Cu-O Distances Research Articles

Crystal structure of [Cu2(II)(dmpa)2(p-Cl-C6H5COO)2] (Hdmpa = N,N-dimethyl-3-amino-1-propanol)

The copper complex, [Cu2(II)(dmpa)2(p-Cl-C6H5COO)2], has been prepared and its structure determined using X-ray crystallography. The dimer is a di-μ2-alkoxo complex which is a five-coordinate copper dimer with unsupported alkoxo bridges. The complex crystallizes in the triclinic space group P-1 with a = 11.384(2), b = 14.636(5), c = 9.609(2) A, α = 100.07(2), β = 104.33(3), γ = 72.79(2)°, V = 1471.8(7) A3, and Z = 2. The structure is comprised of discrete binuclear clusters in which the metal atoms are bridged by two alkoxo oxygens of the dmpa− ligands. The Cu-O and Cu-N distances are in good agreement with those found for other copper(II) aminoalcoholato complexes. The Cu···Cu distance is 2.9765(6) A. In the crystal, every two dimeric coordination molecules are combined together by the recognition through intermolecular hydrogen-bonding interactions between the apical water molecule and the non-coordinated O atom from the p-chlorobenzoato ligand, forminga tetramer.

THE POLYMERIC COPPER COMPLEX 2,2′-BIPYRIDINE-N,N′-(μ-MALEATO-O,O′:O″)COPPER(II) DIHYDRATE

Preparation and isolation of the polynuclear copper(II) complex, {[Cu(bipy)(maleato)] · 2H2O} n , was accomplished by reaction of an aqueous solution containing sodium maleate and an ethanolic solution of Cu(NO3)2·4H2O and bipy. The crystal structure of the title complex was determined by single-crystal X-ray methods. The structure consists of one-dimensional infinite chains. The copper atom is five-coordinate and presents a square-pyramidal coordination sphere, which consists of the two imine N atoms of bipy and two terminal carboxylate O atoms of a maleate2- ligand in the basal plane with Cu-N bond distances of 2.016(3) and 1.987(3) A and Cu-O distances of 1.909(2) and 1.947(2) Å, respectively. In the apical site an O atom of the maleate2- ligand from an adjacent complex coordinates to copper (2.264(2) Å). The coordination fashion of the maleato ligand is also confirmed by the IR spectrum.

A redetermination of bis(ethylenediamine-N,N')bis(perchlorato-O)copper(II)

Reaction of copper(II) perchlorate with excess ethylenediamine (en) in aqueous solution gave the title complex, [Cu(ClO 4 ) 2 (C 2 H 8 N 2 ) 2 ]. The cation is centrosymmetric with a mean Cu-N distance of 2.016 (2) A. There are semi-coordinate bonds to the perchlorate ions with a Cu-O distance of 2.579 (4) A. The N-Cu-N angle is 84.69 (9)°, as expected for chelating en. The structure is stabilized by hydrogen bonds from three of the perchlorate O atoms to amino H atoms within each molecule and between molecules, linking them into chains.

N,N'-Bis(5-bromosalicylidene)-1,3-diaminopropane]copper(II)

The title compound, [Cu(C 17 H 14 Br 2 N 2 O 2 )], has a crystallographic twofold axis. The coordination geometry about the Cu II centre is a tetrahedrally distorted square plane formed by the four-coordinate N 2 O 2 donor set of the Schiff base imine-phenol ligand. The Cu-N and Cu-O distances are 1.967 (5) and 1.914 (4) A, respectively.

{[μ-N,N'-Bis(salicylidene)-1,3-propanediaminato]-copper(II)}dichloromercury(II)

The title compound, [CuHgCl 2 (C 17 H 16 N 2 O 2 )], is a hetero-dinuclear complex containing Cu II and Hg II ions. The Cu II centre has a distorted square-planar coordination involving two O and two N atoms from the imine-phenol ligand, with Cu-O distances of 1.920 (3) and 1.926 (2) A, and Cu-N distances of 1.966 (3) and 1.986 (4) A. The coordination around the Hg II centre consists of two chloride ions at distances of 2.343 (1) and 2.325 (2) A, and two phenolic O atoms of the organic ligand at distances of 2.516 (2) and 2.421 (3) A. The Cu...Hg separation is 3.5301 (8) A.

Trans-Bis(acetato-O)bis(2-amino-6-methylpyridine-N)copper(II)

In the title compound, [Cu(C 2 H 3 O 2 ) 2 (C 6 H 8 N 2 ) 2 ], the Cu atom is surrounded by two O atoms from the two mono-dentate acetate ligands and by two pyridine N atoms from the two 2-amino-6-methylpyridine ligands in a trans square-planar arrangement. The Cu-O and Cu-N distances are 1.952(2) and 2.046 (2) A, respectively. The complex has an inversion centre. The remaining carboxylate O atoms are located at 2.764 (3) A from the Cu atom, above and below this plane. The coordination around the Cu atom can therefore be described as (4+2). The pyridine ring is twisted 73.2 (1)° with respect to the plane formed by the Cu, the N and the more strongly bonded O atoms.

{[μ-Bis(salicylidene)-1,3-propanediaminato]-(3-methylpyridine)copper(II)}diiodozinc(II)

The title complex, [CuZnI 2 (C 17 H 16 N 2 O 2 )(C 6 H 7 N)], consists of a doubly oxygen-bridged heteronuclear dimeric complex. The Cu atom has a distorted square-pyramidal environment involving two O atoms and two N atoms of the bis(salicylidene)-1,3-propanediaminate (SALPD 2- ) ligand, and an N atom of the 3-methylpyridine group. The Cu-O distances in the coordination plane are 1.973 (3) and 1.974 (2) A, and the average Cu-N distance is 2.088 (4) A. In the bridging plane, the Cu-O-Zn, O-Zn-O, Zn-O-Cu and O-Cu-O angles are 102.5(1), 76.7 (1), 102.7(1) and 77.9 (1)°, respectively. The dihedral angle between the coordination plane around the Cu atom and the 3-methylpyridine group is 88.4 (1)°. The Cu…Zn distance is 3.1013 (7) A.

{[μ-Bis(salicylidene)-1,3-propanediaminato]-copper(II)}diiodozinc(II)

The title compound, [CuZnCl 2 (C 17 H 16 N 2 O 2 )], is a double oxygen-bridged hetero-dinuclear complex. The Cu 2+ atom has a distorted square-planar environment involving the two O and two N atoms from the bis(salicylidene)-1,3-propanediaminate (SALPD 2- ) ligand. The average Cu-O distance is 1.940(3) A and the average Cu-N distance is 1.966 (3) A. The coordination around the Zn 2+ atom is distorted tetrahedral, with average Zn-O and Zn-Cl distances of 2.007(3) and 2.208 (1) A, respectively. In the bridging plane, the Zn-O1-Cu, Zn-O2-Cu, O1-Zn-O2 and O1-Cu-O2 angles are 102.4 (1), 102.3 (1), 75.0 (1) and 78.1 (1)°, respectively.

A copper(II) dimer: aqua(μ-2,2'-bipyrimidine-N,N')(perchlorato)bis{[2,6-bis(2-pyridyl)pyridine-N,N',N'']copper(II)} triperchlorate

The title compound, [Cu 2 (ClO 4 )(C 8 H 6 N 4 )(C 15 H 11 N 3 ) 2 -(H 2 O)](ClO 4 ) 3 , consists of a dinuclear copper(II) unit, the bridge being the bipyrimidine (bipym) ligand, which contains a twofold rotation axis. The Cu atoms are six-coordinated by five N atoms from the bipym and terpyridine (terpy) molecules, and by an O atom that belongs either to a water molecule or a perchlorate anion, presenting a distorted octahedral geometry. The equatorial Cu-N distances range between 1.943 (3) and 2.056 (3) A. One apical position is occupied by a bipym N atom at a distance of 2.328 (3) A, while the other apex of the octahedron is occupied alternatively by the O atom of the water molecule or an O atom of the perchlorate, with Cu-O distances of 2.445 (11) and 2.721 (11) A, respectively. Most of the remaining perchlorate O atoms are disordered.

Cis-Bis(2-amino-1,3-benzothiazole-N3)bis(formato-O,O')copper(II)

The title complex, cis-bis(2-amino-1,3-benzothiazole-N 3 )bis(formato-O,O')copper(II), [Cu(CHO 2 ) 2 (C 7 H 6 N 2 S) 2 ], displays C 2 symmetry with the Cu atom adopting a distorted octahedral (4 + 2) coordination. The four closest donor atoms are two N atoms of 2-amino-benzothiazole and two O atoms of the carboxylate groups. They form a distorted square-planar arrangement, with Cu-N and Cu-O distances of 1.991(2) and 1.993 (2) A, respectively. Two longer out-of-plane Cu-O bonds [2.538 (2) A] from the remaining O atoms of the formate groups complete the strongly distorted square-bipyramidal coordination of the Cu atom. The H atoms of each amino group of the 2-aminobenzothiazole molecules form intra- and intermolecular hydrogen bonds with O atoms from the carboxylate groups. Intermolecular S...S secondary bonding of 3.502 (2) A is observed between neighbouring chains of molecules connected by hydrogen bonds.

Aquatetrakis[(4-chlorobenzoato)(μ3-2-dimethylaminoethanolato)copper(II)] hydrate

A cubane-type core has been found in the tetrameric title complex, aqua-1κC-tetrakis(4-chlorobenzoato)-1κC,2κC,3κC,4κC-tetrakis[μ 3 -(2-dimethylaminoethanolato)-κ 3 O:O:O]-tetrahedro-tetracopper(II) hydrate, [Cu 4 (C 7 H 4 ClO 2 ) 4 (C 4 H 10 NO) 4 (H 2 O)].H 2 O. The structure of the complex molecule is composed of two ethanolate O-bridged dimers, with Cu-O bond lengths in the range 1.919 (5)-1.979 (5) A, and Cu…Cu distances of 2.855(2) and 2.890(2)A. The dimers are bridged into the tetrameric unit by triply bridging ethanolate O atoms, with Cu-O distances in the range 2.417 (5)-2.618 (5) A. Of the four Cu atoms, three are five-coordinated and one is six-coordinated.

Structure and Dynamical Behaviour of Bis(N-Diisopropoxy-Phosphorylthiobenzamido) Copper(II)

Among the new compounds of N-(thio)phosphorylthiómides. the copper(II) complex with N-diisopropoxyphosphorylthiohenzamide (Cul. 2) exhibits series of unusual properties which have been extcnsively investigated in the present work. The X-ray structure of CuL2 has been determined Crystals of CuL2 are monoclinic. P21/c, a = 15.610, b = 11.880, and c = 18.320 Å, β = 106.74°. Z = 4. The CuL2 complex has the cis-structure with Cu-S distances ranging from 2.238 to 2.253 Å and Cu-O distances being from 1.919 to 1.937 Å (Figure).

Ion-Pair Charge-Transfer Complexes Based on (o-Phenylenebis(oxamato))cuprate(II) and Cyclic Diquaternary Cations of 1,10-Phenanthroline and 2,2'-Bipyridine: Synthesis, Crystal Structure, and Physical Properties.

The ion pair charge-transfer (IPCT) complexes (C(14)H(12)N(2))[Cu(opba)].3H(2)O (1) and Na(2)(C(12)H(12)N(2))[Cu(opba)](2).4H(2)O (2), opba = o-phenylenebis(oxamate), have been isolated. Both compounds crystallize in the triclinic space group P&onemacr;. Crystal data for the compounds 1, a = 7.3216(13) Å, b = 10.1756(9) Å, c = 16.4890(16) Å, alpha = 107.786(8) degrees, beta = 94.79(1) degrees, gamma = 104.16(1) degrees, V = 1117.4(3) Å(3), Z = 2, R = 0.033 for 5332 observed reflections with I > 3sigma(I); 2, a = 6.732(3) Å, b = 11.169(3) Å, c = 12.126(2) Å, alpha = 111.01(2) degrees, beta = 102.71(3) degrees, gamma = 93.57(3) degrees, V = 820.1(5) Å(3), Z = 2, R = 0.065 for 3354 observed reflections with I > 3sigma(I). The crystal structures consist of alternated anion complex and diquaternary cation layers pi-pi interacting through the corresponding aromatic rings. The metallic layers contain the [Cu(opba)](2)(4)(-) dimeric group where the copper(II) ions are in square-pyramidal environment. For both compounds an ion-pair charge-transfer (IPCT) band is observed at 517 nm. Their thermal behavior has also been explained on the basis of the different crystal arrangements. The dimeric nature of compound 1 is clearly confirmed by the observation of temperature-dependent ESR transitions between its singlet and triplet states. The |J| value, determined from the positions of these transitions, is 0.085 cm(-)(1) at room temperature and increases notably with decreasing temperature being 0.14 cm(-)(1) at 4.2 K. Comparison of these exchange constants with those observed for other carboxylate-bridged copper compounds allow us to deduce that the temperature dependence of J is due to lattice shrinkage leading to appreciable change of the Cu-O(ap) distance. The ESR spectrum of compound 2 is characteristic of an axial g-tensor with g( parallel) = 2.178 and g( perpendicular) = 2.049, showing a weak half-field DeltaM(s) = 2 transition in agreement with the dimeric nature of the complex. The thermal evolution of the magnetic susceptibility corresponds to a compound with weak antiferromagnetic interactions. The best fit of the magnetic data to a dimer S = (1)/(2) model gives J = -0.8 cm(-)(1), in good agreement with the topology of the bridging unit with the magnetic orbitals in parallel planes and a Cu-O-Cu angle of 95.4 degrees.

Superconducting Single Crystals of Tl2Ba2CaCu2O8 and YBa2Cu4O8: Crystal Structures in the Vicinity of Tc

The structures of superconducting Tl 2 Ba 2 CaCu 2 O 8 (T c ∼ 110 K) and YBa 2 Cu 4 O 8 (T c ∼70 K) were investigated by single-crystal X-ra y diffraction techniques in a wide temperature range. Some of the structure parameters show anomalous behaviour in the vicinity of the critical temperature. The most pronounced structural change is the shift of the apical O atoms in CuO 5 pyramids towards the CuO 2 planes, indicating charge redistribution near T c . This behaviour of the apical O atoms seems to be the common structural feature of hole-doped high-T c superconductors. Another effect of charge redistribution at T 1 concerns a very small decrease of in-plane Cu-O distances and/or O-O distances in CuO 5 pyramids. Both effects represent an averaged structure response to charge (hole) redistribution upon the phase transition to the superconducting state.

μ-Acetato-μ-aqua-μ-hydroxo-bis[(1,4-dimethyl-1,4,7-triazacyclononane-κ3N)copper(II)] Diperchlorate

The structural characterization of the title complex, [Cu2(OH)(C2H302)(C 8 H 19 N 3 ))2(H 2 O)](ClO 4 )2, provides only the third example of a binuclear copper complex containing a bridging water molecule. The three bridging groups (aqua, acetato and hydroxo) are all different, a rare feature for spontaneous self-assembly reactions. The resulting geometry about the two Cu atoms is distorted octahedral, with the Cu-O(H) distance of 1.963 (2) A distinguished from the Cu-O(H 2 ) distance of 2.737 (5) A. The cation has crystallographically imposed mirror symmetry.

Bis[N-(2-bromo-4-methylphenyl)naphthaldiminato]copper(II)

The title compound, bis[1-(2-bromo-4-methylphenyliminomethyl)-2-naphtholato-N,O]copper(II), [Cu(C 18 H 13 BrNO) 2 ], has crystallographic inversion symmetry. The Cu II ion shows a pseudo-square-planar coordination. The Cu-N and Cu-O distances are 1.990(4) and 1.880 (4) A, respectively. The Cu II ion is in an approximate octahedral environment if bromine is included in the description, with a non-bonded Cu...Br distance 3.296 (1) A.

Detailed structure of a Pb-dopedBi2Sr2CuO6superconductor

The crystal structure of ${(\mathrm{B}\mathrm{i}}_{1.82}{\mathrm{Pb}}_{0.18})$ ${(\mathrm{S}\mathrm{r}}_{1.84}{\mathrm{Pb}}_{0.16})$ ${\mathrm{CuO}}_{6}$ was determined from single-crystal intensity data measured on a four-circle diffractometer. The structure is orthorhombic, space group Cccm (No. 66); the lattice parameters: $a$=5.392(3) \AA{}, $b$=24.603(5) \AA{}, $c$=5.300(3) \AA{}, $V$=703.2 (5) ${\mathrm{\AA{}}}^{3}$ (the space group can be denoted as Amaa by a cyclic transformation of the cell constants). The $R$ value was 0.048 for 418 unique reflections with $I>3.00$ $\ensuremath{\sigma}(I).$ One of the O atoms bonded to Bi ions is disordered at two sites with a half occupancy and ${B}_{\mathrm{eq}}$=3.6(6) ${\mathrm{\AA{}}}^{2};$ although the thermal parameter is not so large as that reported by Torardi et al. [Phys. Rev. B 38, 225 (1988)], the disorder suggests that the crystal has a lower symmetry. The valence state of the Cu ion in the present compound was evaluated to be trivalent based on the Cu-O distances [Asbrink and Norrby, Acta Crystallogr. B 26, 8 (1970)] and the valence of Bi was estimated in comparison with that in other compounds. The O(3) sublattice dynamics in these types of superconductors is discussed based on the structural investigations.

Electron-energy-loss spectroscopy studies of Cu-α-Al2O3interfaces grown by molecular beam epitaxy

Abstract The electron-energy-loss near-edge structure (ELNES) of a Cu-α-Al2O3 interface grown by molecular beam epitaxy has been studied using spatial difference electron-energy-loss spectroscopy in the scanning transmission electron microscope. Interpretation of the interface-specific Cu L2,3, Al L2,3 and O K ELNES components implies the existence of Cu-O bonding at the interface together with the retention of a local octahedral oxygen coordination of aluminium atoms and hence their non-participation in the interface plane. There is significant evidence for interfacial charge transfer from the copper layer to the oxygen layer, resulting in the existence of one monolayer of copper at the interface nominally in the Cu+ oxidation state. Furthermore, the ELNES studies reveal that the interfacial Cu-O bonds are of mixed ionic-covalent character. This becomes apparent when considering the O K ELNES where the presence of hybridized Cu 3d-O 2p states is indicated. The basal plane of α-Al2O3 at the interface is terminated by a layer of oxygen atoms which is directly bonded to the copper lattice. This chemical information was employed as an initial assumption in the subsequent simulation of experimental high-resolution transmission electron microscopy (HRTEM) images of the same interface. A structural model for the atomistic arrangement at the interface was derived which exhibited a projected Cu-O distance of 0.2 nm. Since the O K ELNES provides information on medium-range order, the HRTEM-derived model of the interface was then used as input for the simulation of the experimental interface-specific O K ELNES component using multiple-scattering calculations. Excellent agreement between the theoretical and experimental ELNES results confirms the HRTEM model and rules out the possibility of an aluminium-terminated α-Al2O3 basal plane at the interface. This study attempts to demonstrate the synergism between HRTEM and spatially resolved electron-energy-loss spectroscopy measurements for structure determination and highlights the self-consistent aspect of such combined information.

First principles study of adsorbed Cun (n=1–4) microclusters on MgO(100): Structural and electronic properties

We present a density functional study of the structural and electronic properties of small Cun (n=1,4) aggregates on defect-free MgO(100). The calculations employ a slab geometry with periodic boundary conditions, supercells with up to 76 atoms, and include full relaxation of the surface layer and of all adsorbed atoms. The preferred adsorption site for a single Cu adatom is on top of an oxygen atom. The adsorption energy and Cu–O distance are ES−A=0.99 eV and dS−A=2.04 Å using the Perdew–Wang gradient corrected exchange correlation functional. The saddle point for surface diffusion is at the “hollow” site, with a diffusion barrier of around 0.45 eV. For the adsorbed copper dimer, two geometries, one parallel and one perpendicular to the surface, are very close in energy. For the adsorbed Cu3, a linear configuration is preferred to the triangular geometry. As for the tetramer, the most stable adsorbed geometry for Cu4 is a rhombus. The adsorption energy per Cu atom decreases with increasing the size of the cluster, while the Cu–Cu cohesive energy increases, rapidly becoming more important than the adsorption energy.

Short-range structural properties ofNd1.85Ce0.15CuO4andNd2CuO4studied by multiple-scattering EXAFS data analysis

An accurate multiple-scattering Cu $K$-edge extended x-ray-absorption fine-structure (EXAFS) study of the average local structure of ${\mathrm{Nd}}_{1.85}{\mathrm{Ce}}_{0.15}{\mathrm{CuO}}_{4}$ and ${\mathrm{Nd}}_{2}{\mathrm{CuO}}_{4}$ is presented in the range of temperature 5--150 K. Clear differences between experimental EXAFS signals of doped and undoped compounds recorded at the same temperature are found. Shortening of 0.015 \AA{} of the average Cu-Nd/Ce distance is unambiguously detected in the doped-superconducting compound. We show that the contraction of the unit cell along the $c$ direction can be assigned to the shift of the Nd/Ce atoms toward the adjacent ${\mathrm{CuO}}_{2}$ plane. No evidence for anomalies of the in-plane Cu-Cu and Cu-O distance distribution is found as a function of temperature and doping. The strong multiple-scattering signal associated with the quasilinear Cu-O-Cu chains in the ${\mathrm{CuO}}_{2}$ planes is used to evaluate the angle distribution at the oxygen site, using a suitable model describing a realistic three-atom vibrating system. Differences between the doped and the undoped compound are detected showing that the angle distribution is broader below ${T}_{c}$ in the doped compound. The increased width of the angle distribution is consistent with the existence of local modes or permanent structural distortions involving the in-plane oxygens.