Resistive and Magnetic Susceptibility Transitions in Superconducting (TMTSF)2C104

We report measurements of the ac magnetic susceptibility and dc resistive superconducting transitions in the organic superconductor (TMTSF)₂C10₄. Inductive measurements show complete diamagnetic shielding below a broad transition and initial flux penetration at very low fields [H_c1(0) < 1 Oe]. The resistive transition is also broad, but occurs at a significantly higher temperature than the inductive transition, T_c = 1.0 K and 0.65 K respectively. Resistance measurements also show evidence of a phase transition in the vicinity of 24 K. Magnetic field induced transitions, measured both inductively and resistively, show marked anistropy both in magnitude and in breadth of the transition. Results suggest that (TMTSF)₂C10₄ is a quasi ID or 2D superconductor at high temperatures and high magnetic fields and an anisotropic bulk superconductor at low temperatures and fields. Associated thermoelectric power measurements suggest that spin density waves coexist with the superconducting state.     

Magnetotransport In (TMTSF)2PF6 and (TMTSF)2C104 Under Pressure

We have shown from the magnetotransport that the Fermi surface of (TMTSF)₂PF₆ is effectively closed two-dimensionally and is compensated in the metallic state at low temperature. These results are inconsistent with a broad regime of one-dimensional superconducting fluctuations.

Independent electron theory is seen to be inadequate to explain either the Fermi surface or the threshold field for oscillations, thereby implying that correlation effects are still important in the metallic state. Finally, an anomaly has been observed in the magnetotransport of (TMTSF)₂C10₄ which is analogous to the threshold field in (TMTSF)₂PF₆.     

Structure oftrans-difluorobis(1,3-propanediamine)chromium(III) perchlorate,trans-[Cr(N2C3H10)2F2](C104)

The title compound is monoclinic,M _r =337.8,P2₁/c-C _2h ⁵ (No. 14),a=5.508(2),b=13.944(6),c=18.238(5) Å,=95.99(3)°,V=1393.1(9) ų,Z=4,D _x =1.61 g cm^–3, (MoK)=0.71073 Å,F(000)=660.0,=10.3 cm^–1, finalR=0.051 for 2122 observed [I>3(I)] reflections. The two six-membered rings resulting from the coordination of the 1,3-propanediamine ligands to the chromium atom are in the chair conformation. The Cr-N and Cr-F distances average 2.085(4) and 1.876(3) Å, respectively.     

One Dimensional Organic Superconductivity in (TMTSF)2PF6 and (TMTSF)2C104 Detected Via Tunnel Spectroscopy

Electron tunnelling data in (TMTSF)₂ X-GaSb Schottky barriers support the idea that strong superconducting fluctuations exist in quasi-one-dimensional (TMTSF)₂X up to temperatures which are about one order or magnitude higher than the 3-D ordering critical temperature. Other tunnelling data tend to indicate that stabilization of superconductivity is possible at high temperature via chain cross-linking.     

Crystal structures of mixed compounds Cu(2)Gly(D-Ser)(L-Ser)2 and Cu(2)Gly 3(L-Ser)

-The crystal structures of mixed coordination compounds, Cu(2)Gly(D-Ser)(L-Ser)₂(I) and Cu(2)Gly ₃(L-Ser)(II), which contain the amino acid residues of glycine (Gly) and serine (Ser) in the 1: 3 and 3: 1 ratio, respectively, are studied by electron diffraction. Crystals I and II are triclinic, Z = 1, and space group P1. For I, a = 8.96(2) Å, b = 9.66(2) Å, c = 5.07(2) Å, α = β = 90°, and γ = 92.8(3)°. For II, a = 8.37(2) Å, b = 9.65(2) Å, c = 5.06(2) Å, α = β = 90°, and γ = 92.8(3)°. Compounds I and II have layered structures that are based on the CuGly(L-Ser) fragment. Structures I and II differ mainly in their interlayer spacing and configuration of the interlayer space.     

Synthesis and Structure Study of the Complex [Cu2 (μ–C2O4) (C10H8N2)2(H2O)2] (C6H4COSO2N)2 Crystal Structure Containing Cu (II) Bipy Oxalato and Saccharin

The title compound has been synthesized and its crystal structure determined at room temperature. MW = 927.86, monoclinic, space group P2₁/c, Z = 2, a = 9.283(1) Å, b = 16.239(2) Å, c = 12.209(1) Å, β = 99.848(9)°. The crystal structure consists of repeated [Cu₂(μ–C₂O₄)(C₁₀H₈N₂)₂ · (H₂O)₂]₂ cations and non-coordinated saccharin anions. Each copper ion is in a square pyrimidal environment with two oxalate oxygen and two bipyridine nitrogen atoms as a base and one water molecule at the apex. The two copper ions are bridged by oxalato and the distance is 5.138 Å.     

双核Cu(II)-5-溴水杨醛缩氨基甲磺酸席夫碱4,4'-联吡啶三元配合物的合成及晶体结构

采用Cu(II)盐和氨基甲磺酸缩-5-溴水杨醛席夫碱(H2L)以及4,4'-联吡啶(bpy)在乙醇和水溶液中合成了三元配合物,通过元素分析、红外光谱对配合物进行了表征,并用X射线衍射测定了其结构.结构解析表明,该标题配合物属单斜晶系,空间群P21/c,晶胞参数为: a=0.9509(2) nm,b=1.8783(2) nm,c=1.0514(2) nm;β= 98.48 (1)°,V=1.8575(3) nm3, Z=2,Dc=1.812 g·cm-3, F(000)=1016, μ=3.473,最终偏差因子(对I＞2σ(I)的衍射点)R1=0.0459, wR2=0.0739,对全部衍射点R1=0.1205, wR2=0.0887, ω-1= [σ2(Fo)2+0.0345P],P=(Fo2+2Fc2)/3.邻近配合物分子间存在着大量的氢键, 席夫碱三元配合物通过氢键作用堆积成2D网状结构.     

Epitaxial growth in the (111)Ag/Cu and (111)Au/Cu systems

The initial stages of epitaxial growth in the (111)Ag/Cu and (111)Au/Cu systems were investigated using UHV-RHEED and TEM on the same specimens. Flat, monocrystalline (111)Cu substrates, 1100 Å thick, were formed in situ in the RHEED system on (111)NaCl/mica bilayers. The latter consisted of air-cleaved mica on which 150 Å of NaCl was vacuum-evaporated to form a (111)NaCl monocrystalline film. The NaCl layer allowed easy removal in water of the subsequently deposited bilayer metal film. RHEED showed that these Cu films grew with extremely flat surfaces at 400°C and 10 Å/sec deposition rates. They were then annealed at 500°C for 15 min to reduce their dislocation content and finally used as substrates for subsequent deposition of thin Ag or Au superlayers. The average Ag and Au superlayer thicknesses were varied from fractions of an Angstrom to approximately 20 Å. It was shown that despite the elongated streaks in the RHEED patterns, film growth occurred by an island mechanism, the islands having flat top surfaces. In the initial growth processes, the islands merely thickened. After a few average monolayers were deposited, the islands began to widen, often by means of much thinner islands, finally coalescing into a continuous film. The Au overgrowths became continuous in the 6–11 Å thickness range. In the case of Ag, there still were some open areas in the overgrowth at 20 Å. In both cases the continuous regions of the Ag and Au overgrowths consisted of sharply delineated thick and thin areas that gave rise to steps on the otherwise flat surface.     

A new assembly containing [Fe(dien)2]2+ and [Ni(CN)4]2− ions

A tetracyanometallate with complex dien cation [Fe(dien)₂][Ni(CN)₄] (1) (dien = diethylenetriamine), has been prepared and characterized by IR, UV-Vis and ESR spectroscopies. Single crystal X-ray analysis reveals that the compound assumes a ‘zero-dimensional’ structure in which one iron(II) ion is coordinated by six nitrogen atoms of the two dien ligands and the [Ni(CN)₄]²⁻ anion remains outside the coordination sphere. The six-coordinate iron(II) centres display a distorted octahedral arrangement.     

Crystal and molecular structure of chlorotris(triphenylarsine)Cu(1),C54H45As3CuCl

The title compound crystallizes in the monoclinic space groupP2₁/n, witha=28.494(2),b=10.148(5),c=32.172(2) Å,=94.57(1)°, andZ=8 (with two independent molecules in the asymmetric unit). The structure was solved by direct methods and refined by block-diagonal least-squares methods toR=0.057 for 12286 observed reflections. The dimensions and conformations of the two independent molecules are closely similar. The coordination around the copper and arsenic atoms is approximately tetrahedral, although distortion is considerable. Some important mean bond distances and angles with their rms standard deviations are: Cu-Cl=2.270(4), Cu-As=2.419(4), As-C=1.953(2) Å, Cl-Cu-As=105.4(1.2), and As-Cu-As=113.3(8)°.     

A mixed valence Cu(I)/Cu(II) chain compound: crystal structure of 1,4,8,11-tetraazacyclotetradecanecopper(II) tribromocuprate(I)

The essentially anaerobic reaction of CuBr₂ and 14ane-N₄ in water/acetone solvent (14ane-N₄ = 1,4,8,11-tetraazacyclotetradecane) yields a mixed valence Cu(I)/Cu(II) compound. The compound is orthorhombic, space group Pcnn, with a = 23.6310(1) Å, b = 23.6429(2) Å, c = 12.4537(1) Å and V = 6957.95(9) ų with Z = 16, for _calc = 2.349 g/cc. Refinement of a twinned crystal with 8,504 unique reflections yielded final values of R₁ = 0.0725 (|F| > 2) and w R₂ = 0.114 and a goodness of fit of 1.448. The compound contains chains of Cu(14ane-N₄)²⁺ cations and CuBr₃ ^2– anions, which are linked together by long semicoordinate Cu(II)···Br bonds. The chains run perpendicular to the c axis and are arranged in layers in which the chains alternately run parallel to the (1 1 0) and to the (1 –1 0) crystal directions. The Cu(II) ion is coordinated by the tetradentate macrocycle to yield an approximate square planar coordination. The CuBr₃ ^2– anions have a nearly trigonal planar with Cu–;Br(ave) = 2.38(1) Å.     

Dependence of photo-oxidation on Ag(Cu)-content in Ag(Cu)–As2Se3 films

We report the dependence of photo-oxidation (i.e., the formation of As₂O₃ microcrystals) on Ag (or Cu) content in Ag-doped As₂Se₃ and Cu-doped As₂Se₃ films. These chalcogenide films were prepared by thermal evaporation and photodoping, and their film surface was illuminated in air with an Ar laser beam of a wavelength of 0.5145 μm. From viewpoint of applications, we paid attention to the probability and the beginning optical intensity of the As₂O₃ microcrystals formation, and the photodarkening effect as a function of Ag (Cu) content. It has been confirmed that the addition of metals Cu or Ag into As₂Se₃ films is very useful in for suppressing or weakening such a harmful oxidation reaction. It has also been found that there is a distinct difference in these properties between Ag–As₂Se₃ and Cu–As₂Se₃ films, which is attributed to the difference in the coordinate number between Ag and Cu atoms.     

Polymeric copper(II)-orotato complexes, [(C5H2N2O4)Cu(H2O)2]n

The compound [(C₅H₂N₂O₄)Cu(H₂O)₂]_n has been synthesized and its structure determined at room temperature. The primary coordination sphere at the Cu ion is square planar with the orotate dianion coordinating at the metal through heterocyclic nitrogen atom and adjacent oxygen of the carboxylate group, the remaining coordination sites are occupied by two water molecules. The orotate dianion is tricoordinated to one copper via N₁ and one oxygen of the carboxylato group and to another copper atom via the other oxygen of the carboxylato group. The coordination at copper is extended to five by the other oxygen of the carboxylate group of another orotate molecule. Thus, the molecules are associated to form chains, the carboxylato group acting as a bridge between the metal ions, the orotato-group being tridentate. The title compound crystallizes in the monoclinic space group. P2₁/n₁ with a = 9.515(5), b = 6.925(2), c = 11.861(6) Å, = 95.285(9)°, D _calc = 2.17 g cm^–3, and z = 4.     

Crystal structure of mixed-ligand copper(II) complexes. Bis(2,2′-bipyridyl)monophenylphos-phatocopper(II)monophenylphosphate monohydrate, [Cu(C10H8N2)2(C6H5OPO3)]-(C6H5OPO3H2)(H2O)

The title mixed-ligand copper(II) complex has been synthesized and its crystal structure at room temperature solved. The crystals are monoclinic:P2₁/c,a=12.004(3),b=19.402(5),c=14.192(4) Å,=108.80(3)°,Z=4. The structure was solved by direct methods, and refined to anR value of 0.041 for 4457 nonzero independent reflections. The crystal structure consists of discrete [Cu(bipy) (MPhP)] units, noncoordinated MPhPH₂, and H₂O molecules. Each [Cu(bipy)₂(MPhP)] unit involves a five coordinate CuN₄O chromophore with a distorted trigonal-bipyramidal stereochemistry. The phosphate groups are linked together by short hydrogen bonds of (P)-O-H--O-P type.     

Crystal and molecular structure of bis[pyridine-2-(N-cyanocarboxamidato)]aquocopper(II), Cu(C5H4NCONCN)2(OH2)

Bis[pyridine-2-(N-cyanocarboxamidato)]aquocopper(II), Cu(C₅H₄NCONCN)₂(OH₂), has been prepared and its i.r. spectrum and crystal structure have been determined. The crystals are triclinic (P¯1):a = 11·45(1),b = 10·35(1),c = 7·48(1) Å, = 110·9(1), = 102·2(2), = 108·9(1)°,Z = 2. The X-ray analysis, carried out using three-dimensional Patterson, Fourier and least-squares methods (finalR = 5·7%), showed copper(II) to be pentacoordinated, with two organic ligands chelating through their pyridine [Cu-N = 1·997(4), 1·989(4) Å] and amide nitrogen atoms [Cu-N = 1·980(7), 2·006(6) Å], and with one water molecule at a distance [Cu-OH₂ = 2·335(4) Å] sensibly longer than the usual Cu-O(2·0 Å) coordinate bonds. The coordination polyhedron can be described either as a distorted tetrahedron formed by the nitrogen atoms with an extra position occupied by water or as a trigonal bipyramid having water and two nitrogen atoms in the equatorial plane. The packing determining interactions are the hydrogen bonds formed by water, and a long Cu...N (3·420 Å) contact between the metal and a nitrogen atom from an adjacent molecule.The authors are indebted to Prof. Immirzi who kindly supplied his computer programmes.     

Tetrahedral site of Fe(III) and Cu(II) in renierite

Renierite from Congo is used in the present investigations. It contains only two transition elements iron and copper. EPR results indicate the presence of Fe(III) and Cu(II) with g values 2.03 and 2.40 respectively. Optical absorption spectrum shows several energies in UV‐Vis and NIR region. These energies indicate both Fe(III) and Cu(II) in tetrahedral site. IR spectrum confirms the presence of sulphate and hydroxyl groups in the mineral. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Fabrication and magnetic properties of Cu50(Fe69Si10B16C5)50 thin microwires

In this work, we study the granular samples of mixed Cu₅₀(Fe₆₉Si₁₀B₁₆C₅)₅₀ composition where half of alloy composition is commonly used amorphous soft magnetic material and the other half-Cu. Glass covered Cu₅₀(Fe₆₉Si₁₀B₁₆C₅)₅₀ microwires were produced and their magnetic properties were studied. The evolution of the structure after the annealing was observed using X-ray diffraction with Cu K_α radiation. The as-prepared Cu₅₀(Fe₆₉Si₁₀B₁₆C₅)₅₀ microwires present a relatively low coercivity of about 5 Oe and exhibit non-regular hysteresis loop typical behavior for two-phases systems. Annealing resulted in magnetic hardening of the samples with coercivity of about 50 Oe. The variation of the coercivity and remanent magnetization with the temperature at 5–300 K were obtained from those curves. Temperature dependence of magnetization at 5–300 K exhibits significant difference between field-cooled and zero-field cooled behaviour. Observed dependences interpreted in terms of two-phase structure of as-prepared samples and evolution of the structure under annealing.     

Crystal structure of copper(II)mellitate, [Cu3.5C6(COO)5(COOH)(OH)2(H2O)8.5]·4.5H2O

The crystal structure of copper(II)mellitate, Cu_3.5C₁₂H₂₉O₂₇, has been determined by X-ray analysis. The complex crystallizes in the orthorhombic space groupIba2, with unit-cell dimensionsa=19.274(3),b=21.054(7),c=12.956(4) Å. The structure was deduced by the direct method with the help of the Patterson method and refined by the block-diagonal least-squares technique to a finalR value of 0.037 for 2995 observed reflections. Among six carboxyl groups of mellitic acid, five groups lose protons and form coordinate bonds to four copper atoms, and the remaining group forms hydrogen bonds to the water of crystallization and coordinated water. The configuration around copper is distorted-pyramidal, with the Cu-O bond distances of 1.896(7) to 2.425(7) Å.