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Cu Atoms (cu + atom)

Distribution by Scientific Domains
Chemistry91%
Physics and Astronomy8%
Distribution within Chemistry
Crystallography79%
General & Introductory Chemistry13%
3 Other Subdomains8%

Selected Abstracts

Li12Cu16+xAl26,x (x = 3.2): a new intermetallic structure type

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2008
Volodymyr Pavlyuk
The new ternary lithium copper aluminide, Li12Cu16+xAl26,x (x = 3.2), dodecalithium nonadecacopper tricosaaluminide, crystallizes in a new structure type with space group P4/mbm. Among nine independent atomic positions, two Al (one of which is statistically disordered with Cu) and three Li atoms have point symmetry m.2m, two statistically disordered Al/Cu atoms are in m.. sites, one Al atom is in a 4/m.. site and one Cu atom occupies a general site. The framework of Li12Cu16+xAl26,x consists of pseudo-Frank,Kasper polyhedra enclosing channels of hexagonal prisms occupied by Li atoms. The crystallochemical peculiarity of this new structure type is discussed in relation to the derivatives from Laves phases (LiCuAl2 and Li8Cu12+xAl6,x) and to the well known CaCu5 structure. [source]

ChemInform Abstract: [Cu@Sn9]3- and [Cu@Pb9]3- : Intermetalloid Clusters with Endohedral Cu Atoms in Spherical Environments.

CHEMINFORM, Issue 33 2008
Sandra Scharfe
Abstract 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 of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

DFT calculations of light-induced excited states and comparison with time-resolved crystallographic results

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 5 2005
Philip Coppens
Abstract DFT calculations of the ground and first excited states of several transition metal complexes have been performed to complement time-resolved diffraction experiments. The results from different functionals and relativistic treatments are tested against both diffraction and spectroscopic values. Calculations of the d8,d8 complex [Pt2(pyrophosphite)4]4, quantitatively reproduce metal,metal shortening on excitation to the triplet state and support bond formation between the two metal centers, as do calculations on [Rh2(1,3-diisocyanopropane)4]2+. Results on homoleptic and heteroleptic copper(I) 2,9-dimethyl,1,10-phenanthroline (dmp) complexes, which are investigated because of their potential for solar energy capture, confirm considerable molecular deformations on excitation. The distortion calculated for the isolated complex [Cu(dmp)(dmpe)]+ (dmpe=1,2-bis(dimethylphosphino)ethane) is significantly larger than observed in the crystal, indicating the constraining effect of the crystalline environment. The change in the net charge of the Cu atom upon photo-induced metal-to-ligand charge transfer is less than 0.2 e, showing the limitations of the formal Cu(I),Cu(II) designation. Electron density difference maps show a pronounced change in electronic structure of the Cu atom on excitation. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source]

Uniaxial stress study of the Cu,H complex in ZnO

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2006
E. V. Lavrov
The cover picture of the current issue refers to the article by Lavrov and Weber which was selected as Editor's Choice [1]. The picture shows a microscopic model of the Cu,H complex investigated in the paper. The complex consists of a substitutional Cu atom at the Zn site with an H atom located between nearby O and Cu in the basal plane of the ZnO lattice. The atoms are shown in different colors: yellow for copper, red for hydrogen, cyan for oxygen, and grey for zinc. Hydrogen forms a strong bond with the O atom which gives rise to a local vibrational mode at 3192 cm,1 investigated in the paper under uniaxial stress. The c -axis is parallel to the Cu,O bond pointing to the top of the figure. The authors work at the Institute of Applied Physics/Semiconductor Physics, TU Dresden, Germany. [source]

X-ray constrained unrestricted Hartree,Fock and Douglas,Kroll,Hess wavefunctions

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 1 2010
Martin Hudák
The extension of the X-ray constrained (XC) wavefunction approach to open-shell systems using the unrestricted Hartree,Fock formalism is reported. The XC method is also extended to include relativistic effects using the scalar second-order Douglas,Kroll,Hess approach. The relativistic effects on the charge and spin density on two model compounds containing the copper and iron atom are reported. The size of the relativistic effects is investigated in real and reciprocal space; in addition, picture-change effects are investigated and discussed for the isolated Cu atom. It is found that the relativistic terms lead to changes in the densities that are much smaller than those from the X-ray constraint. Nevertheless, the use of the relativistic corrections in the ab initio model always leads to an improvement in the agreement statistics. An interesting result of the unrestricted XC technique is the possibility of obtaining experimentally derived spin densities from X-ray data. [source]

X-ray fluorescence holography: a novel treatment for crystal structure determination

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 2 2003
F. N. Chukhovskii
It is shown that it is possible to use a linear regression algorithm direct method to solve crystal structures from X-ray fluorescence holography (XFH) data. It is found that, in contrast to conventional X-ray structure determination methods, which do not always work unambiguously, the sustainable method utilizing the XFH data generally provides the unique phase-retrieval structure solution and is able, in many cases, to replace the above for determining both the absolute values (moduli) and phases of structure factors. The XFH scan with a fluorescing Cu atom from a spherical cluster of a Cu3Au single crystal, at an energy of 10,keV for the incident unpolarized plane-wave X-radiation, is numerically simulated to test the performance of the method in finding a unique solution for the structure factors involved in the restoration procedure using the linear regression algorithm. [source]

Poly[[diaqua-,-4,4,-bipyridine-dinitratodi-,- l -tyrosinato-dicopper(II)]: a chiral two-dimensional coordination polymer

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2009
Shuo Zhang
The title compound, [Cu2(C9H10NO3)2(NO3)2(C10H8N2)(H2O)2]n, contains CuII atoms and l -tyrosinate (l -tyr) and 4,4,-bipyridine (4,4,-bipy) ligands in a 2:2:1 ratio. Each Cu atom is coordinated by one amino N atom and two carboxylate O atoms from two l -tyr ligands, one N atom from a 4,4,-bipy ligand, a monodentate nitrate ion and a water molecule in an elongated octahedral geometry. Adjacent Cu atoms are bridged by the bidentate carboxylate groups into a chain. These chains are further linked by the bridging 4,4,-bipy ligands, forming an undulated chiral two-dimensional sheet. O,H...O and N,H...O hydrogen bonds connect the sheets in the [100] direction. This study offers useful information for the engineering of chiral coordination polymers with amino acids and 4,4,-bipy ligands by considering the ratios of the metal ion and organic components. [source]

The new three-dimensional supramolecule bis{,-2-[(4-hydroxybenzoyl)hydrazonomethyl]phenolato}bis[aquacopper(II)] dinitrate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2008
Hua Yin
In the title centrosymmetric binuclear complex, [Cu2(C14H11N2O3)2(H2O)2](NO3)2, the two metal centres are bridged by the phenolate O atoms of the ligand, forming a Cu2O2 quadrangle. Each Cu atom has a distorted square-pyramidal geometry, with the basal donor atoms coming from the O,N,O,-tridentate ligand and a symmetry-related phenolate O atom. The more weakly bound apical donor O atom is supplied by a coordinated water molecule. When a further weak Cu...O interaction with the 4-hydroxy O atom of a neighbouring cation is considered, the extended coordination sphere of the Cu atom can be described as distorted octahedral. This interaction leads to two-dimensional layers, which extend parallel to the (100) direction. The two-dimensional polymeric structure contrasts with other reported structures involving salicylaldehyde benzoylhydrazone ligands, which are usually discrete mono- or dinuclear Cu complexes. The nitrate anions are involved in a three-dimensional hydrogen-bonding network, featuring intermolecular N,H...O and O,H...O hydrogen bonds. [source]

Li12Cu16+xAl26,x (x = 3.2): a new intermetallic structure type

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2008
Volodymyr Pavlyuk
The new ternary lithium copper aluminide, Li12Cu16+xAl26,x (x = 3.2), dodecalithium nonadecacopper tricosaaluminide, crystallizes in a new structure type with space group P4/mbm. Among nine independent atomic positions, two Al (one of which is statistically disordered with Cu) and three Li atoms have point symmetry m.2m, two statistically disordered Al/Cu atoms are in m.. sites, one Al atom is in a 4/m.. site and one Cu atom occupies a general site. The framework of Li12Cu16+xAl26,x consists of pseudo-Frank,Kasper polyhedra enclosing channels of hexagonal prisms occupied by Li atoms. The crystallochemical peculiarity of this new structure type is discussed in relation to the derivatives from Laves phases (LiCuAl2 and Li8Cu12+xAl6,x) and to the well known CaCu5 structure. [source]

The dinuclear copper(II) complexes di-,-chlorido-bis{[N,N,-bis(4-chlorobenzyl)propane-1,2-diamine]chloridocopper(II)} and di-,-chlorido-bis{[N,N,-bis(3,4-methylenedioxybenzyl)propane-1,2-diamine]chloridocopper(II)}

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2007
Shu-Ping Yang
The two title dinuclear copper(II) complexes, [Cu2Cl4(C17H20Cl2N2)2], (I), and [Cu2Cl4(C19H22N2O4)2], (II), have similar coordination environments. In each complex, the asymmetric unit consists of one half-molecule and the two copper centres are bridged by a pair of Cl atoms, resulting in complexes with centrosymmetric structures containing Cu(,-Cl)2Cu parallelogram cores; the Cu...Cu separations and Cu,Cl,Cu angles are 3.4285,(8),Å and 83.36,(3)°, respectively, for (I), and 3.565,(2),Å and 84.39,(7)° for (II). Each Cu atom is five-coordinated and the coordination geometry around the Cu atom is best described as a distorted square-pyramid with a , value of 0.155,(3) for (I) and 0.092,(7) for (II). The apical Cu,Cl bond length is 2.852,(1),Å for (I) and 2.971,(2),Å for (II). The basal Cu,Cl and Cu,N average bonds lengths are 2.2673,(9) and 2.030,(2),Å, respectively, for (I), and 2.280,(2) and 2.038,(6),Å for (II). The molecules of (I) are linked by one C,H...Cl hydrogen bond into a complex [10] sheet. The molecules of (II) are linked by one C,H...Cl and one N,H...O hydrogen bond into a complex [100] sheet. [source]

Two-dimensional square-grid frameworks formed by self-associating copper(II) complexes with 1-(3-pyridyl)- and 1-(4-pyridyl)-substituted butane-1,3-diones

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2006
Volodimir D. Vreshch
In bis­[1-(3-pyridyl)butane-1,3-dionato]copper(II) (the Cu atom occupies a centre of inversion), [Cu(C9H8NO2)2], (I), and bis­[1-(4-pyridyl)butane-1,3-dionato]copper(II) methanol solvate, [Cu(C9H8NO2)2]·CH3OH, (II), the O,O,-chelating diketonate ligands support square-planar coordination of the metal ions [Cu,O = 1.948,(1),1.965,(1),Å]. Weaker Cu,N inter­actions [2.405,(2),2.499,(2),Å], at both axial sides, occur between symmetry-related bis­(1-pyridylbutane-1,3-dion­ato)copper(II) mol­ecules. This causes their self-organization into two-dimensional square-grid frameworks, with uniform [6.48,Å for (I)] or alternating [4.72 and 6.66,Å for (II)] inter­layer separations. Guest methanol mol­ecules in (II) reside between the distal layers and form weak hydrogen bonds to coordinated O atoms [O,O = 3.018,(4),Å]. [source]

(4-Bromo-2-formyl­phenolato)­perchlorato­(1,10-phenanthroline)­copper(II)

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2006
Hong-Yan Wu
In the title copper(II) compound, [Cu(C7H4BrO2)(ClO4)(C12H8N2)], the Cu atom is five-coordinated in a distorted square-pyramidal geometry by the N- and O-donors of 4-bromo-2-formyl­phenolate, 1,10-phenanthroline and perchlorate. Pairs of complexes are linked together by Cu,O(phenolate) and ,,, stacking inter­actions between 4-bromo-2-formyl­phenolate and 1,10-phenanthroline. Along the crystallographic a axis, the dimers are linked by hydrogen bonds between a perchlorate O atom and a 4-bromo-2-formyl­phenolate H atom, and by further ,,, stacking inter­actions. Hydrogen bonding between the Br atom and a 1,10-phenanthroline H atom takes place between the stacks of dimers. [source]

Bis­(acetone-,O)­bis(N,N,-di­methyl­ethyl­enedi­amine-,2N,N,)copper(II) diperchlorate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2004
Takashiro Akitsu
The title compound, [Cu(C4H12N2)2(C3H6O)2](ClO4)2, is the first structurally characterized CuII complex having acetone as axial ligands. The complex adopts an elongated octahedral trans -[CuN4O2] coordination geometry, with the Cu atom having 222 site symmetry. The axial Cu,O(acetone) and in-plane Cu,N bond lengths are 2.507,(5) and 2.041,(3),Å, respectively. [source]

catena -Poly­[[bis­[,-1,2-bis(1-methyl­tetrazol-5-yl)­ethane-,2N4:N4,]bis[chloro­copper(II)]]-di-,-chloro]

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2003
Dmitry O. Ivashkevich
In the title compound, [Cu2Cl4(C6H10N8)2]n, the ligand has C2 symmetry, and the Cu and Cl atoms lie on a mirror plane. The coordination polyhedron of the Cu atom is a distorted square pyramid, with the basal positions occupied by two N atoms from two different ligands [Cu,N,=,2.0407,(18),Å] and by the two Cl atoms [Cu,Cl,=,2.2705,(8) and 2.2499,(9),Å], and the apical position occupied by a Cl atom [Cu,Cl,=,2.8154,(9),Å] that belongs to the basal plane of a neighbouring Cu atom. The [CuCl2(C6H10N8)]2 units form infinite chains extending along the a axis via the Cl atoms. Intermolecular C,H,Cl contacts [C,Cl,=,3.484,(2),Å] are also present in the chains. The chains are linked together by intermolecular C,H,N interactions [C,N,=,3.314,(3),Å]. [source]

A lariat-functionalized copper(II) di­imine,dioxime complex

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2002
Salma Kiani
The dimeric title copper(II) complex, diaqua-1,O,2,O -bis[3,9-dimethyl-6-(2-pyridyl­methyl)-4,8-di­aza­undeca-3,8-di­ene-2,10-dione dioximato(1,)]-1k4N2,N4,N8,N10;1:2,5O2:N2,N4,N8,N10 -dicopper(II) diperchlorate, [Cu2(C17H24N5O2)2](ClO4)2, crys­tallizes with one Cu atom in a square-pyramidal environment and the other Cu atom displaying a distorted octahedral coordination. In each case, the four N atoms in the core of the ligand (two imine and two oxime N atoms) form the base of the pyramid, with a water mol­ecule at an apex. The two parts of the dimer are linked by an interaction [2.869,(2),Å] between one of the Cu atoms and one of the oxime O atoms coordinated to the second Cu atom, and also by a hydrogen bond between the apical water mol­ecule on the second Cu atom and the pyridyl N atom from the coordination sphere of the first Cu atom. The pyridyl N atoms of the lariat arms are not coordinated to either of the Cu atoms. Thus, this potentially pentadentate ligand is only tetradentate when coordinated to CuII. [source]

catena -Poly[[bis(cis -1- tert -butyltetrazole-,N4)copper(II)]-di-,-chloro]

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2002
Dmitry O. Ivashkevich
The title polymeric compound, [CuCl2(C5H10N4)2]n, is the first structurally characterized complex with a bulky 1-alkyl­tetrazole ligand. The coordination polyhedron of the Cu atom is an elongated octahedron. The equatorial positions of the octahedron are occupied by the two Cl atoms, with Cu,Cl distances of 2.2920,(8) and 2.2796,(9),Å, and by the two N-4 atoms of the tetrazole ligands, with Cu,N distances of 2.023,(2) and 2.039,(2),Å. Two symmetry-related Cl atoms occupy the axial positions, at distances of 2.8244,(8) and 3.0174,(8),Å from the Cu atom. The [CuCl2(C5H10N4)2] units form infinite chains extended along the b axis, linked together only by van der Waals interactions. The skeleton of each chain consists of Cu and Cl atoms. [source]

Tetra­aqua(5-fluoro­uracil-1-acetato- O)copper(II) tetra­hydrate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2000
Jian Huang
In the title complex, [Cu(C6H4FN2O4)2(H2O)4]·4H2O, the Cu atom is located in the centre of a distorted octahedral geometry. The coordination atoms are six O atoms provided by two carboxyl­ate groups [coordinated in a monodentate mode, with Cu,O = 1.9551,(10),Å] and four water mol­ecules [Cu,O = 1.9241,(13) and 2.5771,(14),Å]. In addition, one intramolecular hydrogen bond and ten intermolecular hydrogen bonds make up a three-dimensional network. [source]

X-ray structure of the NO-bound CuB in bovine cytochrome c oxidase

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2010
Kazuhiro Ohta
The X-ray crystallographic structure of nitric oxide-treated bovine heart cytochrome c oxidase (CcO) in the fully reduced state has been determined at 50,K under light illumination. In this structure, nitric oxide (NO) is bound to the CcO oxygen-reduction site, which consists of haem and a Cu atom (the haem a3,CuB site). Electron density for the NO molecule was observed close to CuB. The refined structure indicates that NO is bound to CuB in a side-on manner. [source]

The copper-containing amine oxidase from Arthrobacter globiformis: refinement at 1.55 and 2.20,Å resolution in two crystal forms

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2006
David B. Langley
Copper-containing amine oxidases are found in all the major kingdoms of life. They catalyse the oxidation of organic amines in the presence of molecular dioxygen to aldehydes and hydrogen peroxide. The catalytic centres contain a Cu atom and a topaquinone cofactor formed autocatalytically from a tyrosine residue in the presence of Cu and molecular oxygen. The structure of the Cu-containing amine oxidase from Arthrobacter globiformis, which was previously refined at 1.8,Å resolution in space group C2 with unit-cell parameters a = 157.84, b = 63.24, c = 91.98,Å, , = 112.0° [Wilce et al. (1997), Biochemistry, 36, 16116,16133], has been re-refined with newly recorded data at 1.55,Å resolution. The structure has also been solved and refined at 2.2,Å resolution in a new crystal form, space group C2, with unit-cell parameters a = 158.04, b = 64.06, c = 69.69,Å, , = 111.7°. [source]

Synthesis, Crystal Structures and Thermal Stabilities of [Cu(bpp)2(bpdc)(H2O)2]n·2nH2O and [Cu(bpp)2]n·n (tdc) ·7.5nH2O

CHINESE JOURNAL OF CHEMISTRY, Issue 10 2008
Jing-Hua YU
Abstract Two novel copper(II) coordination polymers [Cu(bpp)2(bpdc)(H2O)2]n·2nH2O (1) and [Cu(bpp)2]n·n(tdc)·7.5nH2O (2) (H2bpdc=biphenyl-4,4,-dicarboxylic acid, bpp=1,3-di(4-pyridyl)propane and H2tdc=thiophene-2,5-dicartboxylic acid) have been synthesized by the reactions of Cu(NO3)2 and bpp with the H2bpdc or H2tdc, respectively at room temperature. In the complexes 1 and 2, their Cu atoms have a distorted octahedral geometry, and two water molecules coordinate weakly to the Cu atom in the long axial direction. Both complexes have one-dimensional linear polymer structures. In complex 1, both carboxylate groups of the bpdc can coordinate to Cu atom, while both carboxylate groups of the tdc dianion in complex 2 do not coordinate to the Cu atom, which only balance the charge. In the both complexes, the bpp ligand has different conformation: trans - trans in complex 1 and trans - gauche in complex 2. The thermal gravimetric analyses indicate that both complexes are stable under 110 and 160 °C, respectively. [source]

Void formation in the Cu layer during thermal treatment of SiNx/Cu/Ta73Si27/SiO2/Si systems

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 1-2 2005
R. Hübner
Abstract The thermal stability of a SiNx passivation layer and its influence on the annealing behavior of an amorphous Ta73Si27 diffusion barrier deposited between copper and SiO2 were analyzed by X-ray diffraction, glow discharge optical emission spectroscopy, Auger electron spectroscopy, scanning electron microscopy, and transmission electron microscopy. During heat treatment at a temperature Tan = 500 °C, diffusion of Cu atoms out of the Cu metallization into the SiNx passivation occurs. The Cu diffusion intensifies with increasing annealing temperature and annealing time and seems to be a necessary precondition for a defect formation process observed within the Cu metallization. Depending on the chemical composition of the SiNx/Cu interface, voids in the ,m-range can be formed within the Cu film. Compared to an unpassivated sample, heat treatment leads to a reduced diffusion of Ta atoms from the barrier through the copper into the SiNx/Cu interface. The barrier crystallization process into Ta5Si3 occurring during annealing at Tan = 600 °C is principally not affected by the presence of a SiNx passivation. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Tuning of Copper(I),Dioxygen Reactivity by Bis(guanidine) Ligands,

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2005
Sonja Herres-Pawlis
Abstract A series of bis(guanidine) ligands designed for use in biomimetic coordination chemistry, namely bis(tetramethylguanidino)-, bis(dipiperidinoguanidino)-, and bis(dimethylpropyleno)propane (btmgp, DPipG2p and DMPG2p, respectively), has been extended to include bis(dimethylethyleneguanidino)propane (DMEG2p), which has both Namine atoms of each guanidine functionality connected by a short ethylene bridge, as a member. From this series, a family of novel bis(guanidine)copper(I) compounds , [Cu2(btmgp)2][PF6]2 (1), [Cu2(DPipG2p)2][PF6]2 (2), [Cu2(DMPG2p)2][PF6]2 (3), and [Cu2(DMEG2p)2][PF6]2·2MeCN (4) , has been synthesised. Single-crystal X-ray analysis of 1,4 demonstrated that these compounds contain dinuclear complex cations that contain twelve-membered heterocyclic Cu2N4C6 rings with the Cu atoms being more than 4 Å apart. Each copper atom is surrounded by a set of two N-donor functions from different ligands, resulting in linear N,Cu,N coordination sites. Depending on their individual substitution patterns, the guanidine moieties deviate from planarity by characteristic propeller-like twists of the amino groups around their N,Cimine bonds. The influence of these groups on the reactivity of the corresponding complexes 1,4 with dioxygen was investigated at low temperatures by means of UV/Vis spectroscopy. The reaction products can be classified into ,-,2:,2 -peroxodicopper(II) or bis(,-oxo)dicopper(III) complex cations that contain the {Cu2O2}2+ core portion as different isomers. The electronic properties of the specific bis(guanidine) ligands are discussed from the viewpoint of their ,-donor and ,-acceptor capabilities, and it is shown that ,-,2:,2 -peroxodicopper(II) complexes are stabilised relative to the bis(,-oxo)dicopper(III) ones if , conjugation within the guanidine moieties is optimised. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Hydrodenitrification with PdCu Catalysts: Catalyst Optimization by Experimental and Quantum Chemical Approaches

ISRAEL JOURNAL OF CHEMISTRY, Issue 1 2006
Irena Efremenko
A continuous process for nitrate and nitrite abatement from drinking water by catalytic hydrogenation has been developed in our lab. We describe the experimental process development procedure, and support it with semiempirical quantum chemical methods. Comparisons of activated carbon (ACC) and silica glass fiber (GFC) cloths as supports for mono- and bimetallic Pd-Cu catalysts show the former to be 45-fold and 15-fold more active for nitrite and nitrate hydrogenation, respectively, than the latter. Catalysts prepared by selective deposition of Cu on Pd/ACC led to better activity for nitrate hydrogenation than catalysts prepared by co-impregnation or ion exchange methods. The optimal Cu:Pd atomic ratio was found to be 1:2. The computational results show the following: (i) The dispersion of Pd catalysts supported on ACC is much higher than that on GFC due to the larger surface area and higher density of adsorption sites, and that accounts for the higher activity of PdCu/ACC; (ii) Nanosized Pd particles supported on ACC have a semispherical shape and possess preferentially close-packed triangular surfaces, while Pd/GFC particles are extended in the direction parallel to the support surface and show both fcc (100) and (111) planes; (iii) The interaction of Cu atoms with both supports is stronger than that of Pd; adsorbed Cu atoms show a greater ability to form monometallic than bimetallic bonds and that should result in poor mixing of the metal upon co-impregnation, as was observed experimentally; (iv) Cu atoms in bimetallic PdCu particles admit a significant positive charge; the experimentally measured solubility of metal atoms correlates with their calculated charges. The best catalyst (2 wt%Pd-0.6 wt%Cu/ACC) was employed in a novel continuous flow reactor for nitrate hydrogenation in distilled and tap water. The advantages of the reactor investigated over a conventional packed bed reactor are discussed, suggesting a potential for further process intensification. [source]

A comparative ab initio study of Cu overlayers on BaTiO3(001) and MgO(001) substrates

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2008
Yu. F. Zhukovskii
Abstract In order to compare Cu adhesion upon two kinds of perfect cubic (001) oxide surfaces: (i) TiO2 - and BaO-terminated substrates of partly covalent BaTiO3 and (ii) highly ionic MgO substrate, we have performed DFT-LCAO calculations using a hybrid B3PW Hamiltonian. 2D symmetrical slabs used here contain seven BaTiO3 and five MgO substrate layers covered on both sides by submonolayers of ordered Cu atoms. The Cu periodic coverage density atop the surface oxygen anions was varied from 1/8 to 1/2 monolayer. Copper bonding on the BaTiO3(001) surface has been found to be noticeably stronger than that on ionic MgO(001). Cu adatoms attract the electron density from BaO-terminated and donate it towards TiO2 -terminated BaTiO3(001) substrates, respectively, by an amount that is about threefold larger than for a Cu/MgO(001) interface. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Electronic structure studies of DyNi4Cu

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2006
M. Pugaczowa-Michalska
Abstract Electronic structure of the DyNi4Cu compound, crystallising in the hexagonal CaCu5 -type of structure has been studied using the XPS method as well as the self-consistent spin-polarised TB-LMTO (tigh-binding linear muffin-tin orbital) method. Our calculations show that DyNi4Cu is ferromagnetically ordered at 0 K. The analysis of the valence band shape in vicinity of the Fermi level shows that this part of the spectrum comes mainly from 3d electrons of Ni and Cu atoms. The features of the experimental XPS valence band spectra near the Fermi level are reproduced in our calculations. Peaks below ,7.5 eV are connected with the contribution of the f -electrons of Dy. The obtained peak positions in the valence band are in good agreement with the binding energies of metallic dysprosium, copper and nickel. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Polymorphism and piezochromicity in the three-dimensional network-based phosphate RbCuPO4

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2010
Paul F. Henry
Rubidium copper phosphate, RbCuPO4, forms two room-temperature polymorphs that have been investigated with neutron powder diffraction. Polymorph (II) can be converted quantitatively into (I) by grinding the material or by pelletization, and the phase transition is accompanied by a significant colour change from very pale green to sky blue. Polymorph (II) can be obtained essentially free of (I) by quenching from 723,K. Each polymorph shows two unique Cu atoms: in (I) both sites are four-coordinate in a 2:1 ratio, whereas in (II) the atoms are four- and five-coordinate in a 1:1 ratio. In each case these sites are linked by phosphate tetrahedra to form three-dimensional frameworks based on the 42638- a four-connected net. The Rb atoms are hosted in the six- and eight-ring channels that are similar to those observed in zeolite ABW. The (II) , (I) phase transition is also accompanied by a volume reduction of 2.1% even though the average coordination of the Cu atoms also falls. The structures of the polymorphs are critically examined and compared with those of KNiPO4 and KCuPO4 in terms of hexagonal close packing containing ordered phosphate arrays. As a result of buckling of the six-ring layers, one-dimensional chains of dimerized copper polyhedra are identified in (II), chains that become trimers with mirror symmetry in (I). [source]

Klockmannite, CuSe: structure, properties and phase stability from ab initio modeling

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 3-2 2002
Victor Milman
The details of the electronic and crystal structure, the nature of the interatomic bonding and the phase stability of three modifications of klockmannite, CuSe, are analysed using first principles modeling. The hexagonal modification of CuSe is predicted to be less stable than the orthorhombic phase under pressure. The stabilizing force for the orthorhombic phase is identified as the Cu,Cu bond formation between the Cu atoms in the flat hexagonal CuSe layer and in the buckled Cu2Se2 layer. Furthermore, klockmannite is shown to be unstable under compression with respect to the decomposition into umangite, Cu3Se2, and krutaite, CuSe2 II. [source]

Copper(II) chloride and bromide complexes with 2-methyl-2H -tetrazol-5-amine: an X-ray powder diffraction study

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010
Ludmila S. Ivashkevich
The complex catena -poly[[dibromidocopper(II)]-bis(,-2-methyl-2H -tetrazol-5-amine)-,2N4:N5;,2N5:N4], [CuBr2(C2H5N5)2]n, (I), and the isotypic chloride complex catena -poly[[dichloridocopper(II)]-bis(,-2-methyl-2H -tetrazol-5-amine)-,2N4:N5;,2N5:N4], [CuCl2(C2H5N5)2]n, (II), were investigated by X-ray powder diffraction at room temperature. The crystal structure of (I) was solved by direct methods, while the Rietveld refinement of (II) started from the atomic coordinates of (I). In both structures, the Cu atoms lie on inversion centres, adopting a distorted octahedral coordination of two halogen atoms, two tetrazole N atoms and two 5-amine group N atoms. Rather long Cu,Namine bonds allow consideration of the amine group as semi-coordinated. The compounds are one-dimensional coordination polymers, formed as a result of 2-methyl-2H -tetrazol-5-amine ligands bridging via a tetrazole N atom and the amine N atom. In the polymeric chains, adjacent Cu atoms are connected by two such bridges. [source]

(+ac,,ac)- trans -Bis(hinokitiolato)copper(II) and its chloroform disolvate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2009
Douglas M. Ho
The complex trans -bis(hinokitiolato)copper(II) [systematic name: trans -bis(3-isopropyl-7-oxocyclohepta-1,3,5-trienolato)copper(II); abbreviated name: trans -Cu(hino)2], [Cu(C10H11O2)2], is a biologically active compound. Three polymorphs of this square-planar monomer, all with (+sp,,sp) isopropyl substituents, have been reported previously. A fourth polymorph containing (+ac,,ac) isopropyl groups and its chloroform disolvate, [Cu(C10H11O2)2]·2CHCl3, both exhibiting nonmerohedral twinning and with all Cu atoms on centers of crystallographic inversion symmetry, are reported here. One of the differences between all of these polymorphs is the relative conformation of the isopropyl groups with respect to the plane of the molecule. Stacking and Cu...olefin , distances ranging from 3.214,(4) to 3.311,(2),Å are observed, and the chloroform solvent molecules participate in bifurcated C,H...O hydrogen bonds [H...O = 2.26,2.40,Å, C...O = 3.123,(5),3.214,(5),Å, C,H...O = 127,151° and O...H...O = 74°]. [source]

Dicopper(II) trihydroxide cyanoureate dihydrate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2009
Ann M. Chippindale
The title compound, poly[[,-cyanoureato-tri-,-hydroxido-dicopper(II)] dihydrate], {[Cu2(C2H2N3O)(OH)3]·2H2O}n, is a new layered copper(II) hydroxide salt (LHS) with cyanoureate ions and water molecules in the interlayer space. The three distinct copper(II) ions have distorted octahedral geometry: one Cu (symmetry ) is coordinated to six hydroxide groups (4OH + 2OH), whilst the other two Cu atoms (symmetries and 1) are coordinated to four hydroxides and two N atoms from nitrile groups of the cyanoureate ions (4OH + 2N). The structure is held together by hydrogen-bonding interactions between the terminal ,NH2 groups and the central cyanamide N atoms of organic anions associated with neighbouring layers. [source]