Lanthanide Nitrate Research Articles

The crystal structures of {LnCu5}3+ (Ln = Gd, Dy and Ho) 15-metallacrown-5 complexes and a reevaluation of the isotypic EuIII analogue.

Three new isotypic heteropolynuclear complexes, namely penta-aqua-carbonato-penta-kis-(glycinehydroxamato)nitrato-penta-copper(II)lanthanide(III) x-hydrate, [LnCu5(GlyHA)5(CO3)(NO3)(H2O)5]·xH2O (GlyHA2- is glycine-hydrox-amate, N-hy-droxy-glycinamidate or amino-aceto-hydroxamate, C2H4N2O2 2-), with lanthanide(III) (Ln III) = gadolinium (Gd, 1, x = 3.5), dysprosium (Dy, 2, x = 3.28) and holmium (Ho, 3, x = 3.445), within a 15-metallacrown-5 class were obtained on reaction of lanthanide(III) nitrate, copper(II) acetate and sodium glycinehydroxamate. Complexes 1-3 contain five copper(II) ions and five bridging GlyHA2- anions, forming a [CuGlyHA]5 metallamacrocyclic core. The Ln III ions are coordinated to the metallamacrocycle through five O-donor hydroxamates. The electroneutrality of complexes 1-3 is achieved by a bidentate carbonate anion coordinated to the Ln III ion and a monodentate nitrate anion coordinated apically to one of the copper(II) ions of the metallamacrocycle. The lattice parameters of complexes 1-3 are similar to those previously reported for an EuIII-CuII 15-metallacrown-5 complex with glycine-hydroxamate of proposed composition [EuCu5(GlyHA)5(OH)(NO3)2(H2O)4]·3.5H2O [Stemmler et al. (1999 ▸). Inorg. Chem. 38, 2807-2817]. High-quality X-ray data obtained for 1-3 have allowed a re-evaluation of the X-ray data solution proposed earlier for the EuCu5 complex and suggest that the formula is actually [EuCu5(GlyHA)5(CO3)(NO3)(H2O)5]·3.5H2O.

Simple Preparation of LaPO4:Ce, Tb Phosphors by an Ionic-Liquid-Driven Supported Liquid Membrane System.

In this work, LaPO4:Ce, Tb phosphors were prepared by firing a LaPO4:Ce, Tb precipitate using an ionic-liquid-driven supported liquid membrane system. The entire system consisted of three parts: a mixed rare earth ion supply phase, a phosphate supply phase, and an ionic-liquid-driven supporting liquid membrane phase. This method showed the advantages of a high flux, high efficiency, and more controllable reaction process. The release rate of PO43− from the liquid film under different types of ionic liquid, the ratio of the rare earth ions in the precursor mixture, and the structure, morphology, and photoluminescence properties of LaPO4:Ce, Tb were investigated by inductively coupled plasma-atomic emission spectroscopy, X-ray diffraction, Raman spectra, scanning electron microscopy, and photoluminescence emission spectra methods. The results showed that a pure phase of lanthanum orthophosphate with a monoclinic structure can be formed. Due to differences in the anions in the rare earth supply phase, the prepared phosphors showed micro-spherical (when using rare earth sulfate as the raw material) and nanoscale stone-shape (when using rare earth nitrate as the raw material) morphologies. Moreover, the phosphors prepared by this method had good luminescent properties, reaching a maximum emission intensity under 277 nm excitation with a predominant green emission at 543 nm which corresponded to the 5D4-7F5 transition of Tb3+.

Study of chemical states of lanthanoid nitrate in solution by electrospray ionization and fast atom bombardment mass spectrometry

Lanthanoids (Ln) are used in batteries, magnets and various industrial materials. Due to wide applications and few resources, efficient methods for the recovery of Lns are required. In this study, the soluble states of Ln in aqueous and organic phases were directly observed by electrospray ionization mass spectrometry (ESI-MS). We used La(NO3)3, Pr(NO3)3, and Tb(NO3)3 as representatives of Ln in our studies. When La(NO3)3, and Tb(NO3)3 was dissolved in water at pH 4.7, [La2(NO3)3(H2O)n]3+ (n = 0, 3) or [La2(NO3)(OH)2(H2O)m]+ (m = 9, 10), were observed. When La(NO3)3, Pr(NO3)3, and Tb(NO3)3 were dissolved at pH 1.8, [La2(NO3)3(H2O)n]3+ (n = 0, 3, 6, 9), [Pr2(NO3)(OH)2(H2O)7]3+, [Tb2(NO3)(OH)2(H2O)n]3+ (n = 6, 9, 12, 15, 18) were mainly observed. Particularly, in the Pr and Tb solutions, monomers generated were identified. By fast atom bombardment mass spectrometry (FAB-MS), monomer of Ln was not observed but dimer with glycerin was observed. This indicated that monomer was sufficiently hydrated to be ionized by FAB-MS. But dimer with glycerin was ionized due to less hydration by FAB-MS.On the other hand, when La, Pr, and Tb were extracted with TOPO in hexane solution at pH 1.8, [Ln(NO3)2-3TOPO]+, [Ln(NO3)2-4TOPO]+, and the monomers and dimers of TOPO (Ln = La, Pr, and Tb) were observed. This ESI-MS method could be useful for identifying chemical species in both aqueous and organic solutions.

Trinuclear Lanthanide Coordination Clusters: Single-Molecule-Magnet Behavior and Catalytic Activity in the Friedel-Crafts Alkylation Reaction.

A new multidentate ligand (H3 L) was synthesized by the condensation reaction of 4-tert-butyl-2,6-diformylphenol and 2-amino-4-nitrophenol. The reaction of the ligand with hydrated lanthanide nitrate produced two isostructural trinuclear coordination clusters: [DyLn3 L3 (DMF)3 (H2 O)2 ] ⋅ 3.8DMFLn=Dy (1) and Nd (2) (DMF=N, N-dimethylformamide). Single-crystal X-ray diffraction analysis revealed that there are three lanthanide ions arranged in an almost perfect linear fashion in both complexes. Magnetic studies show single-molecule-magnet (SMM) behavior in the Dy derivative with τ0 =1.7×10-6 s and a thermal energy barrier of 7.0 cm-1 . Both complexes were used as catalysts towards the Friedel-Crafts alkylation reaction of indole with different aldehydes with yields varying from 59-98 %. Complex 1 showed better catalytic efficiency than complex 2. This is the first report of using trinuclear lanthanide coordination clusters as catalysts for the Friedel-Crafts alkylation reaction.

Two Ce3+-Substituted Selenotungstates Regulated by N, N-Dimethylethanolamine and Dimethylamine Hydrochloride.

Two multi-Ce3+-substituted selenotungstates (STs), [HDMEA][H2N(CH3)2]4H3Na4[Ce2(H2O)6(DMEA)W4O9(α-SeW9O33)3]·26H2O (1) and [H2N(CH3)2]10H4Na10[Ce2W4O9(H2O)7(α-SeW9O33)3]2·63H2O (2), were prepared by the one-pot approach of sodium tungstate, sodium selenite, and lanthanide nitrate in an acidic water solution in the presence of N, N-dimethylethanolamine (DMEA) or dimethylamine hydrochloride (DMAHC). 1 was obained in the presence of DMEA, whereas 2 was synthesized in the presence of DMAHC. The trimeric polyoxoanion of 1 contains an unusual V-shaped [Se3W29O103]20- group embracing a prominent heterometal oxide fragment, [Ce2(H2O)6(DMEA)W2O5]8+, and the hexameric polyoxoanion of 2 is constructed from two equivalent trimeric [Ce2W4O9(H2O)7(SeW9O33)3]224- subunits through two -O-W-O-Ce-O- linkages. The most worthy of attention is that the polyoxoanion of 1 can be approximatively viewed as a half of the polyoxoanion of 2 because of the coordination and blocking effect of DMEA. The stability of 1 and 2 in different water pH values was studied by electrospray ionization mass spectroscopy (ESI-MS), and the results manifest that 1 and 2 are stable in pH = 3.5-7.5 and 3.5-7.0, respectively. The oxidation reactions of aromatic sulfides catalyzed by H2O2 were studied when 1 or 2 worked as a catalyst, and experimental results reveal that 1 or 2 can serve as available catalysts for the oxidation of aromatic sulfides under mild conditions.

CONDITIONS OF FORMATION AND PHYSICO-CHEMICAL CHARACTERISTICS OF LITHIUM COORDINATION NITRATES OF LANTANOIDES LI3[LN2(NO3)9]∙3H2O (LN–LA–ND)

Single-crystal samples were synthesized and a complex physicochemical characterization of the lithium coordination nitrates of the rare-earth elements of the cerium subgroup of the isostructural series Li3[Ln2(NO3)9]∙3H2O (Ln – La–Nd) was carried out in order to obtain reliable knowledge of the joint behavior of the constituent components and features of transformations in the systems of nitrate precursors during the formation with thermal activation (25–1000 oC) of multicomponent oxide REE-containing functional materials for various purposes with structure perovskite, garnet according to modern technologies with reproducible perfect stable properties. It has been revealed that the structure of this type of compounds is based on rare-earth oxygen polyhedra in one way or another connected in space. Ln3+ ions play a dominant role in the complexation process, showing high coordination numbers of 12. The individuality of Ln-complexes in coordination nitrates is manifested: in a limited set of Ln-polyhedra; in the tendency of the complexing ion to create around itself a symmetrically organized coordination sphere; that the complexes with different composition and stoichiometry may correspond to the same, although significantly distorted coordination polyhedra. Li+ cations in the structure formation of alkaline rare-earth nitrates can have a significant effect on the shape of Ln3+-polyhedra and on the spatial packing of their construction. The data obtained give a good reason to assume that the process of decomposition of crystalline alkaline rare-earth nitrates in technological objects during thermal activation begins with the breaking of alkaline metal-oxygen bonds. This fact is confirmed by the results of studies on the behavior of the above compounds in the range of 25–1000 °C by thermographic means. Thermograms of the samples are characterized by two, in addition to the initial state, temperature ranges of mass stabilization, corresponding to the formation of anhydrous complex nitrates and their thermolysis products at temperatures above 900 °C. The predominant phase of the final products is – LiLnO2.

A series of three isostructural 1D lanthanide coordination network based on 4,4′,4″-((benzene-1,3,5-triyltris(methylene))tris(oxy))tribenzoate ligand: Synthesis, crystal structure and photophysical properties

Three 1D-coordination networks namely {[Ln(L)(DMF)(H2O)]·DMF}n. represented as EuL, GdL and TbL were obtained using the synthetized 4,4′,4″-((benzene-1,3,5-triyltris(methylene))tris(oxy))tribenzoic acid (H3L) as a ligand and lanthanide nitrate salts (Ln(NO3)3) (Ln = EuIII, GdIII or TbIII). The reactions were carried out under solvothermal conditions using a mixture of DMF and H2O. Single crystal X-ray analyses revealed that all three compounds are isostructural crystalizing in the triclinic space group P1-. They show an interesting binodal connected one-dimensional structure, with a static crystal disorder due to the different spatial orientations of DMF molecules. The triplet state energy of the H3L ligand obtained from {[Gd(L)(DMF)(H2O)]·DMF}n lies energetically above the main emitting states of both EuIII and TbIII. The photophysical properties were investigated in terms of excitation, emission spectra and emission lifetime at three different temperatures. EuL and TbL exhibit characteristic emission bands of the EuIII and TbIII with emission lifetimes of 0.51 ms and 0.90 ms, respectively. The emission lifetime values of EuL and TbL remain practically constant in the temperature range from 77 to 300 K. Furthermore, it is mentioned a possible effect of a crystal disorder on the luminescence profile of EuIII in EuL.

Relations between Structural and Luminescence Properties of Novel Lanthanide Nitrate Complexes with Bis-phosphoramidate Ligands.

Five new bisphosphoramide-based LnIII nitrate complexes [La2(NO3)6L3I] n (1), [Ce2(NO3)6L3I] n (2), [Sm2(NO3)6L3II] n (3), Sm2(NO3)6L3III (4), and Er(NO3)3L2III (5) [LI = piperazine-1,4-diylbis(diphenyl phosphine oxide), LII = N, N'-(ethane-1,2-diyl)bis( N-methyl- P, P-diphenylphosphinic amide, and LIII = N, N'-(ethane-1,2-diyl)bis( P, P-diphenylphosphinic amide)] have been synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), and single crystal X-ray and powder diffractions. The results of the X-ray diffraction analysis revealed the new polymorph of LIII, and the structural diversity of the synthesized complexes in the solid state. Complexes 1-3 display two-dimensional coordination polymers (2D-CP), containing layers with honeycomb (6, 3) topology. In these 2D-CPs, each Ln center (La, Ce, and Sm in 1, 2, and 3, respectively) could be considered as a triconnected node, linked by three bridging bisphosphoramide ligands as two-connecting linkers. In contrast, 4 is a discrete binuclear complex, in which bidentate LIII ligand has two entirely different conformations: the syn chelating and the anti bridging. Cationic complex 5 shows the monomeric structure, where bidentate LIII adopts the syn-chelating conformation. A comprehensive luminescence investigation has been performed on free ligands and their corresponding complexes as well. The synthesized compounds display a variety of luminescence behavior, including the ligand-centered fluorescence in 1, 2, and 5, two distinct emission peaks in 1 and 2, characteristic Sm-centered f-f emission in 3 and 4, and excitation-dependent emission in LIII, 1, and 2. Furthermore, the time-dependent density functional theory (TD-DFT) study was carried out on the reported compounds to understand the nature of the emission peaks and the observed luminescence properties. The solid-state emission quantum yields of lanthanide complexes were also determined at different excitation wavelengths.

Single-Component Color-Tunable Gd(pic)3: Eu3+ Phosphor Based on a Metal-Organic Framework for Near-UV White-Light-Emitting Diodes.

Compared with their multicomponent analogues, single-component white-light-emitting diodes (WLEDs) can eliminate the disadvantages such as high cost, fluorescence self-absorption, poor machinability, and reproducibility, but how to produce white light with high quality in a single-phase host is still a big challenge. In the work, a series of Eu3+/Tb3+-doped Gd(pic)3 and La(pic)3 are obtained through solvothermal conditions with picolinic acid (Hpic) and lanthanide nitrate. Researchers could regularly modulate the emitting color of phosphors by adjusting the excitation wavelength as well as the relative concentration of Ln3+ ions to obtain white light. Different luminance values [especially quantum yield (QYs)] between host materials Gd(pic)3 and La(pic)3 are investigated, which shows that doping of Eu3+ into Gd(pic)3 can improve QY to a great extent. By employing Gd0.9512Eu0.0488(pic)3 and Gd0.9141Eu0.0451Tb0.0408(pic)3 as phosphors, we successfully fabricated two excellent near-ultraviolet (365 nm) WLEDs with CIE chromaticity coordinates (0.3052, 0.3462) and (0.3007, 0.3448), relatively low color-correlated temperature (6755, 7001 K), and high color rendering index (Ra = 71.8, 72.9). This approach may open a new prospect for developing single-phase near-ultraviolet phosphors with high efficiency.

Structure and Properties of “Type IV” Lanthanide Nitrate Hydrate:Urea Deep Eutectic Solvents

A series of lanthanide nitrate hydrate:urea “Type IV” deep eutectic solvents (DES; Ln = Ce, Pr, Nd) were prepared and their physical properties measured, showing very high surface tension and densi...

Mononuclear lanthanide complexes assembled from a tridentate NNO donor ligand: design of a DyIII single-ion magnet.

The reaction of a tridentate NNO donor ligand, 4-nitro-2-((2-(pyridine-2-yl)hydrazono)methyl)phenol (HL) with lanthanide(iii) nitrates in the presence of triethylamine afforded a new family of neutral mononuclear LnIII complexes [Ln(NO3)(L)2(HOCH3)] (Ln = Gd; (1) Tb; (2), Dy; (3), and Ho (4). The mononuclear complexes were structurally characterized by single crystal X-ray diffraction studies which revealed a spherical tricapped trigonal prism geometry with a pseudo D3h symmetry around the LnIII centre. Static (dc) and dynamic (ac) magnetic studies have been performed on these complexes. Field-induced single-ion magnet behaviour was observed in the DyIII analogue with an effective energy barrier and an pre-exponential factor of Δ/kB = 68(2) K and τ0 = 1.8 × 10-7 s, respectively.

Novel lanthanide(III) 4-methylbenzoylhydrazide complexes as precursors for lanthanide oxide nanophotocatalysts.

A series of metal complexes were prepared from separate reactions of lanthanide nitrate salts (La(iii), Ce(iii), Sm(iii), Gd(iii) and Ho(iii)) with 4-methylbenzoylhydrazide. The structures of the complexes were confirmed by analytical studies, spectral measurements and thermal studies. Complexes were formed with different stoichiometries of 1 : 2 and 1 : 3 (M : L). The ligand chelates by the nitrogen and oxygen atoms of the amino and carbonyl groups of the hydrazide moiety in the neutral keto form. The coordination compounds were converted to metal oxide nanoparticles (MONPs) through solid state thermal decomposition as monocular source precursors. The obtained MONPs were investigated via XRD, TEM and UV-Vis spectra. As a representative, CeO2 was utilized as a nanophotocatalyst to examine the photocatalytic activity of the MONPs for methylene blue (MB) photodegradation. CeO2 showed high removal of MB dye by 90.1% after UV illumination for 220 min. The reported method provides a generalized and systematic method for the preparation of many metal oxide nanoparticles with manageable and reproducible features.

A single-ion single-electron cerrous magnet.

Herein, we present monometallic Ln(iii) complexes [L3Ln(NO3)3] [where Ln = Ce (1) and La (2)] assembled from a simple reaction of the respective lanthanide nitrate hydrate and a bulky phosphonic diamide tBuPO(NHiPr)2 ligand (L), where complex 1 behaves as a single-ion single-electron magnet under a small applied magnetic field. The Ce(iii) ion occupies a nine-coordinate distorted muffin-like coordination environment. The combination of direct and Raman process dominates the relaxation dynamics in 1 under the applied dc field. The low-temperature measurements performed with oriented crystals on a micro-SQUID setup exhibits strong tunnelling at zero-field, consistent with the theoretical results where strong mixing of the ground state with higher excited mJ levels is detected and also throws additional insights on the relaxation dynamics of 1. Ab initio calculations have been performed to understand the origin of anisotropy and models have been proposed for future directions.

Modeling the Osmotic and Activity Coefficients of Lanthanide Nitrate Aqueous Solutions at 298.15 K from Low Molalities to Supersaturation

This article is a contribution to the modeling of the thermodynamic properties of 15 lanthanide (including lanthanum)-nitrate aqueous binary solutions, from low molalities to saturation (for Ce, Gd, Tb, and Tm) and supersaturation (for La, Pr, Nd, Sm, Eu, Dy, Ho, Er, Yb, and Lu) with respect to the corresponding trinitrate lanthanide solid salts. A critical compilation of the experimental and previous modeling data available in the literature is presented. The modeling approach is based on the standard Pitzer formulation for strong aqueous electrolytes, with two cases considered: three (beta((0)), beta((1)), and C-phi) or five (beta((0))), beta((1)), beta((2)), alpha(2), and C-phi) parameters. The best fits are obtained for the latter case, leading to the representation of unprecedented accuracy for the osmotic and activity coefficients over the whole range of experimental data up to the saturation/supersaturation points. On the basis of the models developed, the thermodynamic solubility product constants and the standard molar Gibbs free energy of formation of precipitating hexahydrate or pentahydrate lanthanide-nitrate solids are calculated.

Crystalline orthorhombic Ln[CO3][OH] (Ln=La, Pr, Nd, Sm, Eu, Gd) compounds hydrothermally synthesised with CO2 from air as carbonate source

Abstract Crystalline orthorhombic rare earth carbonate hydroxides Ln[CO3][OH] (Ln=La, Pr, Nd, Sm, Eu, Gd) were synthesised as phase pure powders via a simple hydrothermal reaction. CO2 from air acted as natural carbonate source and cetyltrimethylammonium bromide was added as templating agent to an aqueous rare earth nitrate solution. Single-crystal X-ray structure determination was performed on La[CO3][OH] (Pnma, a=7.4106(5), b=5.0502(3), c=8.5901(6) Å, 563 independent reflections, 38 refined parameters, wR2=0.037), Pr[CO3][OH] (Pnma, a=7.2755(4), b=4.9918(3), c=8.5207(5) Å, 744 independent reflections, 38 refined parameters, wR2=0.04), Eu[CO3][OH] (Pnma, a=7.1040(4), b=4.8940(3), c=8.4577(5) Å, 1649 independent reflections, 38 refined parameters, wR2=0.05) and Gd[CO3][OH] (Pnma, a=7.069(7), b=4.874(5), c=8.464(9) Å, 431 independent reflections, 38 refined parameters, wR2=0.051). These findings are supported by powder XRD, infrared spectroscopy, UV/Vis spectroscopy and, for Pr[CO3][OH] and Eu[CO3][OH], by measurements of the non-linear optical properties. Thermal analysis could demonstrate the possible use of the Ln[CO3][OH] phases as precursors for rare earth carbonate dioxides Ln 2[CO3]O2 and rare earth oxides Ln 2O3. The decomposition products inherit the precursor’s morphology. The lattice parameters of Pr2[CO3]O2 were refined from high-temperature powder XRD data.

Preparation of “NaREF4” phases from the sodium nitrate melt

Preparation of “NaREF4” compounds (RE = La-Lu, Y) from rare earth nitrates dissolved in molten NaNO3 has been studied at 350°C. Two-fold excess of sodium fluoride (NaF) was used as fluorinating agent. Hexagonal NaREF4 (RE = Pr-Lu, Y) phases isotypic with β-NaYF4 have been prepared. A mixture of CeF3 and NaCeF4 was obtained in cerium system, while only LaF3 phase was formed in lanthanum system.

Magnetic and luminescent coordination networks based on imidazolium salts and lanthanides for sensitive ratiometric thermometry.

The synthesis and characterization of six new lanthanide networks [Ln(L)(ox)(H2O)] with Ln = Eu3+, Gd3+, Tb3+, Dy3+, Ho3+ and Yb3+ is reported. They were synthesized by solvo-ionothermal reaction of lanthanide nitrate Ln(NO3)3·xH2O with the 1,3-bis(carboxymethyl)imidazolium [HL] ligand and oxalic acid (H2ox) in a water/ethanol solution. The crystal structure of these compounds has been solved on single crystals and the magnetic and luminescent properties have been investigated relying on intrinsic properties of the lanthanide ions. The synthetic strategy has been extended to mixed lanthanide networks leading to four isostructural networks of formula [Tb1−xEux(L)(ox)(H2O)] with x = 0.01, 0.03, 0.05 and 0.10. These materials were assessed as luminescent ratiometric thermometers based on the emission intensities of ligand, Tb3+ and Eu3+. The best sensitivities were obtained using the ratio between the emission intensities of Eu3+ (5D0→7F2 transition) and of the ligand as the thermometric parameter. [Tb0.97Eu0.03(L)(ox)(H2O)] was found to be one of the best thermometers among lanthanide-bearing coordination polymers and metal-organic frameworks, operative in the physiological range with a maximum sensitivity of 1.38%·K−1 at 340 K.

Tetraaqua[2,6-diacetylpyridine bis(semicarbazone)]samarium(III) trinitrate

The structure of tetraaqua[2,6-diacetylpyridine bis(semicarbazone)]samarium(III) trinitrate, [Sm(C11H15N7O2)(H2O)4](NO3)3, has monoclinic (P21/c) symmetry. The 2,6-diacetylpyridine (DAPSC) ligand is pentadentate. The coordination of the DAPSC ligand and four coordinated water molecules around the metal cation is best described as a distorted tricapped trigonal prism. The structure displays intermolecular hydrogen bonding. The structure is isomorphous with many other published lanthanide(III) nitrate salts with the DAPSC ligand, 2,6-diacetylpyridinebis(semicarbazone). One of the three nitrate counter-anions is disordered, which is consistent with the structures of other +3 lanthanide nitrate salts with DAPSC. Refinement of occupancies for the disordered nitrate group gave major and minor occupancies of 54.9 (14) and 45.1 (14)%, respectively.

Slow Magnetic Relaxation in Lanthanoid Crown Ether Complexes: Interplay of Raman and Anomalous Phonon Bottleneck Processes.

The combination of lanthanoid nitrates with 18-crown-6 (18-c-6) and tetrahalocatecholate (X4 Cat2- , X=Cl, Br) ligands has afforded two compound series [Ln(18-c-6)(X4 Cat)(NO3 )]⋅MeCN (X=Cl, 1-Ln; X=Br, 2-Ln; Ln=La, Ce, Nd, Gd, Tb, Dy). The 18-c-6 ligands occupy equatorial positions of a distorted sphenocorona geometry, whereas the charged ligands occupy the axial positions. The analogues of both series with Ln=Ce, Nd, Tb and Dy exhibit out-of-phase ac magnetic susceptibility signals in the presence of an applied magnetic field, indicative of slow magnetization relaxation. When diluted into a diamagnetic La host to reduce dipolar interactions, the Dy analogue exhibits slow relaxation up to 20 K in the absence of an applied dc field. Concerted magnetic measurements, EPR spectroscopy, and ab initio calculations have allowed elucidation of the mechanisms responsible for slow magnetic relaxation. A consistent approach has been applied to quantitatively model the relaxation data for different lanthanoid analogues, suggesting that the spin dynamics are governed by Raman processes at higher temperatures, transitioning to a dominant phonon bottleneck process as the temperature is decreased, with an observed T-6 rather than the usual T-2 dependence (T is temperature). This anomalous thermal dependence of the phonon bottleneck relaxation is consistent with anharmonic effects in the lattice dynamics, which was predicted by Van Vleck more than 70 years ago.

A Family of $$\left\{ {{\text{Ni}}^{\text{II}}_{2} {\text{Ln}}^{\text{III}}_{2} } \right\}$$ Ni 2 II Ln 2 III Butterfly Complexes: Lanthanide Contraction Effect on the Structures Magnetic Properties

Reactions of lanthanide nitrate, nickel nitrate, and polyhydroxyl Schiff-base ligand 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol (H4L) gave rise to a family of butterfly heterotetranuclear 3d–4f clusters formulated as [Ln2Ni2(H2L)2(μ3-OCH3)2(CH3CN)2(NO3)4]·2CH3OH·2H2O [Ln = Pr (1), Sm (2), Eu (3), Tb (4), Er (5)]. Single-crystal X-ray diffraction (XRD) reveals these complexes crystallize in the monoclinic space group P21/c. Both Ln1 and its symmetric Ln1A are coordinated to nine oxygen atoms and consist of two ligands with the same coordination mode μ3.η1:η2:η1:η2:η1, two nitrate ions and one μ3-OCH3. The five heterotetranuclear $${\text{Ni}}^{\text{II}}_{2} {\text{Ln}}^{\text{III}}_{2}$$ complexes display a central planar butterfly topology. The vertices of the body positions of the butterfly are occupied by NiII ions in all five complexes, which have been characterized by single-crystal X-ray diffraction, infrared spectroscopy, element analyses, powder X-ray diffraction and thermal gravimetric analyses. The magnetic properties of the complexes have been studied. The results show that complexes 1-3, and 5 exhibit antiferromagnetic exchange between the paramagnetic species, and 4 shows strong ferromagnetic interaction. We have shown the successful design and assembly of a new family of tetranuclear, dicationic, heterometallic $$\left\{ {{\text{Ni}}^{\text{II}}_{2} {\text{Ln}}^{\text{III}}_{2} } \right\}$$ complexes characterized by a butterfly-type topology. The results might be promoting the rational design and synthesis of 3d–4f molecule-base magnets materials with fascinating topologies and magnetic behaviours.