Arrangement Of Cu Research Articles

Anion-templating self-assembly of [Cu 2(OMe) 2] 2+ SBUs depending on the size of the anion in the solid state

The solution reaction of btp [2,6-bis( N1-1,2,4-triazolyl)pyridine] with copper acetate afforded a secondary building unit (SBU) precursor of [Cu 2(OAc) 4(btp) 2] · 2MeOH ( 1) which yielded the [Cu 2(OMe) 2] 2+ SBU by the reaction of 1 with CuX 2 salts (X = [BF 4] −, [ClO 4] − and [OTf] −) in methanol and acetonitrile mixture. According to solid-state structural analysis, self-assembly of SBUs is dependent on the size of the anion. In the case of [BF 4] − and [ClO 4] −, SBUs are self-assembled to be 3D cages of [[[Cu 4(μ-OMe) 4(μ-btp) 4(BF 4) 2(MeCN) 2] ⊃ (BF 4)](BF 4)][[[Cu 4(μ-OMe) 4(μ-btp) 4(BF 4)(MeOH)(MeCN) 2] ⊃ (BF 4)](BF 4) 2] ( 2) and [[Cu 4(μ-OMe) 4(μ-btp) 4(ClO 4) 2(MeCN) 2] ⊃ (ClO 4)](ClO 4) · 2H 2O ( 3) by the anion-templating effect, where two SBUs are bridged by four btp ligands. The bending of Cu 2O planes along the O⋯O hinge causes the btp ligands to get close enough to interconnect two [Cu 2(OMe) 2] 2+ SBUs in addition to the orthogonal arrangement of Cu⋯Cu axes of each SBU. Meanwhile, the large anion [OTf] − was not capable of the 3D cage but a 1D infinite coordination polymer of [[Cu 2(μ-OMe) 2(μ-OTf) 2(btp) 2](H 2O)] n ( 4) in which SBUs are doubly bridged by btp ligands in a zigzag pattern.

Phase imaging using time-of-flight neutron diffraction

A technique that allows the spatial distribution of crystallographic phases in the interior of an object to be reconstructed from neutron time-of-flight (TOF) diffraction is described. To this end, the shift of the Bragg peaks due to the so-called `geometrical aberration' is exploited. A collimated incident white beam is used to perform a translational or rotational scan of the object whilst collecting a TOF data set for each sample position or orientation. Depending on the location of any scattering material along the line of the incident beam path through the object, the measuredd-spacings of the corresponding Bragg peaks are shifted with respect to their nominal values, which are attained only at the geometrical centre of the instrument. Using a formula that is usually employed to correct for sample offset, the phase distribution along the incident beamline can be directly reconstructed, without the need to perform a tomographic reconstruction. Results are shown from a demonstration experiment carried out on a cylindrical Al container enclosing an arrangement of Cu and Fe rods. On the basis of this formalism, an optimized experimental geometry is described and the potential and limits of this technique are explored, as are its applicability to X-ray and constant-wavelength neutron diffraction.

Ferromagnetic Cu 8 pinwheel clusters as building blocks for larger magnetic networks: Long-range structural and magnetic ordering

The structural and magnetic properties of a series of Cu 8 pinwheel clusters with the tritopic ligands 2POMP, 2POPP, Cl2POMP and SEt2POMP are described. Two different ligand binding modes lead to two different arrangements of Cu–Cu bridge connections within the pinwheel. In one case, all the Cu(II) centers are bridged by hydrazone oxygen atoms, and the Cu–Cu distances are all similar (∼4 Å). In the other case, the central Cu(II) centers are bridged by hydrazone oxygen atoms, while the peripheral Cu 2+ cations are bridged to the core by diazine (N–N) groups. In both cases, the bridges are orbitally strictly orthogonal and so ferromagnetic exchange dominates. In the complex [(2POMP-2H) 4Cu 8Br 6](CuBr 4)(H 2O) 11 ( 1) bromide ions bridge the peripheral Cu(II) centers of adjacent Cu 8 pinwheel cluster molecules forming a 2D network with additional CuBr 4 2 - ions occupying cavities in the lattice. In [(Cl2POMP-2H) 4Cu 8(N(CN) 2) 8](H 2O) 9(CH 3CN) ( 3), nitrogen atoms of the coordinated dicyanamide (dca) ions bound to the peripheral Cu(II) centers interact with ligand bound chlorine atoms of adjacent molecules to form stacks of pinwheels. In [(Set2POMP-2H) 4Cu 8(H 2O) 8](PF 6) 8(CH 3OH) 6(CH 3CN) 1.5 ( 4) relatively short S⋯S contacts exist between pinwheels and cause stacking in the extended structure. Surprisingly, there is evidence for long-range magnetic interactions in 3 via the intermolecular contacts, but not in 1, which has direct bonding between pinwheel subunits. Exchange integrals within the pinwheel clusters fall in the range J = 4–7 cm −1.

Two helical one-dimensional copper(II) coordination polymers based on N-(2-hydroxylbenzyl)glycine and N-(2-hydroxylbenzyl)- l-alanine: Syntheses, crystal structures and magnetic studies

Two new helical Cu(II) coordination polymers, [Cu(2,2′-bpy)(Hsgly)]Cl · 2H 2O(H 2sgly = N-(2-hydroxylbenzyl)glycine) ( 1) and [Cu(2,2′-bpy)(Hsala)](NO 3) · 2H 2O(H 2sala = N-(2-hydroxylbenzyl)- l-alanine) ( 2) were synthesized. Single crystal X-ray diffraction analysis indicated that both complexes showed helical chains arrangement of Cu(II) centers bridged by carboxyl groups. The magnetic measurements showed complex 1 exhibited ferromagnetic interaction while there was no interaction between the Cu(II) centers in complex 2.

High-resolution transmission electron microscopy study of ordered or disordered arrangements of Cu, C and N in the charge-reservoir blocks of a series of high-Tc superconductors: (Cu, C, N)Sr2Can-1CunOy (n = 1-6)

Abstract A series of new oxycarbonitrate superconductors, (Cu, C, N)Sr2Can-1CunOy, (n = 1–6), recently prepared in a Sr-Ca-Cu-C-N-O system under a high pressure of 5–6 GPa, are examined by electron diffraction and high-resolution transmission electron microscopy, to reveal arrangements of Cu and C (N) in the charge -reservoir blocks (CRBs). Ordered arrangements of Cu and C (N) are observed in the compounds with n = 1–4, and almost random arrangements for those with n = 5–6. In the first two series of compounds, (Cu, C, N)-1201 (n = 1) and (Cu, C, N)-1212 (n = 2), an ordering scheme of -Cu-C(N)-C(N)-C(N)-Cu-with fourfold periodicity is observed, indicating that the ratio of Cu to C (N) in the CRB is 1 to 3. For (Cu, C, N)-1234 (n = 4), with highest T c of 113 K in the series, the ordering scheme of Cu-C(N)-Cu-C(N)-Cu- with twofold periodicity is observed, indicating that the ratio of Cu to C (N) in the CRB is 1 to 1. Both types of ordering structure coexist in the n = 3 compound, (Cu, C, N)-1223. In the last two members, (Cu, C, N)-1245 (n = 5) and (Cu, C, N)-1256 (n = 6), no evidence of ordering was observed, suggesting that Cu, C and N are distributed almost randomly in the CRBs. Such relations between the ordering scheme and n parameters are also observed locally in the crystals which contain many intergrowth defects.

HRTEM study of new series of oxycarbonitrate superconductors (Cu,C,N)Sr2Ca(n - 1)Cu(n)O(y) (n = 1-6).

Arrangements of Cu and anion groups (CO3 and NO3) in the charge-reservoir (CR) blocks of a series of new oxycarbonitrate superconductors (Cu,C,N)Sr2Ca(n - 1)Cu(n)O(y) (n = 1-6) were examined by means of electron diffraction and high-resolution transmission electron microscopy (HRTEM). The first three members with n = 1-3 [Tc = 33 K (n = 1), 91 K (n = 2), 90 K (n = 3)] show the 4a0-type superstructures with periodic arrangements, [-Cu-X-X-X-Cu-X-X-X-Cu-] (X = CO3, NO3), in the CR blocks. The third member (n = 3) partly contains the 2a0-type of superstructure with [-Cu-X-Cu-X-Cu] in the CR blocks. The fourth member with n = 4 (Tc = 113 K) contains only the 2a0-type of superstructure. The higher members, with n = 5 (Tc = 65 K) and n = 6 (Tc = 52 K), show no evidence of ordering in the CR blocks, suggesting random arrangements of Cu and anion groups.

High-resolution transmission electron microscopy study of ordered or disordered arrangements of Cu, C and N in the charge-reservoir blocks of a series of high-Tc superconductors: (Cu, C, N)Sr2Can-1CunOy (n = 1–6)

A series of new oxycarbonitrate superconductors, (Cu, C, N)Sr2Can-1CunOy, (n = 1–6), recently prepared in a Sr-Ca-Cu-C-N-O system under a high pressure of 5–6 GPa, are examined by electron diffract...

Color and Conductivity in Cu2O and CuAlO2: A Theoretical Analysis of d10···d10 Interactions in Solid-State Compounds

The influence of homoatomic d10···d10 interactions in the structural and physical properties of some copper-containing oxides has been investigated by using semiempirical band structure calculations of the extended Huckel type. Comparison of the band structures of CuAlO2 and Cu2O, two compounds with Cu(I) ions in practically identical coordination environments, reveals that the spatial arrangement of Cu···Cu contacts is responsible for their markedly different electrical and optical properties. The three-dimensional net of short Cu···Cu distances present in Cu2O is found to be essential for the appearance of color in this p-type semiconductor. In doped CuAlO2, on the contrary, the 2-D nature of the array of Cu···Cu contacts leads to optical transparency and a lower conductivity if compared to cuprite.

Trinuclear copper(II) complexes with bridging (N–N) diazine ligands: structural and magnetic studies

The polytopic ligands 2poap and po2p have a linear disposition of coordination pockets suitably disposed to bind metal ions in close proximity and produce linear trinuclear copper(II) complexes. The complexes [Cu3(2poap − 2H)(CH3CO2)4]·3H2O (1), [Cu3(2poap − 2H)(H2O)(DMF)3(CH3OH)2](BF4)4 (2), and [Cu3(po2p − H)2(H2O)2](ClO4)4·2H2O (3) have a linear arrangement of Cu(II) centres linked by a trans arrangement of N–N single bonds. Each metal is assigned a dx2 − y2 magnetic ground state, and the trans diazine bridging arrangement leads to strong antiferromagnetic coupling in complete agreement with previous magnetostructural correlations relating the twist of the copper magnetic planes around the N–N bond to the exchange integral.

High-pressure synthesis and properties of a new oxycarbonitratesuperconductors in the Sr-Ca-Cu-N-C-O system

Recently, oxycarbonitrate superconductors (Cu, N, C)Sr2Can-1CunOy were prepared under high pressure.They have M-12(n-1)n type structures with the M sites occupied by mixedatoms of (Cu, N, C). The phases with n = 3-6 have been isolated, identifiedand characterized. However, the n = 1 and 2 members have not been reported andit is even unknown whether they exist or not. In the present study, weperformed systematic high-pressure synthesis experiments for theSr-Ca-Cu-N-C-O system to find the n = 1 and 2 members. The n = 1 phasehas a somewhat different characteristic, i.e. its M site is occupied only byC and N without partial replacement of Cu, having a composition of (N, C)Sr2CuOy. On the other hand, in the n = 2 phase the M site isoccupied by the three atoms Cu, N and C, as in the n = 3-6 members. These twonew phases show superconductivity below 33 and 91 K, respectively. Thesuperstructure due to an ordered arrangement of Cu, C and N was studied usinga high-resolution electron microscope. A superstructure with 4a×b×2c representing a simple tetragonal cell with a, b, c wasobserved in the n = 2 phase.

Crystal structure and twinning of monoclinic Cu 2SnS 3

Crystals of monoclinic Cu 2SnS 3 have been prepared by a conventional solid-state reaction. The crystal structure has been refined from a twinned specimen using X-ray diffraction data collected with an automatic diffractometer applying a high-dimensional twin refinement technique: space group Cc, a = 6.653(1), b = 11.537(2), c = 6.665(1) Å, β = 109.39(3)°, Z = 4, R F = 0.036, and wR F = 0.038 for 1237 reflections and 52 structural parameters. The structure is a superstructure of the sphalerite type structure, based on cubic close packing of S with order arrangement of Cu and Sn in tetrahedral sites, and it is isomorphic with Cu 2GeS 3 and Cu 2SiS 3.

High-pressure synthesis and Jc-related properties of Cr- and V-based high Tc superconductors

Homologous series of cuprate superconductors (Cu,Cr)Sr 2Ca n−1 Cu n O 2 n+3 [(Cu,Cr)-12( n−1) n, n=1–9] and (Cu,V)Sr 2Ca n−1 Cu n O 2 n+3 [(Cu,V)-12( n−1) n, n=3–7] prepared under high pressure were discussed. They have M-12( n−1) n-type structures with the M site occupied by the (Cu,Cr) [or (Cu,V)] mixed atom. The highest T c in each series is 103 K for (Cu,Cr)-1223 and 107 K for (Cu,V)-1234. The n=3 phases of both series show extremely high critical current densities and irreversibility fields which are comparable to or better than those of the YBa 2Cu 3O 7. This seems to be related to the partial occupation of the Cu atom in the charge reservoir layer and the random arrangement of Cu and Cr (or V) there.

Crystal structure and spectroscopy of a hydrogen-bridged one-dimensional Cu(II) complex containing both octahedral and square pyramidal geometries in the same unit cell

Single crystals of the helical hydrogen-bridged one-dimensional Cu(II) complex, [Cu(stpy)2(CH3COO)2(H2O)2] (1) [Cu(stpy)2(CH3COO)2(H2O)] (2), are prepared and characterized by elemental and thermal analyses, IR, electronic and X-ray crystal structure determination. The crystals are monoclinic, of space group C2/c, with unit cell parameters a = 31.842(7) A, b = 5.9829(10) A, c = 30.970(14) A, β = 111.78(3)°, Z = 4. The asymmetric unit contains two different types of Cu(II) polyhedra, namely, octahedron and square pyramid within the same unit cell. 1 has elongated octahedral geometry with two nitrogen atoms from stpy and two oxygen atoms from synmonodentate acetate ligands, transcoordinated to Cu(II) in the basal plane. The oxygen atoms of the two water molecules occupy the axial positions. 2 has Cu(II) coordination polyhedra similar to 1, except that only one of the apical positions is occupied by a water molecule. The structure consists of two independent linear chains, one involving octahedral (1) and the other involving square-pyramidal (2) polyhedra, held by hydrogen bridges. The Cu–Cu intra- and interchain separations in both 1 and 2 are 5.983 and 8.214 A. The unit cell packing shows weak π-stacking between adjacent coordinated stpy ligands in the chain, resulting in ladder-type structure. Further, the extended packing reveals helical arrangement of Cu(II) polyhedra in the lattice.

The coloring problem in Ba2Cu3VS6 †

The relative stabilities of the different arrangements of Cu(I) and V(V) cations in Ba2Cu3VS6 estimated through plane wave density functional calculations show a preference for structures which maximize the number of Cu⋯V contacts that involve d10⋯d0 interactions.

Critical current densities of high- Tc superconductors (Cu,Cr)Sr 2Ca n−1 Cu nO 2 n+3 ( n=2,3) prepared under high pressure

Critical current densities ( J c) and irreversibility fields ( B irr) of high- T c superconductors (Cu,Cr)Sr 2Ca n−1 Cu n O 2 n+3 ( n=2,3) prepared under high pressure were determined from the hysteresis in DC magnetization loop. They show higher J c values than other high- T c superconductors such as YBa 2Cu 3O 7, Bi-phases, Hg-phases, (Cu,C)-based phases, etc. for the almost entire range of temperature below T c. Their B irr values are also very high; at 77 K, for instance, B irr of (Cu,Cr)-1223 was over 5 T. In addition to the polycrystalline bulk samples, magnetically grain aligned samples of the (Cu,Cr)-phases were investigated to discuss superconductivity anisotropy. The good J c-related properties of the (Cu,Cr)-phases seem to be caused by their less anisotropic electronic structures and sufficient number of effective pinning centers due to the random arrangement of Cu and Cr in the blocking layer.

Charge density distribution in alkaline-earth cuprates with one- or two-dimensional arrangements of Cu [sbnd

We report the charge density distribution ϱ(r) ( = |φ(r)| 2 ; φ(r)wave function) of Ca 2CuO 3 with the one-dimensional Cu O chain and (Sr 0.15, Ca 0.85)CuO 2 with the two-dimensional CuO 2 plane, in comparison with that of superconducting YBa 2Cu 3O 6.9 with both the Cu O atomic arrangements. ϱ(r) was obtained by the Maximum-Entropy Method (MEM) analysis using laboratory X-ray powder diffraction data. The ϱ(r) in (Ca,Sr)CuO 2 is almost spherical, indicating that ionic features are dominant in the CuO 2 planes. This contrasts with the case of superconducting YBa 2Cu 3O 6.9, which shows remarkable overlapping between Cu 3d and O 2p orbitals. On the contrary, the ϱ(r) in Ca 2CuO 3 indicates substantial overlapping between Cu and O only along the single chain direction and no interaction between each Cu O chain.

A Triangular Copper(I) Complex Displaying Allosteric Cooperativity in Its Electrochemical Behavior and a Mixed-Valence Cu(I)-Cu(I)-Cu(II) State with Unusual Temperature-Dependent Behavior.

Reaction of the tris-chelating hexadentate podand ligand tris[3-(2-pyridyl)pyrazol-1-yl]hydroborate (Tp(Py)) with [Cu(MeCN)(4)][PF(6)] affords [Cu(I)(3)(Tp(Py))(2)][PF(6)] (1), which was crystallographically characterized. 1.(MeCN)(2): C(52)H(44)B(2)Cu(3)F(6)N(20)P, orthorhombic, Pna2(1); a = 24.592(7), b = 16.392(5), c = 13.365(5) Å; Z = 4. Each Cu(I) ion is four coordinated by one N,N '-bidentate arm from each ligand; each ligand therefore donates each bidentate arm to a different Cu(I) ion. The isosceles triangular arrangement of Cu(I) ions with N-donor ligands is reminiscent of the tricopper(I) site of ascorbate oxidase. One-electron oxidation of 1 affords the Cu(I)(2)Cu(II) complex [Cu(3)(Tp(Py))(2)][PF(6)](2) (2). The potentials of the Cu(I)/Cu(II) redox couples are affected by the ease with which the accompanying geometric rearrangement can occur. Thus, the first oxidation of 1 is facile (-0.52 V vs the ferrocene/ferrocenium couple, Fc/Fc(+)), but as a result of the concomitant structural rearrangement the second oxidation is rendered much more difficult (+0.12 V vsFc/Fc(+)) and results in slow decomposition of the product. A third oxidation does not occur at accessible potentials. This complex therefore exhibits negative cooperative behavior, in which the geometric change accompanying one metal-based redox change hinders further redox changes at other sites via an allosteric effect. EPR studies on the mixed-valence complex 2 show that in frozen glasses below 120 K the unpaired electron is delocalized over two metal centers (7-line spectrum), but above 160 K the electron becomes localized and gives a simple axial spectrum. The electronic spectrum of 2 in solution shows an intense band at 910 nm (epsilon 2100 dm(3) mol(-)(1) cm(-)(1)) which we believe to be an IVCT band. The combination of EPR and electronic spectral studies show that 2 is class III (fully delocalized over 2 centers) below 120 K but class II (localized but strongly interacting) at higher temperatures.

New series of oxysulphate superconductors (Cu 0.5S 0.5)Sr 2Ca n−1 Cu nO y ( n = 37), prepared at high pressure

A new series of oxysulphate superconductors, (Cu 0.5Sr 0.5)Sr 2Ca n−y O y was prepared at high pressure of 6 GPa and 1250°C. Five members with n = 37 were obtained in bulk. They show superconductivity with T c ranging from ≈ 60 K for n = 7 to 100 K for n = 3. HRTEM and electron diffraction observation for each member indicated an ordered arrangement of Cu and S in a (Cu,S) plane resulting in a superstructure with a s = 2 a, b s = b, c s = 2 c or a s = 2 s, b s = b, c s = c with respect to a basic tetragonal lattice, a, b, c. Local intergrowths of phases with various n values up to 13 were also observed.

X-ray emission spectroscopy with EPMA applied to high Tc Superconductors using new spectrometer crystals

The High Temperature Superconductors are characterized by a very anisotropical structure and by typical arrangements of Cu- and O-atoms within CuO2-planes. In studying the electronic structure of these compounds there is a strong demand for high resolution valence band spectroscopy. Using an electron probe microanalyzer we study the X-ray emission of O-Kga and Cu-Lα emerging from polycrystalline YBa2Cu3O7 and Tl2Ba2Ca2Cu3O10. The O-Kα emission band is analyzed using a chlinochlore crystal in (001) orientation (2d = 28.4 A). For the Cu-Lα emission band we use a beryl crystal in (10¯10) orientation (2d = 15.9 A). Furthermore, orientation dependent X-ray emission spectroscopy of single-crystalline YBa2Cu3O7 and Tl2Ba2Ca1Cu2O8 specimens was performed. We present the partial O-Kα spectra which represent the O-2pη (η = x, y, z) electronic densities of states of the valence band and compare them with calculated data.

Embedded atom method computations of structural and dynamical properties of Cu and Ag clusters adsorbed on Pd(110) and Pd(100): evolution of the most stable geometries versus cluster size

The structural stability of one- and two-dimensional arrangements of Cu and Ag clusters adsorbed on Pd(110) and Pd(100) is investigated as a function of cluster size by using embedded atom method potentials. In Cu Pd(110) , we find a remarkable stability of one-dimensional chains over two-dimensional compact arrangements, which increases with cluster size N while the opposite trend (decreasing stability with increasing size) is found in the case of Ag Pd(110) . On Pd(100) two-dimensional structures are the most stable. The diffusion mechanisms for the adatom movement on Pd(110) are elucidated via static computations and described in detail for migration along the [001] direction.