State For Cu Research Articles

Controlled Synthesis, Characterization and Magnetic Properties of Unsymmetrical Heterodinuclear CuIIMII (M = Co, Mn and Cd) Complexes in Alkoxo Bridged Acyclic Ligand Environment

This work reports the syntheses of heterodinuclear Cu(II)-Co(II), Cu(II)-Mn(II) and Cu(II)-Cd(II) complexes following a convenient single-pot synthetic procedure using the two asymmetric binucleating ligands. Site-specificity offered by one of the ligands' arms towards Cu(I) center has been successfully exploited here, avoiding all sorts of impending scrambling reactions. X-ray crystallography and ESImass spectral studies have been used to prove the exclusivity of these products. Magnetic studies at variable temperatures (4-300 K) have been proved inadequate to assign any spin-ground state for Cu(II)-Co(II) and Cu(II)-Mn(II) compounds.

Effect of iron oxidation state for copper recovery from nickel laterite leach solution using chelating resin

ABSTRACTThe goal of this work was to study the effect of iron oxidation state for Cu(II) recovery. Two different solutions of nickel laterite leach were prepared with Fe(III) and with Fe(II) for the experiments. FTIR of the chelating resin were analyzed before and after metals adsorption. Kinetics and thermodynamics of metals adsorption were studied in batch. Column experiments were performed to study the effect of iron oxidation state on Cu(II) adsorption. Results indicated that Cu(II) recovery was strongly related to iron oxidation state. Cu(II) adsorption was higher in solution with Fe(II) than with Fe(III). Temperature decreased Cu(II) adsorption. Column experiments showed that Fe(II) reached rapidly the equilibrium during the feeding step, and it was lower adsorbed than Fe(III).

Coordination Behavior of N‐Donor Schiff Base Derived from 2‐Benzoylpyridine Toward Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Pd(II), and Cr(III) Metal Ions: Synthesis, Spectroscopic and Thermal Studies, and Biological Activity

A new Schiff base was prepared from the reaction of 4,4′‐methylenedianiline with 2‐benzoylpyridine in 1:2 molar ratio, as well as its different metal chelates. The structures of the ligand and its metal complexes were studied by elemental analyses, spectroscopic methods (infrared [IR], ultraviolet–visible [UV–vis], 1H nuclear magnetic resonance [NMR], electron spin resonance [ESR]), magnetic moment measurements, and thermal studies. The ligand acts as tetradentate moiety in all complexes. Octahedral geometry was suggested for Mn(II), Cu(II), Cr(III), and Zn(II) chloride complexes and pentacoordinated structure and square planar geometry for Co(II), Ni(II), Cu(NO3 )2, CuBr2 , and Pd(II) complexes. ESR spectra of copper(II) complexes (4)–(6) at room temperature display rhombic symmetry for complex (4) and axial type symmetry for complexes (5) and (6), indicating ground state for Cu(II) complexes. The derivative thermogravimetric (DTG) curves of the ligand and its metal complexes were analyzed by using the rate equation to calculate the thermodynamic and kinetic parameters, which indicated strong binding of the ligand with the metal ion in some complexes. Also, some of these compounds were screened to establish their potential as anticancer agents against the human hepatic cell line Hep‐G2 . The obtained IC50 value of the copper(II) bromide complex (4.34 µg/mL) is the highest among the compounds studied.

N–H and S–H insertions over Cu(I)-zeolites as heterogeneous catalysts

N–H and S–H insertion reactions of α-diazoesters into amines and thiols were conducted using various Cu(I)-zeolites, such as zeolite Y, Y USY, ZSM-5, and beta. All the Cu(I)-zeolites successfully catalyzed N–H insertion reactions with high product yields (70–82%) in aqueous solution at room temperature. Interestingly, Cu(I)-USY (Si/Al=30) showed better activity for both N–H and S–H insertion reactions than Cu(I)-Y (Si/Al=2.6), even though they have the same structure and the same +1 oxidation state for Cu. X-ray diffraction, transmission electron microscopy, and X-ray photoemission spectroscopy analysis of the fresh and used catalysts revealed that no noticeable change in the zeolite structure, oxidation state of Cu, or sintering of Cu occurred during the reactions. Furthermore, after being recycled four times, the catalysts showed only minor activity decreases, exhibiting conversion rates 70–80% of those of the fresh catalysts, demonstrating their stability under the current reaction conditions. Temperature programmed reduction experiments showed that reduction of Cu+ to Cu° occurred at ca. 300°C over Cu(I)-USY, while it occurred at ca. 800°C over Cu(I)-Y. The significantly higher activity of Cu(I)-USY than Cu(I)-Y may be due to the more electrophilic Cu centers on Cu(I)-USY, which is highly favorable for ylide formation, and therefore facilitates N–H and S–H insertions.

Generation of converging strong shock wave formed by microsecond timescale underwater electrical explosion of spherical wire array

A study of generation of converging strong shock wave using microsecond underwater electrical explosion of spherical Cu-wire array is presented. Hydrodynamic simulations coupled with the equation of state for Cu and water, deposited energy, and the magnetic pressure were used to calculate the water parameters in the vicinity of the implosion origin. The results of simulations agree with the shock wave time-of-flight and energy delivered to the water flow and show that in the vicinity (diameter of ∼12 μm) of an implosion one can expect water pressure of ∼6 TPa, temperature of ∼17 eV, and compression of ∼8.

Equations of state for Cu, Ag, and Au and problems with shock wave reduced isotherms

Thermophysical data at low pressure are used to constrain a thermodynamic model for equations of state and all the other thermophysical properties in wide ranges of pressure and temperature. Comparisons with shock wave reduced isotherms show strong deficiencies in the models used in the data reductions. A revision in the evaluation of static high-pressure X-ray diffraction data for Cu and Au together with data for ruby luminescence line shifts from the literature lends further support to some recent refinements of the ruby pressure scale.

The unusual magnetic properties of kuramite–stannite pseudobinary series: a SQUID and EPR survey

The magnetic properties of the synthetic Cu3SnS4 (kuramite)–Cu2FeSnS4 (stannite) pseudobinary series were investigated by means of electron paramagnetic resonance (EPR) spectroscopy, at room temperature, and by magnetometry, in the range 2–300 K. The system is particularly complex, from both chemical and crystal chemical points of view, in particular with respect to the metal valence states and the local ordering in the different terms of the series. Nevertheless, recent successes in synthesising nanostructured kuramite foster the interest to ascertain the bulk magnetic properties of these important semiconducting phases. The obtained results allowed to ascertain that a variable lack of local ordering in the Cu3–x Fe x SnS4 (x < 0.85) samples induce the raise of strong metal–sulphur–metal superexchange interactions, that result in the appearance of marked deviations from the single-ion behaviour, typical for pure stannite. Ferro- and antiferromagnetic interactions are in fact observed at relatively high temperatures (~150 K). A possible role played by Cu(I)–Fe(III) was revealed by the EPR measurements. The Cu-rich terms of the series (x < 0.1) are characterised by dynamic resonant disorder (i.e. time-evolving delocalisation of the formally divalent valence state for Cu among the nearest neighbouring Cu-sites), in addition to the Cu–Fe–Sn static disorder verified along the whole series. Both factors concurring to a non-periodic arrangement of paramagnetic ions in the lattice have the main effect to drastically broaden the EPR lines.

Refined equations of state for Cu, Ag, and Au in the sub-TPa region

The Equations of State for Cu, Ag, and Au in the sub-TPa region are constraint by correlated fits of all the thermo-physical data at ambient pressure and by theoretical estimates of the intrinsic anharmonicities. A hierarchy in the parameters provides a robust fitting procedure with typical accuracies of the finally calculated pressures of probably better than 1% at temperatures to the melting curve and pressures into the TPa-region.

Laser-launched flyer plates for shock physics experiments

The TRIDENT laser was used to launch Cu, Ga, and NiTi flyers from poly(methylmethacrylate) (PMMA) substrates, coated with thin (∼micron) layers to absorb the laser energy, confine the plasma, and insulate the flyer. The laser pulse was ∼600ns long, and the flyers were 50 to 250μm thick and 4 mm in diameter. With an energy of 10–20 J, speeds of several hundred meters per second were obtained. Simulations were performed of the flyer launch process, using different models. The simulations reproduced the magnitude of the flyer speed and qualitative variations with drive energy and design parameters, but systematically overpredicted the flyer speed. The most likely explanation is that some of the laser energy was deposited in the transparent substrate, reducing the amount available for acceleration. The deceleration of the flyer was measured on impact with a PMMA window. Given the equation of state and optical properties of PMMA, the deceleration allowed points to be deduced on the principal Hugoniot of Cu. The points deduced were in good agreement with the published equation of state for Cu, suggesting that there was no significant preheating of the flyer or other systematic effects which might reduce the accuracy of equation of state measurements.

EPR of Cu 2+ and VO 2+ in a cobalt saccharin complex, [Co(sac) 2(H 2O) 4]·2H 2O, single crystals

Cu 2+ and VO 2+ doped single crystals of [Co(sac) 2(H 2O) 4]·2H 2O (Cosacaqua) complex were investigated using EPR technique at ambient temperature. Detailed investigation of the EPR spectra indicated that the Cu 2+ and VO 2+ substitute the Co 2+. Two sites were observed for Cu 2+ and VO 2+. But each site of V 4+ corresponds two different orientations of VO 2+. The principal values of the g and the hyperfine tensors were obtained. The spectra indicate that the ground state for Cu 2+ is mainly 3 d x 2− y 2 . The covalent bonding parameters for Cu 2+ and VO 2+ and Fermi contact terms were obtained.

Static and vibrational properties of transition metals

A model pseudopotential depending on an effective core radius but otherwise parameter free is proposed to study the equation of state by incorporating the s-d hybridization effects. Very recently proposed screening function due to Sarkar et al has been used to obtain the screened form factor. The equations of state for Cu, Ta, Mo, W and Pt have been studied up to the pressure of 1000 GPa. The vibrational properties such as phonon dispersion curves (in q and r space), phonon density of states, mode Gruneisen parameters, maximum frequency ωmax, mean frequency 〈ω〉, 〈ω2〉1/2 = (〈ω〉/ 〈ω-1〉)1/2 and fundamental frequency 〈ω2〉 and static properties such as dynamical elastic constants of rhodium and iridium are also calculated. The theoretical results are compared with experimental findings wherever possible. A good agreement between theoretical investigations and experimental findings has confirmed our formulation.

Equations of State for Cu, Ag, and Au for Wide Ranges in Temperature and Pressure up to 500 GPa and Above

New constraints on the volume dependence of the Grüneisen parameter (γ(V)) are derived from a comparison of earlier shock wave data with more recent ultrasonic data for the bulk modulus K0 and its pressure derivative K0′ in the frame of a rigorous Mie–Grüneisen model. This model uses a specially “Modified pseudo-Debye–Einstein model” for an accurate representation of the thermal energy and pressure. Within this framework, previous discrepancies between shock wave and static data concerning the equations of state for various reference materials (like Cu, Ag, and Au) are resolved, the corresponding pressure scale is refined, and the uncertainties in this scale are estimated.

Crystallographic determination of reduced bovine superoxide dismutase at pH 5.0 and of anion binding to its active site

The crystal structures of dithionite-reduced bovine Cu(I),Zn superoxide dismutase and of its adducts with the inorganic anions azide and thyocyanide have been determined in a C2221 crystal form obtained at pH 5.0. This crystal form is characterized by a high solvent content (72%) and by having the two Cu,ZnSOD monomers (A and B) in different crystal environments. One of them (B) is involved in few intermolecular crystal contacts so that it is in a more "solution like" environment, as indicated by average temperature factors which are about twice those of the other monomer. The differences in crystal packing affect the active site structures. While in the A monomer the Cu(I) is coordinated to all four histidine residues, in the B monomer the bridging His61 side chain is found disordered, implying partial detachment from copper. The same effect occurs in the structures of the anion complexes. The inorganic anions are found bound in the active site cavity, weakly interacting with copper at distances ranging from 2.5 to 2.8 A. The copper site in the A subunit of the native enzyme structure displays significant electron density resembling a diatomic molecule, bound side-on at about 2.8 A from the metal, which cannot be unambiguously interpreted. The crystallographic data suggest that the existence of the His61 bridge between copper and zinc is dominated by steric more than electronic factors and that the solution state favors the His61 detachment. These structures confirm the existence of an energetically available state for Cu(I) in Cu,ZnSOD where the histidinato bridge to zinc is maintained. This state appears to be favored by tighter crystal contacts. The binding of the anions in the active site cavity is different from that observed in the oxidized enzyme and it appears to be dominated by electrostatic interactions within the cavity. The anion binding mode observed may model the substrate interaction with the reduced enzyme during catalysis.

Zeeman spectroscopy of neutral copper in germanium

The results of high field Zeeman spectroscopy of the D line of neutral copper (Cu (0)) acceptors in Ge are presented. It is found that the excited state of this transition has a splitting which is identical to that observed for this same transition for group III impurities, demonstrating that the excited state for Cu (0) is the product state whose symmetry is 1 Γ 1 + × 2 Γ 8 − of O h . Similar results are obtained for the G line. The ground state g-factors have the values −0.04±0.01 and +0.30±0.01 for g′ 1 and g′ 2, respectively.

Edge state and terrace state for Cu on W(331) and W(110).

Edge state and terrace state for Cu on W(331) and W(110).

Electron spin resonance studies on some copper(II) complexes with a few nitrogen donors derived from pyridine

Abstract Electron spin resonance spectral studies have been made on copper(II) chloride, bromide, thiocyanate and sulphate complexes with some pyridine derivatives, viz. nicotinic acid (NA), nicotinamide (NICA) and isonicotinamide (INA) in solid and DMF-solution states to see the effect of different anions on the Spin-Hamiltonian parameters at the paramagnetic site for a particular ligand. The spectra of the complexes for a particular anion are almost comparable suggesting the same local symmetry for them. Analysis of the ESR data reveals axial symmetry for all the complexes, except Cu(NA) 2 SO 4 for which a rhombic symmetry is suggested. The study shows the interaction of solvent (DMF) molecules with copper(II) ion in the axial plane as evident from the differences in 295 and 77 K g | values. Moreover, the spectra are consistent with the complete absence or negligbly small copper(II)—copper(II) interactions (in few cases) in these complexes. The various Spin-Hamiltonian parameters calculated from ESR data indicate the presence of an unpaired electron in the d x 2 − y 2 orbital of the copper(II) ion with the additional possibility of a d xy ground state for Cu(NA) 2 SO 4 .

Observation of superconductivity in (Y 1− xCa x)Ba 2Cu 3O 6

Substitution of Ca 2+ for Y 3+ in YBa 2Cu 3O 6 converts this tetragonal semiconductor into a tetragonal superconductor with a T c of 50 K. Furthermore, the structure of (Y 0.8Ca 0.2)Ba 2Cu 3O 6, determined by neutron powder diffraction, is fully consistent with partial oxidation of the Cu(2) O sheets, whereas the linear O Cu(1) O units do not undergo oxidation. Observation of a limited solid solubility for Ca 2+ in this structure is attributed to a maximum allowed oxidation state for Cu(2). This implies that in the superconductor YBa 2Cu 3O 7 the Cu O chains are responsible for the T c of 90 K, whereas the Cu O sheets alone produce superconductivity at 50 K in YBa 2Cu 3O 6.5.

Auger lineshape analysis

Abstract Auger transitions occurring at solid surfaces give spectra containing information on the energy distribution of valence electrons involved in the transition. Thus Auger Electron Spectroscopy (AES) can be used as a valence band (VB) Spectroscopy that is surface sensitive. Analyses of a number of core-valence-valence (CVV) Auger spectra are reviewed to illustrate the VB information contained in their lineshapes and to indicate current understanding of the physics of the Auger process as it applies to solids. The KVV spectrum from elemental beryllium is an example of a CW line that can be analyzed simply in terms of the sum of convolution products of independent-particle VB density-of-states (DOS) components. Other elemental solids for which such simple arguments suffice include Al, Si, Li, Ti, Co and B. The CW spectra from copper are discussed as examples of CW lineshapes that are distorted from those expected from simple VB DOS arguments because localization in the two-hole Auger final state for Cu makes hole-hole interactions important in determining the Auger lineshapes. Initial state screening is shown to influence the CVV lineshapes from Be as well as Cu. CVV spectra from the compound surfaces BeO and SiO2 are analyzed using concepts of interatomic transitions as well as independent-parsite. ticle VB arguments. These spectra show that AES is a probe of the local DOS about the core-hole This ability of AES to give local bonding information is illustrated by analyses of CW spectra from multi-component surfaces which may be made in terms of the simple superposition of local-bonding signals. Thus the Si-L23VV signal from silicon oxynitride is shown to be the superposition of signals representing elemental Si, Si-H, Si-N and Si-O bonding.

Auger lineshape analysis

Auger transitions occurring at solid surfaces give spectra containing information on the energy distribution of valence electrons involved in the transition. Thus Auger Electron Spectroscopy (AES) can be used as a valence band (VB) Spectroscopy that is surface sensitive. Analyses of a number of core-valence-valence (CVV) Auger spectra are reviewed to illustrate the VB information contained in their lineshapes and to indicate current understanding of the physics of the Auger process as it applies to solids. The KVV spectrum from elemental beryllium is an example of a CW line that can be analyzed simply in terms of the sum of convolution products of independent-particle VB density-of-states (DOS) components. Other elemental solids for which such simple arguments suffice include Al, Si, Li, Ti, Co and B. The CW spectra from copper are discussed as examples of CW lineshapes that are distorted from those expected from simple VB DOS arguments because localization in the two-hole Auger final state for Cu makes hole-hole interactions important in determining the Auger lineshapes. Initial state screening is shown to influence the CVV lineshapes from Be as well as Cu. CVV spectra from the compound surfaces BeO and SiO 2 are analyzed using concepts of interatomic transitions as well as independent-parsite. ticle VB arguments. These spectra show that AES is a probe of the local DOS about the core-hole This ability of AES to give local bonding information is illustrated by analyses of CW spectra from multi-component surfaces which may be made in terms of the simple superposition of local-bonding signals. Thus the Si-L 23VV signal from silicon oxynitride is shown to be the superposition of signals representing elemental Si, Si-H, Si-N and Si-O bonding.

5023. Auger analysis of surface deposits formed by exposure to plasma discharges in Doublet III: J N Smith Jr and C H Meyer Jr, J Vac Sci Technol, 19 (1), 1981, 63–71

Auger transitions occurring at solid surfaces give spectra containing information on the energy distribution of valence electrons involved in the transition. Thus Auger Electron Spectroscopy (AES) can be used as a valence band (VB) Spectroscopy that is surface sensitive. Analyses of a number of core-valence-valence (CVV) Auger spectra are reviewed to illustrate the VB information contained in their lineshapes and to indicate current understanding of the physics of the Auger process as it applies to solids. The KVV spectrum from elemental beryllium is an example of a CW line that can be analyzed simply in terms of the sum of convolution products of independent-particle VB density-of-states (DOS) components. Other elemental solids for which such simple arguments suffice include Al, Si, Li, Ti, Co and B. The CW spectra from copper are discussed as examples of CW lineshapes that are distorted from those expected from simple VB DOS arguments because localization in the two-hole Auger final state for Cu makes hole-hole interactions important in determining the Auger lineshapes. Initial state screening is shown to influence the CVV lineshapes from Be as well as Cu. CVV spectra from the compound surfaces BeO and SiO2 are analyzed using concepts of interatomic transitions as well as independent-parsite. ticle VB arguments. These spectra show that AES is a probe of the local DOS about the core-hole This ability of AES to give local bonding information is illustrated by analyses of CW spectra from multi-component surfaces which may be made in terms of the simple superposition of local-bonding signals. Thus the Si-L23VV signal from silicon oxynitride is shown to be the superposition of signals representing elemental Si, Si-H, Si-N and Si-O bonding.