Comparative Structural and Electrical Studies of V2O3 and V2—xNixO3 (0 < x < 0.75) Solid Solution

V₂O₃ room and low temperature structures have been refined using PXRD and Rietveld procedures. At 15 K, in addition to the umbrella like opening of V—O bonds associated to the typical large V—V distance through the face shared octahedra (V—V_fsh) we have observed three different V—V distances through the edge shared octahedra (V—V_edsh) : 2.985Å, 2.908Å, and 2.847Å. This splitting is a consequence of the rotation of V—V pairs in a plane itself rotated out of the ( ac ) one which appears to be the origin for the well‐known rhombohedral to monoclinic distortion. Ni for V substitutions drive to a V_2—xNi_xO₃ solid solution with a wide homogeneity range (0 < x < 0.75). Structure refinements on selected compositions show that at both room and 15 K temperatures the typical V₂O₃ corundum type is kept. At 300 K, the main Ni effect is a drastic decrease of the c parameter associated to a flattening of the octahedra but also to an increase of the M—M_fsh distance without rotation of the M—M pairs. This explains the absence of the monoclinic transition in the whole homogeneity and temperature ranges and shows clearly that a large M—M_fsh distance is not necessarily associated with the monoclinic form. Despite this large distance observed in the whole temperature range, the electric behavior exhibits a conductor to insulator transition. It is explained in terms of semi conduction via an electron hopping process between V³⁺ and V⁴⁺ cations which depends on Ni amounts. This last result implies also that a large M—M_fsh distance is not associated with an insulating behavior.     

ChemInform Abstract: Valence Changes of Manganese and Structural Phase Transitions in Sr1‐xPrxMnO3 (0.1 ≤ x ≤ 0.6).

Fifteen perovskite manganites Sr_1‐xPr_xMnO₃ with x = 0.1—0.6 in steps of 0.025 are prepared by solid state methods and their crystal structures are determined by synchrotron powder XRD.     

New Process of Preparation,X‐Ray Characterization,Structure and Vibrational Studies of a Solid Solution LiTiOAs1‐xPxO4 (0 ≤ x ≤ 1).

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

Fe x Ti1−2x M x O2 (M=Nb,Ta) rutile solid solutions from gels

In this study, Fe _x Ti_1–2x M _x O₂ (M=Nb, Ta) rutile solid solutions have been synthesized from gels made from Fe(III) acetylacetonate, NbCl₅, TaCl₅, Ta(V) ethoxide, TiCl₄ and Ti(IV) isopropoxide. The results obtained are compared with those obtained by the ceramic method. The solid solutions synthesized from gels were obtained at lower temperatures than these synthesized by the ceramic method.     

Superior Na‐Storage Performance of Low‐Temperature‐Synthesized Na3(VO1−xPO4)2F1+2x (0≤x≤1) Nanoparticles for Na‐Ion Batteries

Na‐ion batteries are becoming comparable to Li‐ion batteries because of their similar chemical characteristics and abundant sources of sodium. However, the materials production should be cost‐effective in order to meet the demand for large‐scale application. Here, a series of nanosized high‐performance cathode materials, Na₃(VO_1?xPO₄)₂F_1+2x (0≤x≤1), has been synthesized by a solvothermal low‐temperature (60–120 °C) strategy without the use of organic ligands or surfactants. The as‐synthesized Na₃(VOPO₄)₂F nanoparticles show the best Na‐storage performance reported so far in terms of both high rate capability (up to 10 C rate) and long cycle stability over 1200 cycles. To the best of our knowledge, the current developed synthetic strategy for Na₃(VO_1?xPO₄)₂F_1+2x is by far one of the least expensive and energy‐consuming methods, much superior to the conventional high‐temperature solid‐state method.     

Synthesis,structure, and X-ray absorption spectra of LixNbO2 and NaxNbO2 (x ≤ 1)

The two series of compounds, Li_xNbO₂ and Na_xNbO₂, were synthesized from LiNbO₂ and NaNbO₂ with oxidizing agents. From neutron diffraction, it is concluded that the Li position is fully occupied for x = 1. Even though the long-range crystal symmetry does not seem to change for x < 1, as monitored by Guinier X-ray powder patterns, the Nb? L_III XANES spectra exhibit significant spectral variations with x which reflect changes in the unoccupied d-density of states.     

Das erste KEGGIN-Anion mit tetraedrischer. Kupfer(II)—Sauerstoff-Koordination: [α-Cu0,4(H2)0,6O4W12O36]6−

The First KEGGIN-Anion with Tetrahedral Coordination of Copper(II)-Oxygen: [α-Cu_0,4(H₂)_0.6O₄W₁₂O₃₆]^6? The solution of the Cu^II-containing heteropolyanion was prepared starting from an aqueous solution of Na₂WO₄, adjusting to pH 5–6 by adding slowly a solution of Cu(NO₃)₂ in HNO₃. The addition of the corresponding amount of N(CH₃)₄Br to the concentrated solution led to the crystallization of the greenish-yellow mixed crystals (TMA)₆[α-Cu_0.4(H₂)_0.6O₄W₁₂O₃₆] · 9 H₂O. After repeated recrystallization it has been investigated by chemical, spectroscopic (IR/Raman, UV, ¹⁸³W/¹H-NMR, ESR) and X-ray diffraction methods (monoclinic; space group P2₁; a = 13.117(4), b = 21.466(4), c = 13.223(3) Å, β = 91.60°; Z = 2; D_c = 3.041 g · cm^?3; R = 8.0%). The distances of the four “tetrahedral” oxygen atoms to the position (0, 0, 0) range from 1.67 to 1.93 Å. The alternative occupation of the central KEGGIN position with copper(II) and two protons, respectively, accounts for the different distances. The prepared solid solution represents the first example for the tetrahedral copper(II)-oxygen coordination in any heteropolyanion compound.     

Novel Derivatives of the CaIn2 Type of Structure: Yb1+xMg1—xGa4 (0 ≤ x ≤ 0.058) and YLiGa4

The compounds Yb_1+xMg_1—xGa₄ (0 ≤ x ≤ 0.058) and YLiGa₄ were synthesized by direct reaction of the elements in sealed niobium crucibles. The atomic arrangement of Yb_1+xMg_1—xGa₄ (x = 0.058) represents a new structure type (space group P6¯m2, a = 4.3979(3)Å and c = 6.9671(7)Å) as evidenced by single crystal structure analysis and can be described as an ordered variant of CaIn₂. YLiGa₄ is isotypic to the ytterbium compound according to X‐ray Guinier powder data (a = 4.3168(1)Å and c = 6.8716(2)Å). Measurements of the magnetic susceptibility of both compounds reveal intrinsic diamagnetic behaviour, i.e., ytterbium in the 4f¹⁴ configuration for Yb_1+xMg_1—xGa₄ (x = 0). From electrical resistivity data both compounds can be classified as metals. The compressibility of Yb_1+xMg_1—xGa₄ (x = 0.058) as measured in diamond anvil cells by angle‐dispersive X‐ray diffraction is compatible with a valence change of the ytterbium atoms at high‐pressures and indicates a slight anisotropy which is in accordance with the structural organisation of the gallium network. X‐ray absorption spectra of the Yb L_III edge of Yb_1+xMg_1—xGa₄ (x = 0.058) at pressures up to 25.0 GPa show a two‐peak structure which reveals the presence of Yb in the 4f¹⁴ and 4f¹³ states. The amount of ytterbium in the 4f¹³ state increases in two steps with progressing compression. The bonding analysis by means of the electron localization function reveals the Zintl‐like character of both compounds and confirms the 4f¹⁴ state for the majority of ytterbium atoms.     

Molekülstrukturen von Kupfer(II)- und Eisen(III)-Chlorokomplexen mit di- und monoprotoniertem N-(Pyrid-2-ylmethyl)ethylendiamin-N,N′,N′-triacetat (H2pedta−; Hpedta2−)

Molecular Structures of Copper(II) and Iron(III) Chloro Complexes with di- and monoprotonated N-(pyrid-2-ylmethyl)ethylenediamine-N,N′,N′-triacetate (H₂pedta^?; Hpedta^2?) The molecular structures of two complexes of di- and monoprotonated N-(pyrid-2-ylmethyl)ethylenediamine-N,N′,N′ -triacetate (pedta^3?) with Cu^II and Fe^III as central atoms have been determined by single crystal X-ray diffraction methods. Both complexes have a distorted octahedral coordination with H₂pedta^? and Hpedta^2? as pentadentate ligands and a chloride ion occupying the sixth coordination site. The different oxidation states of the central atoms result in a completely different coordination behaviour of the carboxyl groups. In both complexes one of the ? CH₂? COOH groups is uncoordinated. In the Fe^III complex, the central atom is coordinated by the hydroxylic O atoms of the deprotonated carboxyl groups. Contrary to this in the Cu^II complex, the central atom is coordinated by the carbonylic O atoms. One of the coordinated carboxyl groups is protonated and the other is deprotonated. All protonated carboxyl groups in both complexes form intermolecular hydrogen bonds.     

Darstellung und Eigenschaften von tetragonalen α-Di(phthalocyaninato(1−))-praseodym(III)-polyhalogeniden; Kristallstruktur von α-[Pr(Pc−)2]Br1,5

Preparation and Properties of Tetragonal α-Di(phthalocyaninato(1?))praseodymium(III)-polyhalides; Crystal Structure of α-[Pr(Pc^?)₂]Br_1.5 Brown red di(phthalocyaninato(1?))-praseodym(III)-polyhalides [Pr(Pc^?)₂]X_y (X = Br, I) of variable composition (1 ≤ y ≤ 2.5) are formed by (electro)chemical oxidation of [Pr(Pc^2?)₂]^?. The thermical decomposition of these polyhalides at 250°C yields partially oxidized, green α-[PrPc^?Pc^2?]. Due to strong spin–spin coupling of the phthalocyanin-π-radicals only Pr^III contributes to the magnetic moment of ca. 3.0 B.M. for all complexes. Green metallic prisms of [Pr(Pc^?)₂]Br_1.5 crystallize in the tetragonal α-modification: space group P4/nnc with a = 19.634(5) Å, c = 6.485(2) Å; Z = 2. In the sandwich complex Pr^III is eightfold coordinated by the isoindoline N-atoms of the two staggered (41°), nearly planar Pc^?- ligands. The quasi-onedimensional character of the structure along [001] is due to the infinite columns of Pc^? ligands. The superperiod along [001] is a consequence of the distribution of the Pr atoms onto two incompletely filled crystallographic positions at a distance of c/2 and the disordered chains of the bromine atoms extending in the same direction. Powder diffractograms of Pr(Pc )₂Br2, [Pr(Pc^?)₂]I₂ und [PrPc Pc^2?] confirm the tetragonal α-modification of these complexes, too. The content of tribromide correlates with the population of the Pr(2)-site. In the UV-VIS-NTR absorption spectrum of a thin film of Pr(Pc )₂Br, the intense bands at 13.9 and 19.5 kK are assigned to the B and Q transition, respectively. The D band at 9. kK is characteristic for isolated dimeric Pc^?-π-radicals. Due to increasing electron delocalisation as a result of the growing columns the D band is shifted to lower energy appearing successively at 6.05 and 3.3 kK. The mir and resonance Raman (RR) spectra of α-[Pr(Pr^?)₂]X_y, (X = Br, I) show the well known diagnostic bands for Pc^?-π-radicals. Thc RR spectrum of the polyiodide is dominated by the overtone progression of the totally symmetric (I-I) stretching vibration of the triiodide at 108cm^?1. The FT-Raman spectra are also marked by the totally symmetric stretching vibration of the polyhalides (Br₃ : 145cm ¹; 1₃^?:105cm^?1; I₅^? 151 cm^?1).     

Zur Kristallstruktur von La[AuF4]3, dem Anfangsglied der Reihe M[AuF4]3−xFx (x = 0, 0,5 und 1)

On the Crystal Structure of La[AuF₄]₃, the Final Link in the Series M[AuF₄]_3?xF_x (x = 0, 0.5 and 1) Yellow La(AuF₄)₃ was prepared for the first time in form of single crystals and investigated by X-ray methods. It crystallizes in space group R3 c-D (Nr. 167) with a = 1056.2(2) pm, c = 1633.7(8) pm, Z = 6.     

Crystal structure and photoluminescence properties of a new monomeric copper(II) complex: bis(3‐{[(3‐hydroxypropyl)imino]methyl}‐4‐nitrophenolato‐κ3O,N,O′)copper(II)

Copper(II)–Schiff base complexes have attracted extensive interest due to their structural, electronic, magnetic and luminescence properties. The title novel monomeric Cu^II complex, [Cu(C₁₀H₁₁N₂O₄)₂], has been synthesized by the reaction of 3‐{[(3‐hydroxypropyl)imino]methyl}‐4‐nitrophenol (H₂L ) and copper(II) acetate monohydrate in methanol, and was characterized by elemental analysis, UV and IR spectroscopies, single‐crystal X‐ray diffraction analysis and a photoluminescence study. The Cu^II atom is located on a centre of inversion and is coordinated by two imine N atoms, two phenoxy O atoms in a mutual trans disposition and two hydroxy O atoms in axial positions, forming an elongated octahedral geometry. In the crystal, intermolecular O—H…O hydrogen bonds link the molecules to form a one‐dimensional chain structure and π–π contacts also connect the molecules to form a three‐dimensional structure. The solid‐state photoluminescence properties of the complex and free H₂L have been investigated at room temperature in the visible region. When the complex and H₂L are excited under UV light at 349 nm, the complex displays a strong green emission at 520 nm and H₂L displays a blue emission at 480 nm.     

Influence des Liaisons Chimiques sur la Transition Spin Faible → Spin Fort du Cobalt(III) (3d6) au sein D′Oxydes de Type K2NiF4

Influence of the Chemical Bonding on the Low Spin → High Spin Transition of Cobalt(III) in Oxides of the K₂NiF₄ Type It appears from a wide investigation of the LS → HS transition of cobalt(III) based on a Slichter and Drickamer model that in an oxide lattice with K₂NiF₄-type structure, the influence of the cation size in C.N.9 sites is prevailing on that resulting from the competing bonds in the pervoskite-type layers.     

Reaktion von cyclopentadienyl-substituierten Molybdän(V)-tetrachloriden mit LiPH(2,4,6-BuC6H2) und KPPh2(Dioxan)2. Molekülstrukturen von [Cp0Mo(μ-Cl)2]2 und [CpMo2(μ-Cl)3(μ-PPh2)] (Cp0 = C5Me4Et)

Reaction of Cyclopentadienyl Substituted Molybdenum(V) Tetrachlorides with LiPH(2,4,6-Bu C₆H₂) and KPPh₂(Dioxane)₂. Crystal Structures of [Cp⁰Mo(μ? Cl)₂]₂ and [Cp Mo₂(μ? Cl)₃(μ? PPh₂)] (Cp⁰ = C₅Me₄Et) The reaction of [Cp⁰Mo(CO)₃]₂ (Cp⁰ = C₅Me₄Et) and [Cp′Mo(CO)₃]₂ (Cp′ = C₅H₄Me) with PCl₅ in CH₃CN furnishes the Mo(V) complexes Cp⁰MoCl₄(CH₃CN) 1 and Cp′MoCl₄(CH₃CN) 2 in good yields. While 1 and 2 are reduced by LiPH(2,4,6-BuC₆H₂) to the Mo(III) complexes [Cp⁰Mo(μ? Cl)₂]₂ 3 and [Cp′Mo(μ? Cl)₂]₂ 4 , the reaction of 1 with KPPh₂(dioxane)₂ yields the reduction/substitution product [CpMo₂(μ? Cl)₃(μ? PPh)] 5 in low yield. 1 – 4 were characterized spectroscopically (i.r., mass, 3 and 4 also n.m.r.). An X-ray crystal structure determination was carried out on 3 and 5. 3 crystallizes in the triclinic space group P1 (No. 2) with a = 8.278(4), b = 12.508(7), c = 12.826(7) Å, α = 86.78(5), β = 81.55(2), γ = 75.65(4)°, V = 1 272.4 ų and two formula units in the unit cell (data collection at ? 67°C, 4 255 independent observed reflections, R = 2.9%); 5 crystallizes in the triclinic space group P1 (No. 2) with a = 11.536(8), b = 12.307(9), c = 13.157(9) Å, α = 91.41(6), β = 100.42(5), γ = 112.26(6)°, V = 1 688.7 ų and two formula units in the unit cell (data collection at ? 60°C, 6 147 independent observed reflections, R = 4.9%). The crystal structure of 3 shows the presence of centrosymmetric dimeric molecules with four bridging chloro ligands. In 5, two Mo atoms are bridged by three chloro ligands and one PPh₂ ligand. The Mo? Mo bond length in 3 and 5 (2.600(2), 2.596(2) Å and 2.6388(8) Å) is in agreement with a Mo? Mo bond.     

Ein alternativer Weg zur Darstellung von Bi2Sr2CaCu2Ox,YBa2Cu3O7−δ, und YBa2Cu3−xMxO7−δ (M  Ni,Ag und x ≤ 33 Mol%)

An Alternative Method for Preparation of Bi₂Sr₂CaCu₃O_x, YBa₂Cu₃O_7?δ, and YBa₂Cu_3?xM_xO_7?δ (M ? Ni, Ag and x ≤ 33 Mol%) Oxidation of quenched melts of metals in a well defined argon/oxygen atmosphere has been found as an alternative method to prepare hight purity samples of Bi₂Sr₂CaCu₂O_x without Pb-stabilization. A special equipment for the oxidation of powder samples will be described. By our new method it is also possible to prepare YBa₂Cu₃O_7?δ and derivatives of this compound, where Cu is substituted by high amounts of Ni or Ag.     

The influence of P/As substitution in the melilite‐like Na2Co(P2–xAsx)O7 (x = 0.40 and 0.93) solid solutions

To investigate the influence of P/As substitution on structures and electrical properties, e.g. the effect on material densities, two new solid P/As‐doped solutions, Na₂CoP_1.60As_0.40O₇ (disodium cobalt diphosphorus arsenic heptaoxide) and Na₂CoP_1.07As_0.93O₇ (disodium cobalt phosphorus arsenic heptaoxide), with melilite‐like structures have been synthesized by solid‐state reactions. Their unit‐cell parameters are in agreement with Vegard's law. The obtained structural models were investigated by the bond valence sum (BVS) and charge distribution (CHARDI) validation tools and, for the latter, the structures are described as being built on anion‐centred polyhedra. The frameworks can be described as layered and formed by {[Co(P,As)₂O₇]²⁻}_∞ slabs, with alkali cations sandwiched between the layers and with the interlayer spaces increased due to P/As substitution. The BVS model was extended to a preliminary simulation of the sodium conduction properties in the studied structural type and suggests that the most probable sodium conduction pathways are bidimensional, at the (002) planes.     

Origin and Location of Electrons and Protons during the Formation of Intermetalloid Clusters [Sm@Ga3−xH3−2xBi10+x]3− (x=0, 1)

Reaction of [GaBi₃]^2? with [Sm(C₅Me₄H)₃] yielded the first protonated ternary intermetalloid clusters [Sm@Ga_3?xH_3?2xBi_10+x]^3? ( 1 ; x=0,1). The presence of the Ga? H bonds and the transfer of electrons and protons during the formation of 1 were elucidated by a combination of experimental and quantum chemical methods, thereby rationalizing the role of the solvent ethane‐1,2‐diamine as a Brønsted acid. As an organic by‐product, we observed the previously unknown octamethylfulvene ( 2 ) upon C? C coupling of (C₅Me₄H)^?.     

Synthesis and magnetic properties of μ-phenolato copper (Ⅱ) binuclear complexes with different exogenous bridges

The syntheses and magnetic properties are reported for a series of copper(Ⅱ) complexes prepared from a pentadentate binucleating ligand 2,6-diformyl-4-methylphenol di(benzoyl-hydrazone) (H3L). These complexes incorporate different exogenous ions (X-) into a bridging position to form copper(Ⅱ) binuclear complexes of the formula [Cu2(H2L)X]2+, where X-= Br-(1), Cl-(2), HO-(3), C2H5O-(4) and C3H3N2- (5). The complexes have been characterized with variable temperature magnetic susceptibility (4.2-300 K) and the observed data were fit to those from a modified Bleaney-Bowers equation by least-squares method, giving the exchange integral 2J = -6.2 cm-1 for 1, -76.4 cm-1 for 2, -241.9 cm-1 for 3, -231.1 cm-1 for 4 and -343.8 cm-1 for 5. This suggested that there is an antiferromagnetic interaction between the Cu(Ⅱ) ions and the sequence of the effect of some exogenous bridging ligands on magnetic coupling is corresponding to that in spectrochemical series.