorhombic space group, Cmca (No. 64) reveal layered frameworks consisting of RE2O8, TeO4, and NO3 units. The frameworks include infinite chains of (TeO3)n. Band gaps derived from the UV–vis diffuse reflectance spectral data for the title compounds range from 3.6 to 4.4 eV depending on the extent of 4d, 5d, and/or 4f orbitals of rare earth metal cations as well as the distortions arising from unsymmetrical tellurites. Other characterizations including infrared spectroscopy, thermal analyses, dipole moment calculations, and photoluminescence measurements are also discussed.

Remarkable Structural Diversity between Zr/Hf and Rare-Earth MOFs via Ligand Functionalization and the Discovery of Unique (4, 8)-c and (4, 12)-connected Frameworks.

Ligand modification in MOFs provides great opportunities not only for the development of functional materials with new or enhanced properties but also for the discovery of novel structures. We report here that a sulfone-functionalized tetrahedral carboxylate-based ligand is capable of directing the formation of new and fascinating MOFs when combined with Zr4+/Hf4+ and rare-earth metal cations (RE) with improved gas-sorption properties. In particular, the resulting M-flu-SO2 (M: Zr, Hf) materials display a new type of the augmented flu-a net, which is different as compared to the flu-a framework formed by the nonfunctionalized tetrahedral ligand. In terms of properties, a remarkable increase in the CO2 uptake is observed that reaches 76.6% and 61.6% at 273 and 298 K and 1 bar, respectively. When combined with REs, the sulfone-modified linker affords novel MOFs, RE-hpt-MOF-1 (RE: Y3+, Ho3+, Er3+), which displays a fascinating (4, 12)-coordinated hpt net, based on nonanuclear [RE9(μ3-Ο)2(μ3-ΟΗ)12(-COO)12] clusters that serve as hexagonal prismatic building blocks. In the absence of the sulfone groups, we discovered that the tetrahedral linker directs the formation of new RE-MOFs, RE-ken-MOF-1 (RE: Y3+, Ho3+, Er3+, Yb3+), that display an unprecedented (4, 8)-coordinated ken net based on nonanuclear RE9-clusters, to serve as bicapped trigonal prismatic building units. Successful activation of the representative member Y-ken-MOF-1 reveals a high BET surface area and total pore volume reaching 2621 m2 g-1 and 0.95 cm3 g-1, respectively. These values are the highest among all RE MOFs based on nonanuclear clusters and some of the highest in the entire RE family of MOFs. The present work uncovers a unique structural diversity existing between Zr/Hf and RE-based MOFs that demonstrates the crucial role of linker design. In addition, the discovery of the new RE-hpt-MOF-1 and RE-ken-MOF-1 families of MOFs highlights the great opportunities existing in RE-MOFs in terms of structural diversity that could lead to novel materials with new properties.

Recognition of Lanthanide Metal Cations by t‐DSMI@Alkyl‐Substituted Cucurbit[6]uril Probes

AbstractThe binding behavior of three different methyl‐substituted cucurbit[6]urils (SQ[6]s), namely hexamethylcucurbit[3,3]uril (Me6Q[3,3]), tri‐hydroxylated symmetrical hexamethylcucurbit[3,3]uril ((OH)3Me6Q[3,3]), and symmetrical tetramethylcucurbit[6]uril (TMeQ[6]) with trans‐4‐[4‐(dimethylamino)styryl]‐1‐methylpyridinium iodide (t‐DSMI) have been investigated. The results showed that the guest t‐DSMI exhibits dramatic fluorescence enhancement upon interacting with the three SQ[6]s to form 1 : 1 inclusion complexes. Upon addition of lanthanide metal cations to the three t‐DSMI@SQ[6] probes, the fluorescence of the guest was quenched to varying degrees. On this basis, it is possible to discriminate lanthanide metal cations with different ionic radii by principal component analysis (PCA).

Complexing properties of pyrenyl-appended calix[4]arenes towards lanthanides and transition metal cations

The binding properties of pyrenyl-appended calix[4]arenes 2–4 towards lanthanide and transition metal cations were investigated by spectrophotometric data processing, which indicated that 2 forms mononuclear species with all the cations studied. The extraction power decreased toward ligands 2–3 except Co2+, then increased for ligand 4, which reflect the better ability of ligands 2 and 4 to complex and extract at the interface. Derivative 3 formed mono and binuclear species simultaneously with the trivalent cations from La3+ to Er3+ but only M2L species with Yb3+. In the case of 4, only M3L was detected for Yb3+ and only ML for La3+, with the complexation of the other cations tending to form mono-, bi- and tri-nuclear species.

Triple Frustrated Lewis Pair-Type Reactivity on a Single Rare-Earth Metal Center.

Rare-earth metal cations have been used rarely as Lewis-acidic components in the chemistry of frustrated Lewis pairs (FLPs). Herein, we report the first cerium/phosphorus system (2) employing a heptadentate N4 P3 ligand, which exhibits triple FLP-type reactivity towards a series of organic substrates, including isocyanates, isothiocyanates, diazomethane, and azides on a single rare-earth Lewis acidic Ce center. This result shows that the Ce center and three P atoms in 2 could simultaneously activate three equivalents of small molecules under mild conditions. This study broadens the diversity of FLPs and demonstrates that rare earth based FLP exhibit unique properties compared with other FLP systems.

Изучение растворимости осадков некоторых лантаноидов в карбонатных средах

The study examines the dissolution process for the precipitates of the rare-earth carbonates and phosphates with a change in the concentration parameters of the system. The objective of the study is to determine the nature of the dissolution process at variable composition of the studied solutions. As a result of the theoretical base analysis, the qualitative and quantitative content of rare-earth metals in red sludge and phosphogypsum is presented, which governs the interest in this problem under consideration. The available techniques for extraction of rare-earth metals from red sludge and phosphogypsum have also been considered, their advantages and disadvantages are presented. A promising carbonate-alkali method for the extraction of rare-earth metals has been considered. Thermodynamic parameters of the system have been calculated to determine the possibility of the process. During the experiment the factors affecting the dissolution process have been examined: the carbonate ion concentration, the nature of the solvent cation and rare-earth metal cation. Carbonates and phosphates of europium, holmium, and neodymium have been considered as the analyzed components. Carbonates and phosphates of neodymium, europium, and holmium have been dissolved in model solutions of K2CO3 with the concentrations of 0.2–4.5 mol/L until reaching equilibrium. The obtained results show the dependence of solubility of the precipitates of rare-earth metals on the solvent nature and concentration. The explored data are presented as solubility isotherms. On the basis of experimental data the values of the extraction degree of a rare-earth metal into the solution have been calculated. For neodymium, europium, and holmium carbonates, the maximum recovery degree αmax is 72.8 %, 81.2 %, 83.0 %, respectively. During the experiment with dissolution of lanthanide phosphates, the following results have been obtained: the maximal degree of neodymium extraction is 60.59%, while for europium it equals 51.66 % and 93.01 % for holmium

Обоснование перспективности использования фосфатотитановых ионитов для извлечения из растворов радионуклидов редкоземельных металлов

The results of a study of the sorption properties of ion-exchange materials based on hydrated titanium (IV) oxohydroxophosphates with respect to rare-earth metal cations are presented in this paper. A high affinity of the latters for the sorption matrix in nitrate media was established, which is determined by the ion radius of the sorbate and increases in the series Y3+  Gd3+  Eu3+ Sm3+ Nd3+ Ce3+ at pH=4 and La3+  Ce3+  Y3+  Yb3+ at pH=1.5 for all the studied sample compositions. It was experimentally shown that the doping of sorbents based on titanium (IV) oxyhydroxophosphates with zirconium (IV) cations, which differs from titanium (IV) in acid-base properties, leads to an increase in the sorption properties of ion exchangers, which allows the use of modified compositions for sorption of rare-earth metal cations from solutions with high acidity. It was established that partial dehydration of the sorption matrix and increase in temperature increase the sorption ability of ion-exchange materials. Sorption extraction of rare-earth element cations by sorbents of various compositions was carried out from solutions simulating real technological objects generated during the processing of nuclear fuel waste. It is shown that sorption materials based on hydrated titanium (IV) oxohydroxophosphates are promising ion exchangers for the extraction of rare-earth element cations from technological solutions with complex chemical composition. It was established that unmodified sorbent compositions are promising for the selective extraction of rare-earth element cations, while modified compositions are of interest for group sorption. The thermal treatment of a sorbent saturated with radioisotopes leads to the formation of crystalline insoluble mineral-like compounds, which ensures reliable immobilization of the sorbed components during long-term storage of the spent product.

Effect of extra-framework cation in ion-exchanged ZSM-5 from rice husk ash on CO2 adsorption

ZSM-5 zeolite with high aluminum content (Si/Al = 25) was synthesized and then cation-exchanged with alkali metal, alkaline earth metal, transition metal and rare earth metal cations (Li+, Mg2+, Ca2+, Cu2+, Zn2+, La3+ and Ce3+). Crystal structure and physicochemical properties were characterized by XRD, FTIR, TGA/DTG, XRF and nitrogen adsorption-desorption measurement. CO2 adsorption isotherms of all samples were recorded approximately 0–120 kPa at 0 °C, 30 °C and 60 °C, and they were all successfully fitted by the Toth model. The N2 adsorption isotherm presented an approximate straight rising line, and it was perfectly fitted by the Langmuir model. In addition, the CO2/N2 adsorption selectivity, Henry's law constant and the working adsorption quantity were calculated by single component CO2 and N2 adsorption testing. Transition metal cations Cu2+ and Zn2+ type ZSM-5 had the maximum adsorption quantity of 0 °C (70.24 and 74.38 cm3/g), and they had the maximum adsorption selectivity under high pressure and adsorption saturation conditions. The adsorption heat of all ion-exchanged samples was lower than Na-ZSM-5, and it had the approximate value at high loadings (in the range of 15.46–17.65 kJ/mol).

Die monoklinen Seltenerdmetall(III)-Chlorid-Oxidoarsenate(III) mit der Zusammensetzung SE 5Cl3[AsO3]4 (SE=La–Nd, Sm)

Abstract The rare earth metal(III) chloride oxidoarsenates(III) with the composition RE 5Cl3[AsO3]4 (RE = La–Nd, Sm) could be synthesized via solid-state methods through the reaction of arsenic sesquioxide (As2O3) with the corresponding rare earth metal compounds (La2O3, CeO2 + metallic Ce, Pr6O11, Nd2O3 or metallic Sm) using several chloride-containing fluxing agents in evacuated silica glass ampoules. The compounds build up non-isotypic crystal structures in the monoclinic space groups C2/c for RE = La–Pr, and P2/c for RE = Nd and Sm. All rare earth metal(III) cations exhibit coordination numbers of eight. While (RE1)3+ and (RE2)3+ are only surrounded by oxygen atoms in the form of distorted square antiprisms or prisms, (RE3)3+ is coordinated square antiprismatically by four oxygen atoms and four chloride anions. Although the coordination polyhedra in both structures differ only marginally, their connection patterns show more pronounced differences. This regards especially the (RE)3+ cations and results from different site symmetries of the (Cl1)− anions. All As3+ lone-pair cations are coordinated by three oxygen atoms to form ψ1-tetrahedral [AsO3]3− complex anions with their non-binding (lone) electron pairs pointing into empty channels along [010].

The rare earth metal hydride tellurides REHTe (RE=Y, La–Nd, Gd–Er)

Abstract The synthesis and crystal structure of a series of rare earth metal hydride tellurides with the composition REHTe (RE = Y, La–Nd, Gd–Er) is reported. These compounds have been obtained by the reaction of rare earth metal dihydrides (REH2) with elemental tellurium in sealed tantalum capsules at T = 700°C using cesium chloride (CsCl) as fluxing agent, which can be washed away with water due to the astonishing insensitivity of these hydride tellurides (REHTe) against hydrolysis. All of the compounds crystallize in the hexagonal space group P6̅m2 with a filled WC-type crystal structure, exhibiting a mutual trigonal-prismatic coordination of the heavy ions (RE 3+ and Te2−), while the hydride anions reside in the trigonal prismatic voids surrounded by three rare earth metal cations expanding their coordination pattern to a tricapped trigonal prism. This 1H-type crystal structure is compared with the 1H- and 2H-type structures of the respective hydride selenides (REHSe, RE = Y, La–Nd, Gd–Tm, Lu). Both hexagonal basic crystal structures can be derived from the AlB2-type structure as demonstrated in a Bärnighausen tree by group-subgroup relationships.

An investigation of the binding of (S)-monothioBINOLate to rare earth metal cations

Two novel rare earth compounds have been synthesized using the previously reported (S)-MonoThioBINOL [(S)-H2-MTB], (S)-2-hydroxy-2′-mercapto-1,1′-binaphthyl). We have shown here that while the H-bonded complex containing TMG-H+ (tetramethyl guanidium cation) maintains the structure that the analogous BINOLate complex adopts, the complex with lithium cations in the secondary coordination sphere crystallizes as an ‘–ate’ complex with an outer sphere lithium counter cation solvated by DME.