Determination of Y,Ba, Cu and O in superconductors by 14-MeV neutron activation

The possibility of using 14 MeV neutron activation for rapid, nondestructive elemental analysis of high T_c superconductors is considered. A method was elaborated and applied for investigating Y–Ba–Cu–O samples with different oxygen content. Derived from the measurements of a typical sample the uncertainty of the elemental concentrations, including oxygen, is not more than 1. 1%.     

Enthalpies of formation of some phases present in the Y−Ba−Cu−O system by solution calorimetry

Enthalpies of some of the phases in the Y–Ba–Cu–O system were determined by solution calorimetry using a Calvet microcalorimeter. The standard enthalpies of formation for the phases were found to be YBa₂Cu₃O_6.60, –2627.9; YBa₂Cu₃O_6.77, –2641.8; YBa₂Cu₃O_6.90, –2652.0; YBa₂Cu₃O_6.99, –2659.3; Y₂Cu₂O₅, –2198.6; Y₂BaCuO₅, –2656.4; BaCuO_2.33, –788.6; and BaCuO_2.42, –796.2 kJ-mol^–1.     

Mixed Complex Salt [Cu4(SCN2H4)7(NO3)](NO3)(SO4) · 3.3H2O: Synthesis and X-Ray Diffraction Analysis

The complex salt [Cu₄(SCN₂H₄)₇(NO₃)](NO₃)(SO₄) · 3.3H₂O was synthesized via reaction of aqueous solutions of thiourea with copper nitrate at 80°C and studied using X-ray diffraction analysis. The conditions and reasons for the partial oxidation of thiourea to sulfate ions were established. The crystals are monoclinic: a = 12.6072(7) Å, b = 15.4265(8) Å, c = 22.108(1) Å, = 120.133(6)°, space group P2₁/c, Z = 4. The crystal structure consists of [Cu₄(SCN₂H₄)₇(NO₃)]³⁺ complex cations, SO₄ ^2–, and NO₃ ^– anions, and molecules of the water of crystallization. Three types of coordination of the Cu atom were distinguished in the structure: trigonal (Cu–S 2.213–2.279 Å), tetrahedral (Cu–S 2.315–2.459 Å), and trigonal–pyramidal (3+1) (Cu–S 2.26–2.288, Cu–O 2.68 Å). The NO₃ ligand was found to be orientationally disordered.     

Coordination chemistry of alkali and alkaline earth cations. Barium-crown encapsulation studies: The synthesis and crystal structure of barium(picrate)2(benzo-15-crown-5) monohydrate

The interaction of barium with benzo-15-crown-5 (B15C5) has been followed under the competitive effect of various chelating organic anions (L), nitrophenolates and nitrobenzoates, in ethanol and ethanol-water (9:1). The rather heavily hydrated BaL₂ salts yield novel 1:1 stoichiometric products in monohydrated or anhydrous states. Use of excess crown does not under any condition lead to the formation of 1:2 charge separated complexes, expected in view of the cavity and the cation sizes. The 1:1 Ba–B15C5 interaction is counteracted by L in accordance with its nucleophilicity, i.e., the pK _a value of its parent acid, HL. The complex Ba(picrate)₂(B15C5)·H₂O (BaC₂₆H₂₆N₆O₂₀, FW=879.0), is monoclinic,P2₁/c,a=11.43(1),b=16.31(3),c=17.38(2) Å, =92.265(3)°,Z=4,D _c=1.77 g/cm³,D ₀=1.73 g/cm³, MoK, =0.71069 Å, 2 (4.0–50°), =13.5 cm^–1,F(000)=1752,T=–32°C. FinalR for the 5926 reflections was 0.049. The structure reveals barium to be 10-coordinated through all the five crown oxygens (Ba–O, 2.800 to 3.002 Å), the two bidentate picrates (Ba–O, 2.642 and 2.666 Å; Ba–ONO, 2.825 and 2.994 Å), and the water molecule (2.711 Å) so that the cation constitutes a pseudo-sandwich of the crown on one side and the anionic species on the other. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82007 (50 pages). To obtain copies, see page ii of this issue.     

Molecular structure and bonding properties of tris(N-methyl-formamide) formamide)(N,N, N', N'-tetramethylethylenediamine)-copper(II) perchlorate

Summary The x-ray crystal structure of tris(N-methylformamide) (N, N, N', N'-tetramethylethylenediamine)copper(II) perchlorate has been determined using three-dimensional x-ray diffraction data. The complex crystallizes in space group P2₁/c with Z=4. The cell dimensions are=8.255(3),b=17.951(6),c=16.541(4) Å, and =91.03(2)°. Least-squares refinement of the structure has yielded a final R value of 4.52% for 2108 independent reflect ions. The square pyramidal structure consists ofN, N, N', N'-tetramethylethylenediamine and twoN-methylformamide ligands forming a basal square plane with Cu–N bond lengths of 2.029(5) and 2.033(5) and Cu–O 1.981(4) and 1.985(4) Å, and a thirdN-methylformamide on the apex with a Cu–O distance of 2.181(4)Å. Each of the molecular plances of the three N-methylformamides lies nearly coplanar with thexy, yz andxz molecular coordination planes. The bonding properties of the title compound and its i.r. and uv-vis spectra are discussed with reference to the structure.     

Thermal and Microstructural Analysis of the Y–Ba–Cu–O/Ag Equilibrium Around the Critical Composition YBa2Cu3Ox/Ag 35 mass%

We studied the Y–Ba–Cu–O/Ag equilibrium diagram in oxygen atmosphere around the composition YBa₂Cu₃O_x/Ag35 mass%. We found a high thermal effect: the peritectic decomposition temperature of Y-123 phase is lowered from 1040 to 940°C. We demonstrate here that the nature of the phenomenon is not chemical. We explained it as the result of a mechanical segregation of Y-123 decomposition products from Y-123 phase, performed by silver. This revised version was published online in July 2006 with corrections to the Cover Date.     

Selective alcohol oxidation to aldehydes and ketones over base-promoted gold–palladium clusters as recyclable quasihomogeneous and heterogeneous metal catalysts

Bimetallic gold–palladium clusters, with an average size of 1.9 nm and composed of 80 mol% gold, proved to be highly active and selective metal catalysts for the organic phase oxidation with O₂ of aliphatic, allylic and benzylic alcohols to the corresponding carbonyl products. Polyvinylpyrrolidone stabilized gold–palladium clusters dispersed in N,N-dimethylformamide emerged as promising quasihomogeneous metal catalysts for the oxidation of benzyl alcohol to benzaldehyde with full selectivity; they could be efficiently recycled with unaffected catalytic performance by solvent-resistant nanofiltration. Highly active and durable heterogeneous catalysts for the amide phase or solvent-free alcohol oxidation were prepared by the quantitative immobilization of the optimized gold–palladium clusters on the high surface area basic BaAl₂O₄ spinel support with preservation of the bimetallic clusters’ nanodispersion.     

An approach to the structure and spectra of copper barbiturate trihydrate

In the neutral title complex [Cu(C₄N₂H₃)₂(H₂O)₃] or [Cu(BBR)₂(H₂O)₃] (BBR^– = Barbiturate), the Cu^II ion, in the slightly distorted square-pyramidal geometry, is coordinated by two O atoms of the two monodentate barbiturates and three O atoms of three water ligands. The average bond length of Cu—O (BBR^–) is 1.981(5) Å and the average bond length of Cu—O (H₂O) at the basal sites is 1.94(5) Å, i.e. much shorter than that of Cu—O (H₂O) [2.175(11) Å]. The crystal structure is characterized by an extensive network of hydrogen bonds in which each [Cu(BBR)₂(H₂O)₃] entity links to six adjacent [Cu(BBR)₂(H₂O)₃] by O(C=O) ··· H—O(H₂O) bonds. Tautomerism in the coordination process for BBR^– was found from the crystal structure and i.r. spectral analysis. The interaction of Cu^II and BBR^– in aqueous solution was also investigated by electronic spectra and electrochemical method. It was observed that the copper ion could not only form the [Cu(BBR)₂(H₂O)₃] complex in aqueous but also catalyze the decomposition of BBR^– at pH 1.1.     

Synthesis and crystal structure analysis of Sr8Cu3In4N5 and Sr0.53Ba0.47CuN

Single crystals of new quaternary compounds Sr₈Cu₃In₄N₅ and Sr_0.53Ba_0.47CuN were prepared, respectively, from a Sr–Cu–In–Na melt under 7 MPa of N₂ and from a Sr–Ba–Cu–In–Na melt under 0.5 MPa of N₂ by slow cooling from 1023 to 823 K. The crystal structures were determined by single-crystal X-ray diffraction. Sr₈Cu₃In₄N₅ has an orthorhombic structure (space group, Immm, Z=2, a=3.8161(5) Å, b=12.437(2) Å, c=18.902(2) Å), and is isostructural with Ba₈Cu₃In₄N₅. It contains nitridocuprates of isolated units ⁰[CuN₂] and one-dimensional linear chains _∝¹[CuN_2/2] and one-dimensional indium clusters _∝¹[In₂In_2/2]. Sr_0.53Ba_0.47CuN crystallizes in an orthorhombic cell, space group Pbcm, Z=4, a=5.4763(7) Å, b=9.2274(12) Å, c=9.0772(12) Å. The structure contains infinite zig-zag chains _∝¹[CuN_2/2] which kink at every second nitrogen atom.     

Oxidation with the H2O2—VO3 −—pyrazine-2-carboxylic acid reagent

Aromatic hydrocarbons are oxidized with hydrogen peroxide in the presence of catalytic amounts of VO₃ ^– and pyrazine-2-carboxylic acid into phenols (provided excess hydrocarbon is used) or into quinones (at high H₂O₂ concentrations). 2-Propanol, ethanol, cyclohexanol, and benzyl alcohol are transformed into the corresponding aldehydes and ketones under the same conditions (without a solvent or in MeCN).For part 1, see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1394–1396, August, 1993.     

Diaqua[N,N-di(2-carboxyethyl)-o-anisidinato]copper(II) Dihydrate [Cu(o-Andp)(H2O)2] · 2H2O: Synthesis and Crystal Structure

Crystals of [Cu(o-Andp)(H₂O)₂] · 2H₂O (where o-Andp^2–is -anisidine-N,N-di-3-propionate) were synthesized and studied using X-ray diffraction analysis. The crystals are triclinic: a= 12.063(1) Å, b= 12.483(3) Å, c= 13.586(2) Å, = 91.29(1)°, = 111.67(1)°, = 104.00(1)°, V= 1830.5(5) ų, space group P , Z= 2, and R= 0.0528 for 5965 reflections with I2(I). The two crystallographically independent complexes are isostructural. The tetragonal–bipyramidal coordination of copper(III) involves three O atoms, the N atom of the tetradentate ligand o-Andp^2–, and two O atoms from water. The aminodipropionate group of the ligand (average Cu–O 1.939 Å and Cu–N 2.051 Å) and one of the coordinated water molecules (Cu–O(w) 1.991 Å) lie in the equatorial plane. The second water molecule (Cu–O(w) 2.32 Å) and the methoxy O atom of o-Andp^2–(Cu–O 2.37 Å) are in the apical positions of the bipyramid.     

Bonding properties and electronic structures of glycylglycinato copper(II) complexes. Molecular structure of acetylhistaminegly-cylglycinatocopper(II) dihydrate

Summary Mixed ligand diglycinatocopper(II) complexes of the Cu(glygly)L·nH₂O type, where glygly stands for [NH₂-CH₂ CONCH₂CO₂]^2– and L for imidazole (n = 1.5), N-methylimidazole (n = 1), 2-methylimidazole (n = 2), 4-methylimidazole (n = 2), 4-phenylimidazole (n = 2), N-acetylhistamine (n = 2) and NH₃ (n = 2), were prepared and characterized by elemental analyses, i.r., vis. and e.p.r. spectroscopic measurements. The molecular structure of [Cu(glygly)(achmH)]·2H₂O (achmH = acetylhistamine) was determined using three dimensional XRD data. The structure consists of distorted square planar [Cu(glygly)-(achmH)] units interconnected via the peptide oxygen at the apex to complete a square pyramidal structure, Cu—O-(peptide) 2.477(2) Å. The H₂O molecules, not binding directly to the copper ion, involve in intermolecular hydrogen bonding with the copper units. The dianionic glygly ligand and the imidazole ring bind strongly to the central copper ion with Cu—N(amino) 2.045(6) Å, Cu—N-(peptide) 1.891(5) Å, Cu—O(carboxylate) 2.001(4) Å and Cu—N(imidazole) 1.956(5) Å. The dihedral angle between the imidazole nucleus and the CuN₃O xy plane is 6.0°. Similar structures with a CuN₃O coordination plane are proposed for the imidazole complexes, based on spectroscopic data. The bonding properties of the glygly ligand and the unidentate imidazole ligands are elucidated and discussed with reference to the electronic structures of the complexes deduced from Gaussian analyses.     

Synthesis, structure and DNA binding studies of mononuclear copper(II) complexes with mixed donor macroacyclic ligands, 2,6-bis({N-[2&3-(phenylselenato)alkyl]}benzimidoyl)-4-methylphenol

Two new phenol based macroacyclic Schiff base ligands, 2,6-bis({N-[2-(phenylselenato)ethyl]}benzimidoyl)-4-methylphenol (bpebmpH, 1) and 2,6-bis({N-[3-(phenylselenato)propyl]}benzimidoyl)-4-methylphenol (bppbmpH, 2) of the Se₂N₂O type have been prepared by the condensation of 4-methyl-2,6-dibenzoylphenol (mdbpH) with the appropriate (for specific reactions) phenylselenato(alkyl)amine. These ligands with Cu(II) acetate monohydrate in a 2:1 molar ratio in methanol form complexes of the composition [(C₆H₂(O)(CH₃){(C₆H₅)CN(CH₂)_nSe(C₆H₅)}{(C₆H₅)CO}₂Cu] (3 (n = 2), 4 (n = 3)) with the loss of phenylselenato(alkyl)amine and acetic acid. In both these complexes, one arm of the ligand molecule undergoes hydrolysis, and links with Cu(II) in a bidentate (NO) fashion, as confirmed by single crystal X-ray crystallography of complex 3. The selenium atoms do not form part of the copper(II) distorted square planar coordination sphere which has a trans-CuN₂O₂ core. The average Cu–N and Cu–O distances are, respectively, 1.973(3) and 1.898(2) Å. The N–Cu–N and O–Cu–O angles are, respectively, 167.4(11)° and 164.5(12)°. The compounds 1–4 have been characterized by elemental analysis, conductivity measurements, mass spectrometry, IR, electronic, ¹H and ⁷⁷Se{¹H} NMR spectroscopy and cyclic voltammetry. The interaction of complex 3 with calf thymus DNA has been investigated by a spectrophotometric method and cyclic voltammetry.     

Isotachophoretic determination of stability constants of Ho and Y complexes with diethylenetriaminepentaacetic acid and 1,4,7,10-tetraazadodecane-N,N′,N″,N-tetraacetic acid

The method of capillary isotachophoresis with conductivity detection was applied for the determination of the physico-chemical characteristics (conditional stability constants log β′) of holmium and yttrium complexes with DTPA (diethylenetriaminepentaacetic acid) and DOTA (1,4,7,10-tetraazadodecane-N,N′,N″,N-tetraacetic acid). The log β′ determination is based on the linear relation between the stability constants of lanthanide–DTPA (lanthanide–DOTA) complexes and the reduction of the zone of the complex owing to the bleeding phenomena (liberating free metal ion). The stability constants calculated using this relationship are comparable with the literary data obtained by other methods for both holmium (log β′_Ho–DTPA=21.9, log β′_Ho–DOTA=24.5) and yttrium complexes (log β′_Y–DTPA=21.2, log β′_Y–DOTA=24.4). Capillary isotachophoresis was applied for the determination of the optimum composition of the reaction mixture (metal:ligand ratio) as well.     

Coordination Compounds of Copper(II) Nitrate with Products of Aminotris(hydroxymethyl)methane Condensation with Salicyl- and 5-Nitrosalicylaldehydes: Synthesis and Crystal Structures

The crystal structures of copper(II) nitrate complexes with 2-(2-hydroxybenzylideneamino)-2-hydroxymethylpropane-1,3-diol (HL) and 2-hydroxymethyl-2-(2-hydroxy-5-nitrobenzylideneamino)propane-1,3-diol (HL¹) were determined. The resulting complexes were formulated as [Cu₃OL₃(H₂O₂]NO₃ · 3H₂O (I) and [Cu(H₂O)L¹]NO₃ (II). The crystals of I are monoclinic, a = 17.809(4) Å, b = 30.549(6) Å, c = 18.962(4) Å, β = 115.36(3)°, space group Cc, Z = 8, R = 0.0482. Complex I is composed of two independent three-dimensional µ₃-oxo complexes; the coordination polyhedron of the copper atoms in both compounds is an elongated tetragonal bipyramid. The coordination polyhedron of the third Cu atom is a tetragonal pyramid. The bases of the pyramids are composed of the oxygen atoms of the phenol and alcohol OH groups, the imine N atom of ligand L, and µ ₃-oxo atoms. The phenol and water O atoms serve as the apices in both the tetragonal bipyramids. The crystals of II are triclinic, a = 6.062(1) Å, b = 7.701(2) Å, c = 16.162(3) Å, α = 88.15(3)°, β = 84.94(3)°, γ = 78.13(3)°, space group P1¯, Z = 2, R = 0.0272. Complex II is composed of polymer chains formed by coordination bonds between the copper atom and two O atoms of the amino alcohol in the azomethine of the neighboring complex connected to the initial one by translation along the x axis. These chains are linked through hydrogen bonds involving the oxygen atoms of the NO₂ groups. The benzene rings of the azomethine ligands of the adjoining complexes from different chains are antiparallel to each other. The coordination polyhedron of the central atom is an elongated tetragonal bipyramid. Its equatorial plane is formed by the phenol O atom, one of the alcohol O atoms, the N atom of ligand L¹, and the O atom of the amino alcohol in the neighboring complex. The apices are the O atom of the water molecule and the O atom of the amino alcohol in the neighboring azomethine molecule. In complexes I and II, the outer-sphere nitrato group mainly serves to unite trimers and polymers in the crystal by means of hydrogen bonds.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 621–629.Original Russian Text Copyright © 2005 by Chumakov, Tsapkov, Simonov, Antosyak, Bocelli, Perrin, Starikova, Samus, Gulea.     

Holey Lamellar High-Entropy Oxide as an Ultra-High-Activity Heterogeneous Catalyst for Solvent-free Aerobic Oxidation of Benzyl Alcohol

The development of noble-metal-free heterogeneous catalysts is promising for selective oxidation of aromatic alcohols; however, the relatively low conversion of non-noble metal catalysts under solvent-free atmospheric conditions hinders their industrial application. Now, a holey lamellar high entropy oxide (HEO) Co_0.2Ni_0.2Cu_0.2Mg_0.2Zn_0.2O material with mesoporous structure is prepared by an anchoring and merging process. The HEO has ultra-high catalytic activity for the solvent-free aerobic oxidation of benzyl alcohol. Up to 98 % conversion can be achieved in only 2 h, to our knowledge, the highest conversion of benzyl alcohol by oxidation to date. By regulating the catalytic reaction parameters, benzoic acid or benzaldehyde can be selectively optimized as the main product. Analytical characterizations and calculations provide a deeper insight into the catalysis mechanism, revealing abundant oxygen vacancies and holey lamellar framework contribute to the ultra-high catalytic activity.     

Heterogeneous catalytic transformation of isobutyl benzoate by the inverse Tishchenko reaction

Using the catalytic transformation of isobutyl benzoate at 663 K in the presence of 12 % MnO₂/-Al₂O₃ in a He atmosphere as an example, it has been shown that the inverse Tishchenko reaction can take place at a temperature above 600 K. Isobutyl benzoate gives isobutanal and benzaldehyde as well as products of their transformation,i.e., benzyl isobutyrate, isobutanol, benzyl alcohol, and toluene.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1494–1496, August, 1994.     

Molecular structure and bonding properties of bis(1-methylimidazole)bis(perchlorato)bis(pyridineN-oxide)copper(II)

Summary The crystal and molecular structure of bis(1-methylimidazole)bis(perchlorato)bis(pyridineN-oxide)copper(II) have been determined using three-dimensional x-ray diffraction data. The complex crystallizes in space group P2₁/c with Z=2. The cell dimensions area=9.355(3),b=14.363(4),c=9.698(4) Å, and =106.40(3)^o. Least-squares refinement of the structure has yielded a final R value of 0.049 for 1235 independent reflections. The centrosymmetric structure consists oftrans pairs of 1-methylimidazole and pyridineN-oxide figands forming a square planar geometry with Cu–N and Cu–O bond lengths of 1.963(4) Å and 1.948(4) Å, respectively. The two perchlorate ions are located above and below the square plane with Cu–O distances of 2.590(5) Å. The uv-vis and i.r. spectra and bonding properties of the title compound are discussed with reference to the structure.     

Phasen mit Diamant-Unterstruktur in ternären Beryllium-Legierungen

Zusammenfassung In den Systemen Be–Cu–Mg, Be–Cu–Al, Be–Cu–Si, Be–Cu–Zn, Be–Cu–Ge, Be–Cu–In wurden ternäreLaves-phasen mit dem kubischen Cu₂Mg-Strukturtyp gefunden. Der Dreistoff Be–Co–Si zeigt eine ternäre Phase mit Cl- oder B32-Typ.

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In the systems Be–Cu–Mg, Be–Cu–Al, Be–Cu–Si, Be–Cu–Zn, Be–Cu–Ge, Be–Cu–In ternaryLaves phases with the cubic Cu₂Mg structure are found. The ternary system Be–Co–Si shows a ternary phase with the C1 or B32 type.

     

Crystal and molecular structures of heteroligand bis(hexafluoroacetylacetonato)copper(II) complexes with 3-imidazoline nitroxyl radicals,Cu(C5HF6O2)2:L=1:1 (L1=C13H18N3O,L2=C8H15N2O)

Crystal structures were determined for two new derivatives of heteroligand complexes of Cu(C₅HF₆O₂)₂ with nitroxyl radicals derived from 3-imidazoline: Cu(C₅HF₆O₂)₂(C₁₃H₁₈N₃O) (I) and Cu(C₅HF₆O₂)₂(C₈H₁₅N₂O) (II). The unit cell parameters for I are as follows: a=10.555(3), b=15.505(5), c=18.509(6) Å, V = 3029(1) ų, Z=4, d_calc=1.57 g/cm³, space group P2₁2₁2₁. The unit cell parameters for II are as follows: a=16.018(3), b=15.886(3), c=19.665(4) Å, V = 5004(1)ų, Z=8, d_calc=1.68 g/cm³, d_exp=1.68 g/cm³, space group P2₁2₁2₁. The structure of I is molecular. The coordination of the copper ion is a trigonal bipyramid formed by two oxygen atoms of the (hfac) ions and the nitrogen atom of the imidazoline heterocycle in the equatorial plane [Cu–O, 1.91(7), 2.242(7) Å, Cu–N, 2.010(7) Å] and the other oxygen atoms of the (hfac) anion in the axial positions [Cu–O, 1.940(6), 1.963(6) Å]. Complex II is polymeric. The two crystallographically independent Cu(hfac)₂ fragments are linked in a chain by means of two L² ligands. The coordination of the copper ions is a square bipyramid, whose equatorial plane is formed by the oxygen atoms of the (hfac) anion [Cu–O, 1.89(1)–2.03(1) Å]. The axial positions are occupied by nitrogen atoms [Cu–N, 2.52(1), 2.40(1) Å] and an oxygen atom of the NO fragment [Cu–O, 2.96(1), 2.67(1) Å] of different L² ligands. The ...Cu(hfac)₂–L²–Cu(hfac)₂–L₂... chains in the unit cell are located at two levels (x1/4 and 3/4).Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 2, pp. 126–133, March–April, 1993.