A variety of new tri- and tetranuclear Mn–Ln and Fe–Ln (Ln = lanthanide) complexes

The use of carboxylates in the synthesis of 3d/4f clusters, with or without a second organic ligand, has afforded a series of tetranuclear M₂Gd₂ complexes (M = Fe or Mn), and two new trinuclear M₂Gd (M = Fe or Mn) molecular compounds. Only one of these, [Mn₂Gd₂O₂(O₂CBu^t)₈(HO₂CBu^t)₄] (1), does not contain a multidentate chelate ligand. Two other similar tetranuclear clusters were synthesized from the use of triethanolamine (teaH₃) and 1,1,1-tris(hydroxymethyl)ethane (thmeH₃). [Mn₂Gd₂(OH)₂(O₂CPh)₄(NO₃)₂(teaH)₂] (2) has very similar structure with 1, bearing a defective incomplete double-cubane core bridged by μ₃-O atoms, whereas in the core of [NHEt₃]₂[Fe₂Gd₂(O₂CPh)₄(thme)₂(NO₃)₄] (3) the thme³⁻ ligand caps the two incomplete cubane units, providing the triply-bridging alkoxides needed for bridging. Two new oxide-centered triangular clusters were synthesized bearing the Schiff-based chelate 2-{[2-(dimethylamino)ethyl]methylamino}ethanol (dmemH), namely [Fe₂GdO(O₂CBu^t)₂(dmem)₂(NO₃)₃] (4), and [Mn₂GdO(O₂CBu^t)₂(dmem)₂(NO₃)₃] (5). Magnetic susceptibility measurements and/or reduced magnetization studies established that complexes 1 and 3 have an S = 5 ground state, complex 2 has S = 4, and complexes 4 and 5 are S = 7/2 in their ground states. These complexes portray the feasibility of obtaining products bearing metal cores commonly found in homometallic clusters, even when these include metals with completely different coordination chemistry and electronic structure, such as lanthanides.     

Oxidation resistance of LnSiON powders (Ln=Y,Gd and La)

For application of LnSiON (Ln=Y, Gd and La) oxynitride materials, e.g. as host-lattices for lamp phosphors, oxidation resistance up to about 600 °C in air is a prerequisite. In this study we prepared LnSiON (Ln=Y, Gd and La) powders by solid state reaction and observed via TGA/DTA-experiments that most compounds are oxidation resistant up to 600 °C in air. The stability in air at high temperatures increases going from Ln₅(SiO₄)₃N, Ln₄Si₂O₇N₂, LnSiO₂N, Ln₂Si₃O₃N₄ to Ln₃Si₈O₄N₁₁. This is explained by an increasing cross-linking between the siliconoxygennitrogen tetrahedra in this sequence. For the lattices with less cross-linking between the siliconoxygennitrogen tetrahedra we observed that the oxidation resistance decreases slightly going from Y and Gd to La. For these lattices, also, an additional weight gain was observed during the oxidation reaction, which was higher than expected for complete oxidation. The additional weight gain was ascribed to an intermediate phase in which nitrogen retention takes place.     

Syntheses and Crystal Structures of Three Coordination Complexes Based on Ln(Ⅲ) and mpca-Ligand

Three complexes obtained by the reaction of Pr(Ⅲ) or Nd(Ⅲ) salts with 5-methyl-2-pyrazinecarboxylic acid(Hmpca) are structurally determined by single-crystal X-ray diffraction.Complex [Pr(mpca-)3(H2O)2]2·6H2O(1) is composed of dinuclear Pr(Ⅲ) units with two metal centers bridged by two anionic mpca-ligands in a κ3O,O':O' bridging mode.Complexes [Pr(mpca-)3]n(2) and [Nd(mpca-)3]n(3) are isostructures,and they consist of polymeric chains based on Ln(Ⅲ) and mpca-ligands.Each pair of adjacent metal centers is linked by three mpca-molecules in a κ3N,O:O bridging mode.     

Synthesis,structure and magnetic properties of unsymmetrical dodecanuclear Mn–Ln clusters

Reaction of manganese acetate and lanthanide nitrates in the presence of excess of PhCOOH affords highly asymmetric dodecanuclear mixed-metal [Mn₁₀Ln₂(OH)(O)₈(PhCOOH)(PhCOO)₁₉] (Ln = Pr^III (1), Nd^III (2)) clusters. The similar reaction, but with only 2 equiv. of PhCOOH resulted in the compounds with higher nuclearity [Mn₁₁Eu₄(O)₈(OH)₈(PhCOO)₁₈(NO₃)₂(H₂O)₆]NO₃ · 4CH₃CN (3). Variable-temperature solid-state magnetic susceptibility of 1 and 2 in the temperature range 1.8–300 K were carried out, and for both complexes antiferromagnetic exchange interactions between the metal centers were observed, giving an estimated S = 17/2 ground state. AC magnetic susceptibility data have revealed out-of-phase signals, which suggest that these complexes exhibit a slow relaxation of magnetization as observed in single-molecule magnets.     

Ce10Cl4Ga5 and Ln3ClGa4 (Ln = La,Ce): reduced halides or oxidized intermetallics?

The compounds Ce(10)Cl(4)Ga(5) and Ln(3)ClGa(4) (Ln = La, Ce) were synthesized from stoichiometric mixtures of Ln, LnCl(3), and Ga under Ar atmosphere in sealed Ta ampules at 910-1020 degrees C for 25-26 days. Ce(10)Cl(4)Ga(5) is isostructural to La(10)Cl(4)Ga(5) (space group I4/mcm, No. 140) with lattice constants a = 7.9546(11) A, c = 31.793(6) A. Ln(3)ClGa(4) represents a new structural type, also in the space group I4/mcm, with a = 8.1955(8) and 8.1123(11) A, c = 11.363(2) and 11.229(2) A, respectively, for Ln = La and Ce. Ce(10)Cl(4)Ga(5) features building blocks of Ga-centered Ce(6) trigonal prisms and distinctive two-dimensional intermetallic CuAl(2) and U(3)Si(2) type nets. Its electronic structure falls within the realm of reduced rare-earth halides. Ln(3)ClGa(4) also contains the intermetallic CuAl(2) type nets, but the interstitials are inverted: The building blocks are Cl-centered Ln(6) octahedra. Its electronic structure is characterized by strong peripheral Ln-Ga bonding stabilizing the Ln(6)Cl octahedron which normally would have its Ln-Ln antibonding orbitals filled with electrons from interstitials beyond chalcogen. Magnetic susceptibility and conductivity measurements confirm the metallic nature of all three compounds.     

Ln(III)-MOFs (Ln = Tb,Eu, Dy,and Sm) based on triazole carboxylic ligand with carboxylate and nitrogen donors with applications as chemical sensors and magnetic materials

Abstract

Using a triazole carboxylic ligand (H₂L = 4-(1H-1,2,4-triazol-1-yl) isophthalic acid), four water-stable lanthanide metal–organic frameworks (Ln(III)-MOFs) (1-Ln, Ln(III) = Tb, Eu, Dy, and Sm), [Ln(L)(HL)(H₂O)₂], where the deprotonated H₂L ligands have two different coordination modes: L^2? and HL^? [(a): η²μ₂χ², η²μ₁χ²; (b): η²μ₁χ²], have been synthesized by solvothermal reaction and characterized by elemental analysis, FT-IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Single-crystal X-ray diffraction analyses show that Ln(III)-MOFs are isostructural with 2D-layered structures with uncoordinated carboxylic and triazole groups. The luminescent properties of 1-Tb in aqueous solution containing different cationic solutions and small organic solvents have been explored under ultraviolet irradiation at room temperature. The high quenching constant K_SV values and low detection limits indicate that 1-Tb exhibits extremely high detection sensitivity and selectivity toward Fe³⁺ ions and nitrobenzene; 1-Tb can keep its original network and be reused after the sensing experiments, which provide us with an optical material for detecting Fe³⁺ ions and nitrobenzene. Magnetic studies show that antiferromagnetic exchange interactions exist between Dy(III) ions in 1-Dy.     

Homogeneity ranges for yttrium and holmium manganites Ln2−x Mn x O3±δ (Ln = Y, Ho) in air

The homogeneity ranges with respect to the content of metal components in air were determined for yttrium and holmium manganites, based on X-ray phase analysis data for homogeneous solid solutions and heterogeneous compositions with the general formula Ln_2?x Mn _x O_3±δ (Ln = Y, Ho) prepared by ceramic synthesis procedure in air at 900–1400°C. The results were presented as fragments of the composition-temperature phase diagrams of the Ln-Mn-O (Ln = Y, Ho) systems in air.     

Re-dispersion and film formation of GdVO4 : Ln3+ (Ln3+ = Dy3+, Eu3+, Sm3+, Tm3+) nanoparticles: particle size and luminescence studies

GdVO(4)?:?Ln(3+) (Ln(3+) = Dy(3+), Eu(3+), Sm(3+), Tm(3+)) nanoparticles are prepared by a simple chemical route at 140 °C. The crystallite size can be tuned by varying the pH of the reaction medium. Interestingly, the crystallite size is found to increase significantly when pH increases from 6 to 12. This is related to slower nucleation of the GdVO(4) formation with increase of VO(4)(3-) present in solution. The luminescence study shows an efficient energy transfer from vanadate absorption of GdVO(4) to Ln(3+) and thereby enhanced emissions are obtained. A possible reaction mechanism at different pH values is suggested in this study. As-prepared samples are well dispersed in ethanol, methanol and water, and can be incorporated into polymer films. Luminescence and its decay lifetime studies confirm the decrease in non-radiative transition probability with the increase of heat treatment temperature. Re-dispersed particles will be useful in potential applications of life science and the film will be useful in display devices.     

A series of heterobimetallic Ni(II)–Ln(III) (Ln = La,Ce, Pr and Nd) coordination polymers derived from 3-EtOsalamo and dicarboxylates: syntheses,crystal structures and fluorescence properties

Transition Metal Chemistry - Four coordination polymers ∞2 [Ni(DMF)(L)Ln(bdc)1.5] (Ln?=?La (1) and Nd (4)) and ∞2 [Ni2(DMF)2(L)2Ln2(bdc)3]·CH3OH (Ln?=?Ce...     

Thermal decomposition of Ln(C2H5CO2)3·H2O (Ln?=?Ho, Er, Tm and Yb)

The thermal decomposition of Ho(III), Er(III), Tm(III) and Yb(III) propionate monohydrates in argon was studied by means of thermogravimetry (TG), differential thermal analysis (DTA), IR-spectroscopy and X-ray diffraction (XRD). Dehydration takes place around 90?°C. It is followed by the decomposition of the anhydrous propionates to Ln₂O₂CO₃ (Ln?=?Ho, Er, Tm or Yb) with the evolution of CO₂ and 3-pentanone (C₂H₅COC₂H₅) between 300 and 400?°C. The further decomposition of Ln₂O₂CO₃ to the respective sesquioxides Ln₂O₃ is characterized by an intermediate plateau extending from approximately 500?C700?°C in the TG traces. This stage corresponds to an overall composition of Ln₂O_2.5(CO₃)_0.5 but is more probably a mixture of Ln₂O₂CO₃ and Ln₂O₃. The stability of this intermediate state decreases for the lighter rare-earth (RE) compounds studied. Full conversion to Ln₂O₃ is achieved at about 1,100?°C. The overall thermal decomposition behaviour of the title compounds is similar to that previously reported for Lu(C₂H₅CO₂)₃·H₂O.     

Syntheses,Structures and Band Gaps of KLnSiS4 （Ln = Sm,Yb）

Two new quaternary sulfides, KSmSiS4 （1） and KYbSiS4 （2）, have been synthesized by high-temperature solid-state reaction. Single,crystal X-ray diffraction analyses indicate that both compounds crystallize in the space group P21/m, and the crystal data are as follows： a = 6.426（11）, b = 6.582（11）, c = 8.602（15）A, β= 107.90（13）°, Z = 2, V= 346.2（10） A^3, Dc = 3.317 g/cm^3, F（000） = 318,μ（MoKα） = 10.334 mm^-1, the final R = 0.0559 and wR = 0.1370 for 1; and α= 6.3244（10）, b = 6.5552（10）, c = 8.5701（15）A, β= 108.001（13）°, Z = 2, V = 337.91（9） A^3, De= 3.621 g/cm^3, F（000） = 334, μ（MoKα） = 15.737 mm^-1, the final R = 0.0422 and wR = 0.0960 for 2. The KLnSiS4 （Ln = Sm, Yb） structure consists of corrugated ∞^2 [LnSiS4]^- layers which are formed by edge-sharing LnS8 bicapped trigonal prisms and SiS4 tetrahedra. The K^＋ cations are located in the cavities defined by S2 anions between the ∞^2[LnSiS4]^- layers. Band-gap analyses show that compounds 1 and 2 are semiconductors with optical band-gaps of 2.40 and 2.34 eV, respectively.     

Hydrothermal Synthesis,Crystal Structures,and Fluorescence Properties of Ni(II)–Ln(III) Complexes (Ln = Sm,Pr, Eu)

Three novel 3d–4f heterometal complexes [Ln(NiL)₃(Btca)(NO₃)] · xH₂O (Ln = Sm(III) (I), Pr(III) (II), Eu(III) (III) (H₂L = 2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien, H₂Btca = benzotriazole-5-carboxylic acid) were solvothermally synthesized and characterized by singlecrystal X-ray diffraction (CIF files CCDC nos. 1555557 (I), 1555555 (II), 1555556 (III)). They crystallized in the monoclinic space group P2₁/n for I (x = 1.5) and C2/c for (II) and (III) (x = 1), respectively. In these complexes, the central Ln(III) and external nickel ions are bridged by macrocyclic oxamide groups. The metal center of Ln(III) resides in a distorted bicapped square antiprism surrounding with six oxygen atoms of three oxamide groups, two oxygen atoms of Btca^2– ion and two oxygen atoms of NO₃^-. Furthermore, there are C–H···O and/or C–H···N hydrogen bond interactions among nitrate, benzotriazole-5-carboxylate, macrocyclic oxamide and water to form three-dimensional superamolecular architecture. The fluorescence properties of the compounds I and II are also discussed.     

四方相LaVO_4：Ln（Ln=Nd/Er）近红外发光纳米材料的水热合成

本文通过EDTA辅助的水热法合成了四方相稀土矾酸盐一维纳米材料,并通过Nd3＋或Er3＋掺杂使其具有近红外发光性质.与利用柠檬酸根作为配体合成得到的单斜相纳米晶相比,四方相矾酸盐具有更高的发光强度.通过对反应条件的改变,分别考察了EDTA-稀土离子投料比和掺杂离子浓度对产物形貌及发光性质的影响,发现在纳米尺度下,稀土离子具有更高的猝灭浓度.     

Synthesis and structural characterization of lanthanide oxalate–oxydiacetate mixed-ligand coordination polymers {[Ln(oda)(H2O) x ]2(ox)} n ( x = 3 for Ln = La,Ce, Pr,Gd, Tb and x = 2 for Ln = Er)

Reactions of oxydiacetic acid (H₂oda) with lanthanide oxide, nitrate, chloride, and carbonate gave six lanthanide oxalate–oxydiacetate mixed-ligand coordination polymers {[Ln(oda)(H₂O) _x ]₂(ox)} _n [x = 3 for Ln = La, Ce, Pr, Gd, Tb, (1–5), and x = 2 for Ln = Er (6)]. Oxydiacetic acid is decomposed into oxalic acid in this reaction. In the crystal structures of 1–6, oxydiacetate and the lanthanides build a chain, and the oxalate groups bridge two chains to form 1-D double-chain ladder-shaped structures, connected by intermolecular hydrogen bonds to form a 2-D network structure. These compounds contain approximately 3.0 × 6.4 Ų channels along the c-axis. The infrared spectra and thermal behaviors of 1–6 are also investigated.     

Synthesis and Characterization of -[（C5H4SiMe2^tBu）2Ln（μ-S^nBu）]2 （Ln = Y,Er）

（C5H4SiMe2^tBu）2Ln^nBu reacted with 1 equiv, of elemental sulfur in toluene at ambient temperature to yield the corresponding lanthanocene thiolates [（C5H4SiMe2^tBu）2Ln（μ-S^nBu）]2 （Ln = Y （1）, Er （2））. Complexes 1 and 2 have been characterized by elemental analysis, IR, mass spectroscopy and X-ray single-crystal diffraction analysis. Both complexes are of monoclinic with space group P21/c, formula C52H94S2Si4Y2 1 （C52H94S2Si4Er2 2） Mr = 1073.57 （1230.27）, a = 8.495（2） （8.41（2））, b = 26.913（8） （26.67（7））, c = 13.756（4） （13.68（4）） A, α = 90（90）, β = 101.184（5） （101.57（4））, γ = 90 （90）°, V= 3085.1（15） （3007（14）） A^3, Dc = 1.156 （1.359） g·cm^-3, Z= 2 （2）, F（000） = 1144 （1260）, μ = 2.046 （2.951） cm^-1, R = 0.0687 （0.0749） and wR = 0.1306 （0.1507） for observed reflections with I 〉 2σ（I）. X-ray structures of 1 and 2 definitively prove that only one sulfur atom is inserted into the Ln-C（^nBu） bond, forming a thiolate ligand.     

Structural Order–Disorder Transitions in Ln2Ti2O7 (Ln = Lu,Gd)

The phase generation in the Lu(Gd)–Ti–O systems is studied at 20–1000° using a co-precipitation method. During a thermal treatment of co-precipitation products after a sublimation dehydration, for a composition with the Lu : Ti cation ratio of 1 : 1, an Lu₂Ti₂O₇ phase with a fluorite structure forms at 650°. At 730–750°C the phase undergoes a fluorite pyrochlore transition. Above 750°C its structure is that of disordered pyrochlore, in which antistructural defects occur in Lu and Ti positions (up to 18%). Above 900°C the structure of pyrochlore becomes ordered, and the number of defects in Lu and Ti positions decreases, which affects the temperature dependence of permittivity of Lu₂Ti₂O₇. In Gd–Ti–O system, Gd₂Ti₂O₇ is crystallized, which has a pyrochlore structure only at 740–900°. Electroconductivity and permittivity of Lu₂Ti₂O₇ and Gd₂Ti₂O₇ are measured.     

A Double Addition of LnH to a Carbon-Carbon Triple Bond and Competitive Oxidation of Ytterbium(II) and Hydrido Centers

Addition of two Ln?H bonds of an Yb(II) hydrido complex supported by bulky amidinate ligand to a C?C bond lead to the formation of 1,2-dianionic bibenzyl fragment. Both Yb(II) and hydrido centers are oxidized under the reaction conditions. The resulting Yb(II) -η(6) -arene interaction is surprisingly robust: the arene cannot be replaced from the metal coordination sphere when treated with Lewis bases.     

Synthesis and Crystal Structure of [Cp_2Ln(OC(SEt)NPh )]_2

1 INTRODUCTION The insertion of unsaturated molecules into the lanthanide-ligand bond has attracted considerable attention, because it is a fundamental step for many metal-promoted transformations, in which some va- luable new methods for the formation of carbon- carbon and carbon-heteroatom bonds can be deve- loped and some complexes with novel structures or peculiar characters can be obtained[1~4]. Notably, in contrast to the wide reaction chemistry of organo- lanthanide alkyl (aryl), am…