Search Results (152)

The reaction of nitronyl nitroxide biradical NITPhMeImbis(5-(2-methylimidazole)-1,3-bis(1′-oxyl-3′-oxido-4′,4′,5′,5′-tetramethyl-4,5-hydro-1H-imidazol-2-yl)-benzene) with Dy(hfac)₃ and La(hfac)₃ (hfac = hexafluoroacetylacetonate) afforded a heterolanthanide complex [Dy_0.56La_1.44(hfac)₇(NITPhMeImbisH)] (1). In this complex, the biradical NITPhMeImbis ligand chelates one Ln(III) ion via its two neighboring NO units and simultaneously binds the La(III) ion through another NO group to form a dinuclear structure. Direct current (dc) magnetic measurement shows the dominant ferromagnetic couplings in Complex 1. Spin dynamics studies exhibit visible frequency-dependent peaks of χ″ signals under a dc field evidenced by field-induced magnetic relaxation behavior, which is a combination of Orbach and QTM processes, giving the U_eff, τ₀ and τ_QTM values of 15.14 K, 3.04 × 10⁻⁷ s and 3.61 × 10⁻⁴ s, respectively. Full article

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

Three new asymmetrically coordinated lanthanide derivatives based on the bicompartmental salen-type ligands N,N′-bis(3-ethoxysalicylidene)propylene-1,3-diamine (H₂EtOsalpr) and 3-ethoxysalicylaldehyde (HEtvain) have been synthesized and structurally and photophysically characterized. All the compounds show dimeric structures of the general formula [Ln(H₂EtOsalpr)(NO₃)₂(Etvain)]₂ (Ln = Nd, Eu, Dy), with each salen-type ligand bridging two lanthanide ions. The Etvain ligand comes from the H₂EtOsalpr decomposition being coordinated to the corresponding lanthanide. The Nd(III) derivative shows fluorescence emission in the NIR region, but for the Eu(III) and Dy(III) compounds, only a broad band, attributed to the ligand emission, was observed. Full article

Four similar dinuclear lanthanide complexes have been synthesized by linking two [Ln(hfac)_2–3] units (hfac stands for hexafluoroacetylacetone) with different μ-O bridging ligands. The 2,2′-bipyridine-N-oxide ligand (bmpo) constructed two centrosymmetric complexes [Ln₂(hfac)₆(bmpo)₂] (Ln = Dy(1), Tb(2)), with nine-coordinated Ln^III ions showing C_s low symmetry, while the ligand di(2-pyridyl)methanediol (py₂C(OH)₂) formed another two compounds [Ln₂(hfac)₄(py₂C(OH)O)₂] (Ln = Dy(3), Tb(4)), with two kinds of eight-coordinated Ln^III ions exhibiting improved symmetries of D_4d and D_2d. Magnetic analysis reveals that Dy₂ complex 1 shows intramolecular antiferromagnetic coupling (J = −1.07 cm⁻¹) and no relaxation process above 2.0 K even in a 1000 Oe dc field, owing to the low symmetry of Dy^III ions, while the similar Dy₂ complex 3 with improved Dy^III symmetry shows ferromagnetic coupling (J = 1.17 cm⁻¹), which induces a 1000 Oe dc field-induced two-step magnetization relaxation processes with effective energy barrier U_eff = 47.4 K and 25.2 K for the slow relaxation and fast relaxation processes, respectively. This study proves again that the improved symmetry combined with intramolecular ferromagnetic interactions, both mediated by bridging ligands, can enhance the Dy^III anisotropy, further quench the quantum tunneling of the magnetization, and finally, enhance the magnetic behavior of Ln^III-based systems. Full article

The design, synthesis, and study of lanthanide coordination compounds with luminescent and magnetic properties attractive in modern technologies is still a pressing and challenging task. In the present work, a series of coordination compounds of tetrakis-carbacylamidophosphate PPh₄[LnL₄] (where HL = diphenyl-N-benzoylamidophosphate) with several lanthanide ions such as Nd^III, Sm^III, Dy^III, and Tm^III was prepared and studied by X-ray analysis and luminescence spectroscopy at 293 and 77 K, as well as by magnetic measurements. Coordination compounds are not isostructural, but the type of coordination is the same. All of them have intense sensitized emission. PPh₄[SmL₄], PPh₄[DyL₄], and PPh₄[TmL₄] chelates are characterized by dual visible and infrared emission and mechanoluminescence. In addition, PPh₄[DyL₄] has multifunctional properties such as Vis and NIR emissions, brilliant mechanoluminescence and single-ion molecular magnet (SIM) properties. This type of compound holds great promise in multifunctional magnetic radiation converters. Full article

Multifunctional materials bearing photoluminescence, single-molecule magnet (SMM) behavior, and proton conduction have been particularly attractive for various promising applications in optics, molecular spintronics, high-density data storage, and fuel cells. However, these kinds of multifunctional systems have rarely been reported. Herein, a Dy^III-SMM together with luminescent and proton-conducting properties, [Dy₂(1-tza)₄(phen)₄]∙(ClO₄)₂∙(H₂O)₂ (1, 1-tza = 2-(1H-tetrazol-1-yl)acetic, phen = 1,10-phenanthroline), was prepared and structurally characterized. Complex 1 features a dinuclear structure bridged by carboxylate oxygen atoms of the 1-tza⁻ ligands, and its supramolecular network contains a 1D stacking channel. Complex 1 exhibits strong room-temperature Dy^III characteristic emissions and SMM behaviors. In addition, complex 1 shows a moderate proton conductivity with 4.00 × 10⁻⁶ S cm⁻¹ at 37 °C and 100% R.H. (R.H. = Relative Humidity), which may be ascribed to the 1D-extended H-bonds in the 1D stacking channel of 1. 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

The monoclinic rare-earth metal(III) bromide oxoarsenates(III) RE₅Br₃[AsO₃]₄ of the A-type (RE = La and Ce) crystallize in the space group C2/c with the lattice parameters a = 1834.67(9) pm, b = 553.41(3) pm, c = 1732.16(9) pm and β = 107.380(3)° for La₅Br₃[AsO₃]₄ and a = 1827.82(9) pm, b = 550.67(3) pm, c = 1714.23(9) pm and β = 107.372(3)° for Ce₅Br₃[AsO₃]₄ with Z = 4, while, for the B-type (RE = Pr, Nd and Sm–Tb), they prefer the space group P2/c with lattice parameters from a = 881.23(5) pm, b = 547.32(3) pm, c = 1701.14(9) pm and β = 90.231(3)° for Pr₅Br₃[AsO₃]₄ to a = 875.71(5) pm, b = 535.90(3) pm, c = 1643.04(9) pm and β = 90.052(3)° for Tb₅Br₃[AsO₃]₄ with Z = 2. The closely related rare-earth metal(III) bromide oxoarsenates(III) RE₃Br₂[AsO₃][As₂O₅] crystallize in the triclinic space group P$\overline{1}$ with lattice parameters from a = 539.15(4) pm, b = 870.68(6) pm, c = 1092.34(8), α = 90.661(2)°, β = 94. 792(2)° and γ = 90.223(2)° for Dy₃Br₂[AsO₃][As₂O₅] to a = 533.56(4) pm, b = 869.61(6) pm, c = 1076.70(8), α = 90.698(2)°, β = 94.785(2)° and γ = 90.053(2)° for Yb₃Br₂[AsO₃][As₂O₅] with Z = 2. All three structures have the same building units with [REO₈]¹³⁻ and [REO₄Br₄]⁹⁻ polyhedra as well as isolated ψ¹-tetrahedral [AsO₃]³⁻ anions in common, with the exception that, in the latter two, ψ¹-[AsO₃]³⁻ tetrahedra linked by a corner form a pyroanionic [As₂O₅]⁴⁻ entity. A- and B-type differ in the stacking sequence of their $\begin{array}{c}2\\ \infty \end{array}${[(RE3)O$\begin{array}{c}t\\ 4/1\end{array}$(Br1)$\begin{array}{c}v\\ 1/2\end{array}$(Br2)$\begin{array}{c}e\\ 3/3\end{array}$]^6.5−} layers. While the former have an ABC sequence, the latter exhibit an AAA variant. In the triclinic structures, the (RE3)³⁺ sites are thinned out, while the As³⁺ sites are simultaneously enriched, resulting in the mentioned condensed units. Full article

Cryogenic magnetic refrigerants based on the magnetocaloric effect (MCE) hold significant potential as substitutes for the expensive and scarce He-3. Gd(III)-based complexes are considered excellent candidates for low-temperature magnetic refrigerants. We have synthesized a series of Ln(III)-based metal-organic framework (MOF) Ln-3D (Ln = Gd/Dy) by the slow release of oxalates in situ from organic ligands (disodium edetate dehydrate (EDTA-2Na) and thiodiglycolic acid). Structural analysis shows that the Ln-3D is a neutral 3D framework with one-dimensional channels connected by [Ln(H₂O)₃]³⁺ as nodes and C₂O₄²⁻ as linkers. Magnetic measurements show that Gd-3D exhibits very weak antiferromagnetic interactions with a maximum −ΔS_m value of 36.6 J kg⁻¹ K⁻¹ (−ΔS_v = 74.47 mJ cm⁻³ K⁻¹) at 2 K and 7 T. The −ΔS_m value is 28.4 J kg⁻¹ K⁻¹ at 2 K and 3 T, which is much larger than that of commercial Gd₃Ga₅O₁₂ (GGG), indicating its potential as a low-temperature magnetic refrigerant. Full article

Herein, we present the synthesis and structural characterisation of two layered MOFs with the asymmetric ligand 3-chloro,6-cyano-2,5-dihydroxy-1,4-benzoquinone dianion (C₆O₄(CN)Cl²⁻ = chlorocyananilato). These compounds, formulated as (H₃O)[Eu(C₆O₄(CN)Cl)₂(H₂O)]·34H₂O (1) and (H₃O)[Dy(C₆O₄(CN)Cl)₂(H₂O)]·44H₂O (2), are isostructural and show a (4,4)-layered square structure with the crystallisation water molecules located between the layers. The lanthanoid ions are surrounded by four bis-bidentate chlorocyananilato ligands that connect each Ln^III centre with other four, giving rise to square cavities formed by Ln^III centres in the vertices and chlorocyananilato ligands as the sides. There is an additional coordinated water molecule that occupies the caped position of the capped square antiprismatic coordination geometry around the Ln^III centres. The magnetic properties show the presence of a field-induced slow relaxation of the magnetisation in the Dy^III derivative at low temperatures that follows Direct and Orbach relaxation mechanisms with an energy barrier of 36(3) K. 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

In this work, we describe the synthesis, crystal structures and magnetic properties of four air-stable mononuclear lanthanide(III) complexes with the N-(2,4,6-trimethylphenyl)oxamate (Htmpa) of formula: n-Bu₄N[Nd(Htmpa)₄(H₂O)]·4H₂O (1), n-Bu₄N[Gd(Htmpa)₄(H₂O)]·3DMSO·2H₂O (2), n-Bu₄N[Tb(Htmpa)₄(H₂O)]·3DMSO·1H₂O (3) and n-Bu₄N[Dy(Htmpa)₄(H₂O)]·3DMSO·2H₂O (4) (n-Bu₄N⁺ = n-tetrabutylammonium; DMSO = dimethylsulfoxide). Their crystal structures reveal the occurrence of calixarene-type monoanionic species containing all-cis-disposed Htmpa ligands and one water molecule coordinated with the respective Ln^III ion (Ln = Nd, Gd, Tb and Dy), featuring a nine-coordinated environment with muffin (MFF-9) (1) or spherical-capped square antiprism (CSAPR-9) (2–4) geometry. The major difference between their crystal structures is related to the nature of crystallization solvent molecules, either water (1) or both DMSO and water (2–4). The intermolecular hydrogen bonds among the self-complementary Htmpa ligands in all four compounds mediated a 2 D supramolecular network in the solid state. Direct-current (dc) magnetic properties for 1–4 show typical behavior for the ground state terms of the Ln^III ions [⁴I_9/2 (Nd); ⁸S_7/2(Gd), ⁷F₆ (Tb), ⁶H^15/2 (Dy)]. Alternating-current (ac) magnetic measurements reveal the presence of slow magnetic relaxation without the presence of a dc field only for 4. In contrast, field-induced slow magnetic relaxation behavior was found in complexes 1, 2 and 3. Full article

We report the research results of polynuclear complexes consisting of 3d-4f mixed-metal cores that are maintained by acetate ligands and multidentate Schiff base ligands with structurally exposed thioether groups. The presence of the latter at the periphery of these neutral compounds enables their anchoring onto substrate surfaces. Specifically, we investigated the electronic and magnetic properties as well as the structural arrangement in {Mn^II₃Mn^IVLn^III₃} with Ln = Dy, Yb coordination complexes using various complementary methods. We studied the electronic and atomic structure of the target compounds using the XAS and XES techniques. The molecular structures of the compounds were determined using density functional theory, and the magnetic data were obtained as a function of the magnetic field. Using the XMCD method, we followed the changes in the electronic and magnetic properties of adsorbed magnetic compounds induced by the reaction of ligands through interaction with the substrate. The complexes show antiferromagnetic exchange interactions between Mn and Ln ions. The spectroscopic analyses confirmed the structural and electronic integrity of complexes in organic solution. This study provides important input for a full understanding of the dependence of the magnetic properties and the molecule–substrate interaction of single adsorbed molecules on the type of ligands. It highlights the importance of chemical synthesis for controlling and tailoring the magnetic properties of metalorganic molecules for their use as optimized building blocks of future molecular spin electronics. 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

A Dy(III) coordination polymer (CP), [Dy(spasds)(H₂O)₂]_n (1) (Na₂Hspasds = 5-(4-sulfophenylazo)salicylic disodium salt), has been synthesized using a hydrothermal method and characterized. 1 features a 2D layered structure, where the spasda³⁻ anions act as pentadentate ligands, adopting carboxylate, sulfonate and phenolate groups to bridge with four Dy centers in η₃-μ¹: μ², η₂-μ¹: μ¹, and monodentate coordination modes, respectively. It possesses a unique (4,4)-connected net with a Schläfli symbol of {4⁴·6²}{4}₂. The luminescence study revealed that 1 exhibited a broad fluorescent emission band at 392 nm. Moreover, the visual blue color has been confirmed by the CIE plot. 1 can serve as a dual-functional luminescent sensor toward Fe³⁺ and MnO₄⁻ through the luminescence quenching effect, with limits of detection (LODs) of 9.30 × 10⁻⁷ and 1.19 × 10⁻⁶ M, respectively. The LODs are relatively low in comparison with those of the reported CP-based sensors for Fe³⁺ and MnO₄⁻. In addition, 1 also has high selectivity and remarkable anti-interference ability, as well as good recyclability for at least five cycles. Furthermore, the potential application of the sensor for the detection of Fe³⁺ and MnO₄⁻ was studied through simulated wastewater samples with different concentrations. The possible sensing mechanisms were investigated using Ultraviolet-Visible (UV-Vis) absorption spectroscopy and density functional theory (DFT) calculations. The results revealed that the luminescence turn-off effects toward Fe³⁺ and MnO₄⁻ were caused by competitive absorption and photoinduced electron transfer (PET), and competitive absorption and inner filter effect (IFE), respectively. Full article