Defect-dicubane Ni2Ln2 (Ln = Dy, Tb) single molecule magnets

Two pairs of Ni(2)Dy(2) and Ni(2)Tb(2) complexes, [Ni(2)Ln(2)(L)(4)(NO(3))(2)(DMF)(2)] {Ln = Dy (1), Tb (2)} and [Ni(2)Ln(2)(L)(4)(NO(3))(2)(MeOH)(2)]·3MeOH {Ln = Dy (3), Tb (4)} (H(2)L is the Schiff base resulting from the condensation of o-vanillin and 2-aminophenol) possessing a defect-dicubane core topology were synthesized and characterized. All four complexes are ferromagnetically coupled, and the two Dy-analogues are found to be Single Molecule Magnets (SMMs) with energy barriers in the range 18-28 K. Compound 1 displays step-like hysteresis loops, confirming the SMM behavior. Although 1 and 3 show very similar structural topologies, the dynamic properties of 1 and 3 are different with blocking temperatures (3.2 and 4.2 K at a frequency of 1500 Hz) differing by 1 K. This appears to result from a change in orientation of the nitrate ligands on the Dy(III) ions, induced by changes in ligands on Ni(II).     

Darstellung und Kristallstrukturen von Ln2Al3Si2 und Ln2AlSi2 (Ln: Y,Tb–Lu)

Synthesis and Crystal Structures of Ln ₂Al₃Si₂ and Ln ₂AlSi₂ ( Ln : Y, Tb–Lu) Eight new ternary aluminium silicides were prepared by heating mixtures of the elements and investigated by means of single‐crystal X‐ray methods. Tb₂Al₃Si₂ (a = 10.197(2), b = 4.045(1), c = 6.614(2) Å, β = 101.11(2)°) and Dy₂Al₃Si₂ (a = 10.144(6), b = 4.028(3), c = 6.580(6) Å, β = 101.04(6)°) crystallize in the Y₂Al₃Si₂ type structure, which contains wavy layers of Al and Si atoms linked together by additional Al atoms and linear Si–Al–Si bonds. Through this there are channels along [010], which are filled by Tb and Dy atoms respectively. The silicides Ln₂AlSi₂ with Ln = Y (a = 8.663(2), b = 5.748(1), c = 4.050(1) Å), Ho (a = 8.578(2), b = 5.732(1), c = 4.022(1) Å), Er (a = 8.529(2), b = 5.719(2), c = 4.011(1) Å), Tm (a = 8.454(5), b = 5.737(2), c = 3.984(2) Å) and Lu (a = 8.416(2), b = 5.662(2), c = 4.001(1) Å) crystallize in the W₂CoB₂ type structure (Immm; Z = 2), whereas the structure of Yb₂AlSi₂ (a = 6.765(2), c = 4.226(1) Å; P4/mbm; Z = 2) corresponds to a ternary variant of the U₃Si₂ type structure. In all compounds the Si atoms are coordinated by trigonal prisms of metal atoms, which are connected by common faces so that Si₂ pairs (d_Si–Si: 2.37–2.42 Å) are formed.     

Kinetics of the transformation of Ln2O2SO4 into Ln2O2S (Ln = La, Pr, Nd, and Sm) in a hydrogen flow

The kinetic dependences of the yield of Ln₂O₂S (Ln = La, Pr, Nd, and Sm) upon the treatment of Ln₂O₂SO₄ in a hydrogen flow at 950, 1120, and 1170 K are constructed. The plots are approximated by Avrami-Erofeev equations, equations of compressed volume and compressed surface, and Jander’s equation. The correctness of choosing these equations is evaluated using the numerical values of Fisher’s criterion. Images of the particles of Nd₂O₂SO₄ → Nd₂O₂S transformation in the flow are obtained on an Ntegra Aura atomic force probe microscope. A mechanism of the crystal growth of the Nd₂O₂S phase from the nucleation site of the Nd₂O₂SO₄ and Nd₂O₂S phase boundaries is proposed.     

The thermodynamic properties of Ln2BaO4 (Ln = Sm, Dy, Ho)

The thermodynamic properties of the Ln₂BaO₄ phases (Ln = Dy, Ho, Sm) were studied by the electromotive force method with a fluoride electrolyte (890–1180 K), solution calorimetry in 1.07 N hydrochloric acid at 298.15 K, and differential scanning calorimetry (298–860 K). The experimental data were jointly processed, and the thermodynamic functions of the compounds over the temperature range 298–1200 K were calculated.     

Trapping of anionic organic radicals by (TpMe2)2Ln (Ln = Sm, Eu)

Stoichiometric reaction of [ Sm(Tp(Me2))2 ], 1, with a variety of reducible ketone- and quinone-type substrates gave thermally stable, isolable radical anions/ketyls in moderate to good yields. Thus reaction with benzophenone gave [Sm(Tp(Me2))2(OCPh2)], 2, with fluorenone [Sm(Tp(Me2))2(eta1-OC13H8)], 3, and di-tert-butylparaquinone [Sm(Tp(Me2))2(eta1-OC6H2(tBu)2O)], 4, each of which was structurally characterized. In the case of the less-hindered benzoquinone, an unimetallic semiquinone [Sm(Tp(Me2))2(OC6H4O)], 5, could be isolated, although it was unstable with respect to formation of the dimetallic complex [Sm(Tp(Me2))2]2(mu-OC6H4O), 6. Compound 6 was structurally characterized, as was its anthraquinone analogue [Sm(Tp(Me2))2]2(mu-OC14H8O), 7. When the analogous reaction was carried out between the less-reducing [Eu(Tp(Me2))2] and benzoquinone, only the europium analogue of the semiquinone 5, [Eu(Tp(Me2))2(OC6H4O)], 8, could be isolated. The use of the sterically hindered 3,5-di-tert-butyl-o-benzoquinone allowed isolation of [Sm(Tp(Me2))2(DTBSQ)], 9.     

Diplatinum alkynyl chromophores as sensitisers for lanthanide luminescence in Pt2Ln2 and Pt2Ln4 (Ln = Eu, Nd, Yb) arrays with acetylide-functionalized bipyridine/phenanthroline

Incorporation of diplatinum complex Pt2(micro-dppm)2(bpyC[triple bond]C)4 or Pt2(mu-dppm)2(phenC[triple bond]C)4 with Ln(hfac)3(H2O)2 (Ln = Nd, Eu, Yb) gave a series of Pt2Ln2 and Pt2Ln4 bimetallic arrays, in which the excitation of d(Pt) -->pi*(R-C[triple bond]C) MLCT absorption induces sensitisation of lanthanide luminescence through efficient d --> f energy transfer from Pt(II) alkynyl chromophores.     

1-D polymers with alternate Cu2 and Ln2 units (Ln = Gd, Er, Y) and carboxylate linkages

Three isostructural Cu 2Ln 2 1-D polymers [Cu 2Ln 2L 10(H 2O) 4.3H 2O] n where Ln = Gd ( 1), Er ( 2), and Y ( 3) and HL= trans-2-butenoic acid, were synthesized and characterized by X-ray crystallography, electron paramagnetic resonance, and magnetic measurements. Pairs of alternate Cu 2 and Ln 2 dinuclear units are combined into a linear array by a set of one covalent eta (2):eta (1):mu 2 carboxylate oxygen and two H bonds, at Cu...Ln distances of ca. 4.5 A. These units exhibit four eta (1):eta (1):mu 2 and two eta (2):eta (1):mu 2 carboxylate bridges, respectively. Magnetic measurements between 2 and 300 K, fields B 0 = mu 0 H between 0 and 9 T, and electron paramagnetic resonance (EPR) measurements at the X-band and room temperature are reported. The magnetic susceptibilities indicate bulk antiferromagnetic behavior of the three compounds at low temperatures. Magnetization and EPR data for 1 and 3 allowed evaluation of the exchange couplings between both Cu and Gd ions in their dinuclear units and between Cu and Gd neighbor ions in the spin chains. The data for the isolated Cu 2 units in 3 yield g || = 2.350 and g [symbol: see text] = 2.054, J Cu-Cu = -338 (3) cm (-1) for the exchange coupling [ H ex(1,2) = - J 1-2 S1 x S2], and D 0 = -0.342 (0.003) cm (-1) and E 0 = 0.003 (0.001) cm (-1) for the zero-field-splitting parameters of the triplet state arising from anisotropic spin-spin interactions. Considering tetranuclear blocks Gd-Cu-Cu-Gd in 1, with the parameters for the Cu 2 unit obtained for 3, we evaluated ferromagnetic interactions between Cu and Gd neighbors, J Cu-Gd = 13.0 (0.1) cm (-1), and between Gd ions in the Gd 2 units, J Gd-Gd = 0.25 (0.02) cm (-1), with g Gd = 1.991. The bulk antiferromagnetic behavior of 1 is a consequence of the antiferromagnetic coupling between Cu ions and of the magnitude, |J Cu-Gd|, of the Cu-Gd exchange coupling. Compound 2 displays a susceptibility peak at 15 K that may be interpreted as the combined result from antiferromagnetic couplings between Er (III) ions in Er 2 units and their coupling with the Cu 2 units.     

Phase diagrams of the systems Ln2S3-Ln2O3 (Ln = Gd, Dy)

For the first time, the phase diagrams of the systems Gd₂S₃-Gd₂O₃ and Dy₂S₃-Dy₂O₃ were constructed within the temperature range from 870 K to the melting point. In the systems, compounds Gd₂O₂S and Dy₂O₂S form in hexagonal symmetry with the unit cell parameters a = 0.3858 nm, c = 0.6667 nm and a = 0.3802 nm, c = 0.6591 nm, respectively. The compounds melt congruently at 2430 and 2370 K, respectively. Their microhardnesses are 4900 and 5150 MPa, respectively. The coordinates of eutectics are the following: 21 mol % Gd₂O₃, T _eu = 1875 K; 83 mol % Gd₂O₃, T _eu = 2270 K; 20 mol % Dy₂O₃, T _eu = 1780 K; and 81 mol % Dy₂O₃, T _eu = 2220 K.     

Crystal structure and magnetism of layered Ln2Ca2MnNiO8 (Ln=Pr,Nd, Sm,and Gd) compounds

We report the syntheses, crystal structure, and magnetic properties of a series of distorted K₂NiF₄-type oxides Ln₂Ca₂MnNiO₈ (Ln=Pr, Nd, Sm, and Gd) in which Ln/Ca and Mn/Ni atoms randomly occupy the K and Ni sites respectively. The Ln=La compound does not form. These compounds show systematic distortions from the ideal tetragonal K₂NiF₄ structure (space group I4/mmm) to an orthorhombic structure (space group Pccn) with buckled MO₂ (M=Mn/Ni) layers. The degree of distortion is increased as the size of Ln decreases. Based on the magnetic data and X-ray absorption near edge spectra, we assigned Mn^IV and Ni^II. The Curie–Weiss plots of the high temperature magnetic data suggest strong ferromagnetic interactions probably due to Mn^IV–O–Ni^II linkages, implying local ordering of Mn/Ni ions to form ferromangnetic clusters in the MO₂ layers. At low temperatures below 110–130 K, these compounds show antiferromagnetic behaviors because of Mn^IV–O–Mn^IV and/or Ni^II–O–Ni^II contacts between the ferromagnetic clusters. The Ln=Pr and Nd compounds show additional antiferromagnetic signals that we attribute to the interlayer interactions between the clusters mediated by the Pr³⁺ and Nd³⁺ ions in the interlayer spaces. The present compounds show many parallels with the previously reported Ln₂Sr₂MnNiO₈ compounds.     

Kinetic diagrams of Ln2O2SO4 phase transformations in a H2 flow (Ln = La, Pr, Nd, Sm)

Kinetic diagrams of Ln₂O₂SO₄ (Ln = La, Pr, Nd, Sm) systems reduction in a H₂ flow are plotted for the first time in temperature-duration of treatment coordinates in which there are five areas of phase states. The temperatures of formation are established for products of the Ln₂O₂SO₄ + 4H₂ = Ln₂O₂S + 4H₂O reaction in the temperature range of 880–900 K and products of the Ln₂O₂SO₄ + H₂ = Ln₂O₃ + SO₂+ H₂O reaction in the temperature range of 1090–1220 K. The ranges of the temperature of formation of the homo-geneous Ln₂O₂S phase were found to decrease: 880–1220, 900–1200, 900–1180, and 900–1090 K in the sequence La-Pr-Nd-Sm.     

Lanthanoidtellurate Ln2TeO6

Lanthanoid Tellurates Ln₂TeO₆ The crystal structure of La₂TeO₆, orthorhombic, a = 551.0, b = 944.1, c = 1038.7 pm, and crystallographic data of other isostructural lanthanoid tellurates (up to Yb₂TeO₆) formerly described as hexagonal, have been determined. For a second modification of the Yb compound, the Na₂SiF₆ structure has been confirmed.     

高温高压法提取金属富勒烯Lnm@C2nLn=Y, Gd, Tb)

笼内金属富勒烯以其独特的结构性质和潜在的应用价值而引起了人们极大的注意 [1～ 3] ,但因制备技术复杂、产率低以及将其从伴生的空心富勒烯中分离出来比较困难而使其研究受到很大的限制 .笼内金属富勒烯的分离提取始终是金属富勒烯研究的一个重要分支 .通常的方法是将放电得到的烟炱采用甲苯索氏提取的方法粗提 ,然后用高压液相色谱法分离得到纯品 ,笼内金属富勒烯的产率仅为烟炱的 0 .1 % [4～ 6] .我们改进了常规的提取方法 ,建立了一种新的提取方法—高温高压提取法 .具体的做法是采用甲苯索氏提取法从烟炱中提取出空心富勒烯和少量金…     

Magnetic properties of Ln2−xLn′xCo17 compounds (Ln = Gd,Dy, Ho,or Er,Ln′ = Th or Ce)

Magnetic and structural characteristics of the ternary systems Ln_2?xTh_xCo₁₇ (Ln = Gd, Dy, Ho, and Er) and Ln_2?xCe_xCo₁₇ (Ln = Gd, Dy, and Ho) are presented. Incorporation of Th in the lattice stabilizes the Th₂Zn₁₇ structure, whereas incorporation of Ce does not; if the binary system has the Th₂Ni₁₇ structure the incorporation of Ce leaves the structure unchanged. The antiferromagnetic LnCo coupling observed in the Ln₂Co₁₇ systems persists in the ternary alloys. The moment of the cobalt sublattice is decreased when more than half of the Ln is replaced by Th, suggesting that the extra electron contributed by Th enters the Co d-band or d-shell. The direction of easy magnetization is in the basal plane for all composition in the Gd, Dy, and Ho systems. In Er_2?xTh_xCo₁₇ the easy direction is along the c-axis for x = 0 and 0.2, but is in the basal plane for higher thorium contents.     

Mechanisms of the Solid-State Synthesis of Ln2SrFe2O7 (Ln = La,Nd, Gd,Dy) Layered Perovskite-Related Phases

Russian Journal of General Chemistry - The formation mechanisms for a series of n = 2 Ruddlesden-Popper phases Ln2SrFe2O7 (Ln = La, Nd, Gd, Dy) in the Ln2O3-SrO-Fe2O3 systems were determined. The...     

Reactions of lanthanoid metals with 3,5-diphenylpyrazole at elevated temperatures: synthesis and structures of both homoleptic, [Ln3(Ph2pz)9] (Ln = La, Nd), [Ln2(Ph2pz)6] (Ln = Er, Lu), and heteroleptic, [Ln(Ph2pz)3(Ph2pzH)2] (Ln = La, Nd, Gd, Tb, Er or Yb), pyrazolate complexes

The direct reaction of lanthanoid metals with 3,5-diphenylpyrazole (Ph2pzH) at 300 degrees C under vacuum in the presence of mercury gives the structurally characterized [Ln3(Ph2pz)9] (Ln = La or Nd), [Ln2(Ph2pz)6] (Ln = Er or Lu). Similar reactions provided heteroleptic [Ln(Ph2pz)3(Ph2pzH)2] (Ln = La, Nd, Gd, Tb, Er and Y). The last was obtained only from impure Ph2pzH, but was subsequently prepared by treatment of [Yb(Ph2pz)3(thf)2] with Ph2pzH. Reactions of Yb with Ph2pzH at 200 degrees C gave a poorly soluble divalent species which was converted by 1,2-dimethoxyethane into [Yb(Ph2pz)2(dme)2]. Single crystal X-ray structures established a bowed trinuclear pyrazolate-bridged structure for [Ln3(Ph2pz)9] (Ln = La or Nd), Ln...Ln...Ln being 135.94(1) degrees (La) and 137.41(1) degrees(Nd). There are two eta2-Ph2pz ligands on the terminal Ln atoms and one on the central metal with adjacent Ln atoms linked by one mu-eta2:eta2 and one mu-eta5 (to terminal Ln):eta2 pyrazolate group. Thus the terminal Ln atoms are formally nine-coordinate and the central Ln, ten-coordinate. By contrast, [Ln2(Ph2pz)6] (Ln = Er or Lu) complexes are dimeric with two terminal (eta2) and two bridging (mu-eta2:eta2) pyrazolates and eight-coordinate lanthanoids. All six heteroleptic complexes [Ln(Ph2pz)3(Ph2pzH)2] (Ln = La, Nd, Gd, Tb, Er or Yb) are isomorphous with three equatorial eta2-Ph2pz groups, transoid(N-Ln-N 158.18(6)-161.43(9) degrees) eta1-pyrazole ligands, and eight-coordinate Ln throughout.     

Phase equilibrium and p s-T-x diagrams of the Ln2S3-LnS2 (Ln = La, Pr, Nd, Sm-Er) systems

A new methodology is proposed and the phase equilibrium is investigated in the Ln₂S₃-LnS₂ systems, in which the low-temperature behavior of nonstoichiometric phases is controlled by the kinetics of the ordering of defects. It is shown that, under equilibrium conditions, the phase equilibrium in the systems is represented not only by a polysulfide with a wide homogeneity region, but also by several (or one) phases of constant irrational compositions combined in the homologous series Ln_nS_2n?1 (n = 3, 4, 7, 8, and 10). The formation of sulfur vacancies and isolated [S₂]^2? ions (which compensate the charge) in the anionic S^2? layer is the basic mechanism of changing the composition of the members of the series. On the basis of structural data, the possible mechanisms of the ordering of defective LnS_2?x polysulfides are examined and it is shown that the formation of stable or metastable phases is a kinetics-controlled process. The role of p _s-T-x diagrams in the interpretations of complex structures of metastable phases from the point of view of attainment of the equilibrium state is discussed.     

Precursor approach to lanthanide dioxo monocarbodiimides Ln2O2CN2 (Ln=Y, Ho, Er, Yb) by insertion of CO2 into organometallic Ln-N compounds

We present two organometallic precursor approaches leading to the hitherto-unknown dioxo monocarbodiimides (Ln(2)O(2)CN(2)) of the late lanthanides Ho, Er, and Yb as well as yttrium. One involves insertion of CO(2), and the other one is a straightforward route using a molecular single-source precursor. To this end the reactivity of the activated amido lanthanide compound [(Cp(2)ErNH(2))(2)] towards carbon dioxide absorption under supercritical conditions was studied. Selective insertion of CO(2) into the amido complex yielded the single-source precursor [Er(2)(O(2)CN(2)H(4))Cp(4)], which was characterized by vibrational spectroscopy and thermal and elemental analyses. Ammonolysis of this amorphous compound at 700 degrees C affords Er(2)O(2)CN(2). To gain deeper insight into the structural characteristics of the amorphous precursor, a similar molecular carbamato complex was synthesized and fully characterized. X-ray structure analysis of the dimeric complex [Cp(4)Ho(2){mu-eta(1):eta(2)-OC(OtBu)NH}] shows an unusual bonding mode of the tert-butylcarbamate ligand, which acts as both a bridging and side-on chelating group. Ammonolysis of this compound also yielded dioxo monocarbodiimides, and therefore the crystalline carbamato complex turned out to be an alternative precursor for the straightforward synthesis of Ln(2)O(2)CN(2). Analogously, the dioxo monocarbodiimides of Y, Ho, Er, and Yb were synthesized by this route. The crystal structures were determined from X-ray powder diffraction data and refined by the Rietveld method (Ln=Ho, Er). Further spectroscopic characterization and elemental analysis evidenced the existence of phase-pure products. The dioxo monocarbodiimides of holmium and erbium crystallize in the trigonal space group P[over]3m1. According to X-ray powder diffraction, they adopt the Ln(2)O(2)CN(2) (Ln=Ce-Gd) structure type.     

Synthesis, structure and magnetic properties of linear heterobimetallic trinuclear Mn2Ln (Ln = Eu, Gd, Dy) complexes

The reaction of (S)P[N(CH(3))N[double bond, length as m-dash]CH-C(6)H(3)-2-OH-3-OCH(3)](3) with a Mn(II) salt followed by a Ln(III) salt (Ln = Eu, Gd and Dy), afforded linear heterometallic complexes [L(2)Mn(2)Ln](+) that showed interesting magnetic properties.     

Characteristic features of the nanocrystalline structure formation in Ln2Hf2O7 (Ln = Gd, Dy) compounds

A combination of modern locally sensitive methods of structure analysis based on the interaction of synchrotron radiation with condensed matter was used to study the formation and evolution of crystal structures, change in the size of crystallites, the type and degree of cationic ordering, and features of the local atomic structures of compounds Ln₂Hf₂O₇ (Ln = Gd, Dy) prepared by heat treatment of X-ray amorphous precursors.