Search Results (41)

Herein, we present the synthesis and characterization of a series of isostructural lanthanide(III) compounds with the N-(4-carboxyphenyl)oxamic acid (H₃pcpa) ligand of the general formula as {[Ln₂(Hpcpa)₃(H₂O)₅]}_n [Ln = Dy(III) 1, Ho(III) 2, Er(III) 3]. The structure of 3 consists of neutral zig–zag chains of Er(III) ions, with Hpcpa^2– ligands acting as bridges in a bidentate/monodentate coordination mode with five water molecules achieving the eight-coordination around the two Er(III) ions within the repeating bis(carboxylate)-bridged dinuclear units along the chain. The magnetic and magnetocaloric properties were studied for 1–3. Compound 1 presents a field-induced slow relaxation of the magnetization with a “reciprocating thermal behavior” below 5 K for H = 0.25 T, while 2 shows maxima of the magnetic entropy from 3 up to 6 K for ΔH > 2 T. Full article

In this paper, we investigate the magnetic exchange interaction and magnetization dynamics of two new members of the [LnRad(NO₃)₃] family, where Rad is a tripodal nitroxide, and Ln is Er(III) or Yb(III), having the prolate type electron density. Single OK crystal and powder X-ray diffraction studies showed that these complexes are isostructural with their previously investigated Y, Gd, Dy, Tm, Tb, Eu, and Lu congeners. A magnetometric investigation, supported by ab initio calculations, showed the presence of antiferromagnetic coupling between the lanthanide ion and the radical in both compounds with estimated J values of ≈7 and ≈20 cm⁻¹ for Er and Yb, respectively (+J S_eff∙ S formalism). Full article

This work presents a comparative study of five rare earth compounds—Erbium nitrate pentahydrate lll (Er), Neodymium nitrate pentahydrate (Nd), Samarium III Nitrate Hexahydrate (Sm), Yterbium III Chloride Hexahydrate (Yb) and Praseodymium nitrate hexahydrate lll (Pr)—protecting API 5L X70 steel from corrosion in saline medium that uses electrochemical impedance spectroscopy (EIS) and polarization curves (CPs) at different concentrations and in static mode. The results show that Erbium is the best corrosion inhibitor, containing 50 ppm and reaching an inhibition efficiency of about 89%, and similar result was shown by Sm with an IE~87.9%, while the other rare earths (Nd, Yb and Pr) showed a decrease in corrosion protection at the same concentration, since they were below an IE~80%. On the other hand, with the Langmuir model it was possible to describe that the adsorption process of the three rare earths follows a combined physisorption–chemisorption process to protect the metal’s surface. The observed adsorption free energy, ΔG°ads, reaches −38.7 kJ/mol for Er, −34.4 kJ/mol for Nd, and −33.6 kJ/mol for Pr; whereas Sm and Yb have adsorption free energies of −33.9 and −35.0 kJ/mol, respectively. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) further confirmed the formation of a protective film. Their characterization using density functional theory showed the transference of charge from the iron cluster towards the rare earth metal compounds. The adsorption process produced a slightly polarized region of interaction with the metal surface. Also, it was found that the adsorption of the rare earths affected the magnetic properties of the surface of the iron cluster. Quantum chemical descriptors, such as Pearson’s HSAB (Hard and Soft Acids and Bases) descriptors, were useful in predicting the behavior of the flow of electrons between the metal surface and the interacting rare earth ions. Full article

We report here the synthesis of a series of nine coordinated mononuclear Ln^III complexes [LnL₁Cl₂(DMF)]Cl·2.5DMF and [LnL¹(L₂)₂]Cl·4CH₃OH (Ln^III = Gd^III, Dy^III, Er^III and Yb^III, HL₂ = 9-anthracenecarboxylic acid), where L1 is a hexadentate N₄O₂ Schiff base ligand prepared from the condensation of 1,10-phenanthroline-2,9-dicarbaldehyde and semicarbazone. The X-ray crystal structures of these complexes show the Ln^III ions to possess LnN₄O₂Cl₂ and LnN₄O₄ coordination spheres, which can be considered to be derived from a hexagonal bipyramidal geometry, with the ligand in the equatorial plane and the anions (chloride or 9-antracenecarboxylate) in axial positions, which undergo distortion after coordination of either a molecule of DMF or a bidentate coordination of the 9-anthracenecarboxxylate ligand. All these compounds exhibit field-induced slow magnetization relaxation (SMR). The absence of SMR at zero field due to QTM, as well as the processes involved in the magnetic relaxation under a field of 0.1 T, have been justified on the basis of theoretical calculations and the distortion of the respective coordination spheres. The severe discrepancy between the calculated and experimental thermal energy barriers for the Dy^III complexes seems to indicate that the relaxation occurs with the contribution of spin–vibrational coupling, which is favored by the flexibility of the ligand. Full article

By combining Er^III and Yb^III ions with 3,6-dithiophene-anilate (Th₂An) and scorpionate hydrotris(pyrazol-1-yl)borate (HBpz₃⁻) ligands new luminescent dinuclear complexes are obtained. The two materials formulated as [((HB(pz)₃)₂Yb)₂(μ-th₂An)]·4DCM·1.3H₂O 1Yb and [((HB(pz)₃)₂Er)₂(μ-th₂An)]·4DCM·1.8H₂O 1Er, respectively, have been structurally characterized by SC-XRD and PXRD studies. This study presents a comprehensive investigation of the photophysical properties of the Th₂An ligand for the first time. Our findings reveal the crucial role of the thiophene anilate as an effective optical antenna, which sensitizes near-infrared (NIR)-emitting lanthanide ions, specifically Er^III and Yb^III. The significant impact of vibrational quenching on the Ln^III NIR emission efficiency has been also highlighted. Full article

4-Acylpyrazolones are important ligands in analytical chemistry and technologies used for the separation and concentration of various metals. We have proposed a novel method for obtaining a material that consists of covalently immobilized functionalized ionic liquid on the surface of a mineral carrier featuring a coordination-active fragment of 4-acylpyrazolone. For its synthesis, we have introduced a strategy based on the quaternization of surface azolyl groups from 3-(1H-imidazol-1-yl)propyl silica with an alkylating reagent containing a 4-acylpyrazolone motif-4-(6-bromohexanoyl)-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one. This method of covalent immobilization preserves the 1,3-dioxo fragment, which ensures the effective binding of metal ions. The success of this functionalization has been confirmed by IR and ¹³C NMR spectroscopy data, as well as by thermogravimetric analysis. The overall functional capacity was found to be 0.3 mmol/g. The potential of the synthesized organomineral material to concentrate five rare earth elements (REEs) representing the cerium (Eu(III), Sm(III)) and yttrium groups (Gd(III), Dy(III), Er(III)) has been demonstrated. It was shown that during extraction from multicomponent systems, both under static and dynamic preconcentration conditions, there is a competitive influence of analytes, and their separation can be evaluated under dynamic conditions based on dynamic output curves and calculated distribution coefficients. It was shown that for systems where Kd > 1.8, quantitative separation can be performed in a dynamic mode of sorption under selected conditions. Full article

Seven new lanthanide coordination polymers, namely [Ln(cpt)₃H₂O)]n(Ln = La (1), Pr (2), Sm (3), Eu (4), Gd (5), Dy (6), and Er (7)), which were synthesized under hydrothermal conditions using 4′-(4-(4-carboxyphenyloxy)phenyl)-4,2′:6′,4′-tripyridine (Hcpt) as the ligand. The crystal structures of these seven complexes were determined using single-crystal X-ray diffraction, and they were found to be isostructural, crystallizing in the triclinic P$\stackrel{-}{1}$ space group. The Ln(III) ions were nine-coordinated with tricapped trigonal prism coordination geometry. The Ln(III) cations were coordinated by carboxylic and pyridine groups from (cpt)⁻ ligands, forming one-dimensional ring-chain structures. Furthermore, the luminescent properties of complexes 1–7 were investigated using fluorescent spectra in the solid state. The fluorescence sensing experiments demonstrated that complex 4 exhibits high selectivity and sensitivity for detecting Co²⁺, Cu²⁺ ions, and nitrobenzene. Moreover, complex 3 shows good capability for detecting Cu²⁺ ions and nitrobenzene. Additionally, the sensing mechanism was also thoroughly examined through theoretical calculations. Full article

The removal of low concentrations of rare-earth ions (e.g., Er(III)) from water has stimulated interest in the field of mineral processing and water treatment. Here, an ion-exchange and complexation-assisted precipitation method for the removal of low concentrations of Er(III) from water using heptadecyl-1,1-bisphosphonic acid (HBPA) was investigated. The results showed that effective cation-exchange between Er(III) ions and the bisphosphonate headgroup was achieved, and the solution pH abruptly decreased from 6.5 to around 3.1 at the first stage, which further led to the formation of less soluble Er(III) heptadecyl-1,1-bisphosphonate complexes. While low concentrations of Er(III) ions in water are typically treated by the addition of HBPA, followed by the addition of sodium bicarbonate (adjusting the pH to 6–8) and activate carbon, Er(III) ions could be efficiently removed from aqueous solution after about 30 min based on the cation-exchange and complexation-assisted precipitation method. Additionally, the removal of ultra trace amounts of Er(III) ions was not significantly affected by coexisting trace amounts of alkaline-earth metal ions (Mg²⁺, Ca²⁺ and Sr²⁺). HBPA is an effective Er(III) chelator, which may be a potential and promising alternative technique to remove Er(III) ions from aqueous solutions. Full article

The broad emission bump in the electromagnetic spectra observed following the detection of gravitational waves created during the kilonova event of the merging of two neutron stars in August 2017, named GW170817, has been linked to the heavy elements of lanthanides (Z = 57–71) and a new understanding of the creation of heavy elements in the r-process. The initial spectral emission bump has a wavelength range of 3000–7000 Å, thus covering the region of ultraviolet (UV) to optical (O) wavelengths, and is similar to those seen for lanthanides. Most lanthanides have a large number of closely lying energy levels, which introduce extensive sets of radiative transitions that often form broad regions of lines of significant strength. The current study explores these broad features through the photoabsorption spectroscopy of 25 lanthanide ions, Ho I-III, Er I-IV, Tm I-V, Yb I-VI, and Lu I-VII. With excitation only to a few orbitals beyond the ground configurations, we find that most of these ions cover a large number of bound levels with open $4f$ orbitals and produce tens to hundreds of thousands of lines that may form one or multiple broad features in the X-ray to UV, O, and infrared (IR) regions. The spectra of 25 ions are presented, indicating the presence, shapes, and wavelength regions of these features. The accuracy of the atomic data used to interpret the merger spectra is an ongoing problem. The present study aims at providing improved atomic data for the energies and transition parameters obtained using relativistic Breit–Pauli approximation implemented in the atomic structure code SUPERSTRUCTURE and predicting possible features. The present data have been benchmarked with available experimental data for the energies, transition parameters, and Ho II spectrum. The study finds that a number of ions under the present study are possible contributors to the emission bump of GW170817. All atomic data will be made available online in the NORAD-Atomic-Data database. Full article

Three new cationic complexes, [Cu₄Tb₂(H₂L)₄(NO₃)₄(H₂O)₃](NO₃)₂·5.5H₂O·2MeOH (1), [Cu₄Ho₂(H₂L)₄(NO₃)₄(H₂O)₃](NO₃)₂·7.5H₂O (2), and [Cu₄Er₂(H₂ L)₄(NO₃)₄(H₂O)₃](NO₃)₂·7H₂O·3MeOH (3), were synthesized and studied using elemental and TG/DTG/DSC analyses, single-crystal X-ray diffraction, and magnetic measurements. The structure analysis showed that 1–3 crystallize as (NO₃)-bridged compounds and that the lanthanide(III) ion acts as a joint connecting two [CuH₂L] coordination units. In each heterotrinuclear unit, an asymmetry in the degree of planarity of the bridging CuO₂Ln fragments is observed. The Cu^II ions are five- and six-coordinate, with distorted square pyramidal and octahedral geometry, respectively, whereas the Ln^III ions are nine-coordinate. The solvates 1–3 are stable at room temperature, and their desolvation process is consistent with the loss of water and/or methanol molecules. The temperature dependence of the magnetic susceptibility and the field-dependent magnetization indicate the weak ferromagnetic interaction between the paramagnetic centers Cu^II and Tb^III/Ho^III 1 and 2. Full article

We successfully synthesized millimeter-sized single crystals of the molecular erbium(III) complex Er(acac)₃(cphen), where acac = acetylacetonate and cphen = 5-chloro-1,10-phenanthroline. The novelty of this work stems from the exhaustive examination of the polar and electronic properties of the obtained samples at the macro-, micro-, and nanoscale levels. The single crystal X-ray diffraction method demonstrates the monoclinic (noncentrosymmetric space group P2₁) crystallographic structure of the synthesized samples and scanning electron microscopy exhibits the terrace–ledge morphology of the surface in erbium(III) crystals. By using the piezoelectric force microscopy mode, the origin of the polar properties and the hyperpolarizability in the synthesized samples were assigned to the internal domain structure framed by the characteristic terrace–ledge topography. The direct piezoelectric coefficient (~d33) was found to be intensely dependent on the local area and was measured in the range of 4–8 pm/V. A nanoscale study using the kelvin probe force and capacitance force (dC/dz) microscopy modes exposed the effect of the Er ions clustering in the erbium(III) complex. The PFM method applied solely to the Er ion revealed the corresponding direct piezoelectric coefficient (~d33) of about 4 pm/V. Given the maximum piezoelectric coefficient in the erbium(III) complex at 8 pm/V, we highlight the significant importance of the spatial coordination between the lanthanide ion and the ligands. The polar coordination between the lanthanide ion and the nitrogen and oxygen atoms was also corroborated by Raman spectroscopy supported by the density functional theory calculations. The obtained results can be of paramount importance for the application of molecular erbium(III) complex crystals in low-magnitude magnetic or electric field devices, which would reduce the energy consumption and speed up the processing switching in nonvolatile memory devices. Full article

A series of novel 3D coordination polymers [Ln₂(Qdca)₃(H₂O)_x]·yH₂O (x = 3 or 4, y = 0–4) assembled from selected lanthanide ions (Ln(III) = Nd, Eu, Tb, and Er) and a non-explored quinoline-2,4-dicarboxylate building block (Qdca²⁻ = C₁₁H₅NO₄²⁻) were prepared under hydrothermal conditions at temperatures of 100, 120, and 150 °C. Generally, an increase in synthesis temperature resulted in structural transformations and the formation of more hydrated compounds. The metal complexes were characterized by elemental analysis, single-crystal and powder X-ray diffraction methods, thermal analysis (TG-DSC), ATR/FTIR, UV/Vis, and luminescence spectroscopy. The structural variety of three-dimensional coordination polymers can be ascribed to the temperature effect, which enforces the diversity of quinoline-2,4-dicarboxylate ligand denticity and conformation. The Qdca²⁻ ligand only behaves as a bridging or bridging–chelating building block binding two to five metal centers with seven different coordination modes arising mainly from different carboxylate group coordination types. The presence of water molecules in the structures of complexes is crucial for their stability. The removal of both coordinated and non-coordinated water molecules leads to the disintegration and combustion of metal–organic frameworks to the appropriate lanthanide oxides. The luminescence features of complexes, quantum yield, and luminescent lifetimes were measured and analyzed. Only the Eu complexes show emission in the VIS region, whereas Nd and Er complexes emit in the NIR range. The luminescence properties of complexes were correlated with the crystal structures of the investigated complexes. Full article

The self-assembly reaction of the neutral dicyano-bis(1,10-phenanthroline) iron(II) complex with lanthanide ions (Ln = Eu(III), Gd(III), Er(III)) provided two different classes of heterometallic cyano-bridged 3d-4f architectures depending on the nature of the counteranion, irrespective of the size of the 4f metal ion. Tetranuclear oligomers with a squared Fe₂Ln₂ core were isolated when using nitrate salts, whereas unusual 1D polymeric chains were obtained when resorting to triflate salts under the same synthetic conditions. It is shown that the different structural motifs have a remarkable impact on the thermal stability and the optical properties of the compounds, which display a notable optical ipsochromism of the parent Fe(II) complex upon coordination with the Ln ion. This effect is significantly more pronounced in the polymeric chain than in the Fe₂Ln₂ oligomer both in solution and in the solid state. Structural evidence suggests that this behavior is likely related to the geometry of the CN-Ln bridge. On the other hand, more extended π-stacking interactions in the oligomer give rise to a broad charge-transfer absorption (600–1500 nm), making this compound promising as NIR absorber. Density Functional Theory calculations and electrochemical studies demonstrate that the observed negative chromism originates from the stabilization of a mixed metal/cyanide character HOMO with respect to a phenanthroline-centered LUMO. Full article

The property of persistent luminescence shows great potential for anti-counterfeiting technology and imaging by taking advantage of a background-free signal. Current anti-counterfeiting technologies face the challenge of low security and the inconvenience of being limited to visible light emission, as emitters in the NIR optical windows are required for such applications. Here, we report the preparation of a series of Zn_1+xGa_2−2xSn_xO₄ nanoparticles (ZGSO NPs) with persistent luminescence in the first and second near-infrared window to overcome these challenges. ZGSO NPs, doped with transition-metal (Cr³⁺ and/or Ni²⁺) and in some cases co-doped with rare-earth (Er³⁺) ions, were successfully prepared using an improved solid-state method with a subsequent milling process to reach sub-200 nm size particles. X-ray diffraction and absorption spectroscopy were used for the analysis of the structure and local crystal field around the dopant ions at different Sn⁴⁺/Ga³⁺ ratios. The size of the NPs was ~150 nm, measured by DLS. Doped ZGSO NPs exhibited intense photoluminescence in the range from red, NIR-I to NIR-II, and even NIR-III, under UV radiation, and showed persistent luminescence at 700 nm (NIR-I) and 1300 nm (NIR-II) after excitation removal. Hence, these NPs were evaluated for multi-level anti-counterfeiting technology. Full article

A series of 18 lanthanide-containing 1D-coordination polymers ¹_∞[Ln₂(2–PyPzH)₄Cl₆], Ln = La, Nd, Sm, dinuclear polymorphic complexes α–, β–[Ln₂(2–PyPzH)₄Cl₆], Ln = Sm, Eu, Gd, α–[Tb₂(2–PyPzH)₄Cl₆], and [Gd₂(2–PyPzH)₃(2–PyPz)Cl₅], mononuclear complexes [Ce(2–PyPzH)₃Cl₃], [Ln(2–PyPzH)₂Cl₃], Ln = Tb, Dy, Ho, and Er, and salt-like complexes [Gd₃(2–PyPzH)₈Cl₈]Cl and [PyH][Tb(2–PyPzH)₂Cl₄] were obtained from the reaction of the respective lanthanide chloride with the 3–(2–pyridyl)pyrazole (2–PyPzH) ligand at different temperatures. An antenna effect through ligand-to-metal energy transfer was observed for several products, leading to the highest luminescence efficiency displayed by a quantum yield of 92% in [Tb(2–PyPzH)₂Cl₃]. The Ce³⁺ ion in the complex [Ce(2–PyPzH)₃Cl₃] exhibits a bright and orange 5d-based broadband emission with a maximum at around 600 nm, marking an example of a strong reduction of the 5d-excited states of Ce(III). The absorption spectroscopy shows ion-specific 4f–4f transitions, which can be assigned to Nd³⁺, Sm³⁺, Eu³⁺, Dy³⁺, Ho³⁺, and Er³⁺ in a wide spectral range from UV–VIS to the NIR region. Full article