Temperature dependence of the crystal structure and g-values of [(HC(Ph2PO)(3))(2)Cu] (ClO4)(2)center dot 2H(2)O: Influence of dynamic Jahn-Teller coupling and lattice strain interactions

The temperature dependence of the X-ray crystal structure and powder EPR spectrum of [(HC(Ph2PO)(3))(2)CU]-(ClO4)(2)center dot 2H(2)O is reported, and the structure at room temperature confirms that reported previously. Below similar to 100 K, the data imply a geometry with near elongated tetragonal symmetry for the [(HC(Ph2PO)(3))(2)Cu](2+) complex, but on warming the two higher Cu-O bond lengths and g-values progressively converge, and by 340 K the bond lengths correspond to a compressed tetragonal geometry. The data may be interpreted satisfactorily assuming an equilibrium among the energy levels of a Cu-O-6 polyhedron subjected to Jahn-Teller vibronic coupling and a lattice strain. However, agreement with the experiment is obtained only if the orthorhombic component of the lattice strain decreases to a negligible value as the temperature approaches 340 K.

The effect of copper toxicity on the growth and root morphology of Rhodes grass (Chloris gayana Knuth.) in resin buffered solution culture

A solution culture experiment was conducted to examine the effect of Cu toxicity on Rhodes grass (Chloris gayana Knuth.), a pasture species used in mine-site rehabilitation. The experiment used dilute, solution culture to achieve external nutrient concentrations, which were representative of the soil solution, and an ion exchange resin to maintain stable concentrations of Cu in solution. Copper toxicity was damaging to plant roots, with symptoms ranging from disruption of the root cuticle and reduced root hair proliferation, to severe deformation of root structure. A reduction in root growth was observed at an external Cu concentration of < 1 mu M, with damage evident from an external concentration of 0.2 mu M. Critical to the success of this experiment, in quantitatively examining the relationship between external Cu concentration and plant response, was the use of ion exchange resin to buffer the concentration of Cu in solution. After some initial difficulty with pH control, stable concentrations of Cu in solution were maintained for the major period of plant growth. The development of this technique will facilitate future investigations of the effect of heavy metals on plants.

Bajo de la Alumbrera copper-gold deposit: Stable isotope evidence for a porphyry-related hydrothermal system dominated by magmatic aqueous fluids

Alteration zones at the gold-rich Bajo de la Alumbrera porphyry copper deposit in northwestern Argentina are centered on several porphyritic intrusions. They are zoned from a central copper-iron sulfide and gold-mineralized potassic (biotite-K-feldspar +/- quartz) core outward to propylitic (chlorite-illite-epidote-calcite) assemblages. A mineralized intermediate argillic alteration assemblage (chlorite-illite +/- pyrite) has overprinted the potassic alteration zone across the top and sides of the deposit and is itself zoned outward into phyllic (quartzinuscovite-illite +/- pyrite) alteration. This study contributes new data to previously reported delta(18)O and delta D compositions of fluids responsible for the alteration at Bajo de la Alumbrera, and the data are used to infer likely ore-forming processes. Measured and calculated delta(18)O and delta D values of fluids (+8.3 to +10.2 and -33 to -81 parts per thousand, respectively) confirm a primary magmatic origin for the earliest potassic alteration phase. Lower temperature potassic alteration formed from magmatic fluids with lower delta D values (down to -123 parts per thousand). These depleted compositions are distinct from meteoric water and consistent with degassing and volatile exsolution of magmatic fluids derived from an underlying magma. Variability in the calculated composition of fluid associated with potassic alteration is explained in terms of phase separation (or boiling). if copper-iron sulfide deposition occurred during cooling (as proposed elsewhere), this cooling was largely a result of phase separation. Magmatic water was directly involved in the formation of overprinting intermediate argillic alteration assemblages at Bajo de la Alumbrera. Calculated delta(18)O and delta D values of fluids associated with this alteration range from +4.8 to +8.1 and -31 to -71 per mil, respectively Compositions determined for fluids associated with phyllic alteration (-0.8 to +10.2 and -31 to -119 parts per thousand) overlap with the values determined for the intermediate argillic alteration. We infer that phyllic alteration assemblages developed during two stages; the first was a high-temperature (400 degrees-300 degrees C) stage with D-depleted water (delta D = -66 to -119 parts per thousand). This compositional range may have resulted from magma degassing and/or the injection of new magmatic water into a compositionally evolved hydrothermal system. The isotopic variations also can be explained by increased fluid-rock interaction. The second stage of phyllic alteration occurred at a lower temperature (similar to 200 degrees C), and variations in the modeled isotopic compositions imply mixing of magmatic and meteoric waters. Ore deposition that occurred late in the evolution of the hydrothermal system was probably associated with further cooling of the magmatic fluid, in part caused by fluid-rock interaction and phase separation. Changing pH and/or oxygen fuoracity may have caused additional ore deposition. The ingress of meteoric water appears to postdate the bulk of mineralization and occurred as the system at Bajo de la Alumbrera waned.

Iron-related porosity in Al-Si-(Cu) foundry alloys

An experimental program has been undertaken to explore the effect of iron concentration on porosity levels in Al-Si alloy sand castings. The effect of iron concentrations above, below and equal to the critical iron content for alloys with either 5 or 9% Si and either 0, 1 or 3% Cu has been determined. Increasing iron concentrations were found to increase porosity in all alloys except the copper-containing Al-5% Si alloys which displayed a porosity minimum at the critical iron content. Porosity was observed to be higher in the Al-9% Si castings than the Al-5% Si castings. Differences in the primary phase volume fraction and morphology may explain this observation. The results of this experimental work do not support the existing published theories that have been proposed to explain the effect the iron on porosity. An alternative theory is therefore developed. (c) 2006 Elsevier B.V. All rights reserved.

Influence of lattice interactions on the jahn-teller distortion of the [Cu(H2O)(6)](2+) ion: Dependence of the crystal structure of K-2[Cu(H2O)(6)](SO4)(2x)(SeO4)(2-2x) upon the sulfate/selenate ratio

The temperature dependence of the structure of the mixed-anion Tutton salt K-2[Cu(H2O)(6)](SO4)(2x)(SeO4)(2-2x) has been determined for crystals with 0, 17, 25, 68, 78, and 100% sulfate over the temperature range of 85-320 K. In every case, the [Cu(H2O)(6)](2+) ion adopts a tetragonally elongated coordination geometry with an orthorhombic distortion. However, for the compounds with 0, 17, and 25% sulfate, the long and intermediate bonds occur on a different pair of water molecules from those with 68, 78, and 100% sulfate. A thermal equilibrium between the two forms is observed for each crystal, with this developing more readily as the proportions of the two counterions become more similar. Attempts to prepare a crystal with approximately equal amounts of sulfate and selenate were unsuccessful. The temperature dependence of the bond lengths has been analyzed using a model in which the Jahn-Teller potential surface of the [Cu(H2O)(6)](2+) ion is perturbed by a lattice-strain interaction. The magnitude and sign of the orthorhombic component of this strain interaction depends on the proportion of sulfate to selenate. Significant deviations from Boltzmann statistics are observed for those crystals exhibiting a large temperature dependence of the average bond lengths, and this may be explained by cooperative interactions between neighboring complexes.

Spectroscopic characterization of copper(II) binding to the immunosuppressive drug mycophenolic acid

Mycophenolic acid (MPA) is a drug that has found widespread use as an immunosuppressive agent which limits rejection of transplanted organs. Optimal use of this drug is hampered by gastrointestinal side effects which can range in severity. One mechanism by which MPA causes gastropathy may involve a direct interaction between the drug and gastric phospholipids. To combat this interaction we have investigated the potential of MPA to coordinate Cu(II), a metal which has been used to inhibit gastropathy associated with use of the NSAID indomethacin. Using a range of spectroscopic techniques we show that Cu(II) is coordinated to two MPA molecules via carboxylates and, at low pH, water ligands. The copper complex formed is stable in solution as assessed by mass spectrometry and H-1 NMR diffusion experiments. Competition studies with glycine and albumin indicate that the copper-MPA complex will release Cu(II) to amino acids and proteins thereby allowing free MPA to be transported to its site of action. Transfer to serum albumin proceeds via a Cu(MPA)(albumin) ternary complex. These results raise the possibility that copper complexes of MPA may be useful in a therapeutic situation.

Role of nanosized zirconia on the properties of Cu/Ga2O3/ZrO2 catalysts for methanol synthesis

The introduction of mesoporous nanosize zirconia to the catalyst for methanol synthesis dedicates the nanosized catalyst and mesoporous duplicated properties. The catalyst bears the larger surface area, larger mesoporous volume and more uniform diameter, more surface metal atoms and oxygen vacancies than the catalyst prepared with the conventional coprecipitation method. The modification of microstructure and electronic effect could result in the change of the reduced chemical state and decrease of reducuction temperature of copper, donating the higher activity and methanol selectivity to the catalyst. The results of methanol synthesis demonstrate that the Cu+ is the optimum active site. Also, the interaction between the copper and zirconia shows the synergistic effect to fulfil the methanol synthesis.

Atmospheric corrosion of copper and the colour, structure and composition of natural patinas on copper

This paper describes the results of atmospheric corrosion testing and of an examination of patina samples from Brisbane, Denmark, Sweden, France, USA and Austria. The aim was threefold: (1) to determine the structure of natural patinas and to relate their structure to their appearance in service and to the atmospheric corrosion of copper; (2) to understand why a brown rust coloured layer forms on the surface of some copper patinas; (3) to understand why some patinas are still black in colour despite being of significant age. During the atmospheric corrosion of copper, a two-layer patina forms on the copper surface. Cuprite is the initial corrosion product and cuprite is always the patina layer in contact with the copper. The growth laws describing patina formation indicate that the decreasing corrosion rate with increasing exposure time is due to the protective nature of the cuprite layer. The green patinas were typically characterised by an outer layer of brochantite, which forms as individual crystals on the surface of the cuprite layer, probably by a precipitation reaction from an aqueous surface layer on the cuprite layer. Natural patinas come in a variety of colours. The colour is controlled by the amount of the patina and its chemical composition. Thin patinas containing predominantly cuprite were black. If the patina was sufficiently thick, and the [Fe]/[Cu] ratio was low, then the patina was green, whereas if the [Fe]/[Cu] ratio was approximately 10 at%, then the patina is rust brown in colour. The iron was in solid solution in the brochantite, which might be designated as a (copper/iron) hydroxysulphate. In the brown patinas examined, the iron was distributed predominately in the outermost part of the patina. (c) 2005 Elsevier Ltd. All rights reserved.

Volcanic setting of the Bajo de la Alumbrera porphyry Cu-Au deposit, Farallon Negro Volcanics, Northwest Argentina

The late Miocene Farallon Negro volcanics, comprising basaltic to rhyodacitic volcano-sedimentary rocks, host the Bajo de la Alumbrera porphyry copper-gold deposit in northwest Argentina. Early studies of the geology of the district have underpinned the general model for porphyry ore deposits where hydrothermal alteration and mineralization develop in and around porphyritic intrusions emplaced at shallow depths (2.5-3.5 km) into stratovolcanic assemblages. The Farallon Negro succession is dominated by thick sequences of volcano-sedimentary breccias, with lavas forming a minor component volumetrically. These volcaniclastic rocks conformably overlie crystalline basement-derived sedimentary rocks deposited in a developing foreland basin southeast of the Puna-Altiplano plateau. Within the Farallon Negro volcanics, volcanogenic accumulations evolved from early mafic to intermediate and silicic compositions. The younger and more silicic rocks are demonstrably coeval and comagmatic with the earliest group of mineralized porphyritic intrusions at Bajo de la Alumbrera. Our analysis of the volcanic stratigraphy and facies architecture of the Farallon Negro volcanics indicates that volcanic eruptions evolved from effusive to mixed effusive and explosive styles, as magma compositions changed to more intermediate and silicic compositions. Air early phase of mafic to intermediate voleanism was characterized by small synsedimentary intrusions with peperitic contacts, and lesser lava units scattered widely throughout the district, and interbedded with thick and extensive successions of coarse-grained sedimentary breccias. These sedimentary breccias formed from numerous debris- and hyperconcentrated flow events. A later phase of silicic volcanism included both effusive eruptions, forming several areally restricted lavas, and explosive eruptions, producing more widely dispersed (up to 5 kin) tuff units, some tip to 30-m thickness in proximal sections. Four key features of the volcanic stratigraphy suggest that the Farallon Negro volcanics need not simply record the construction of a large steep-sided polygenetic stratovolcano: (1) sheetlike, laterally continuous debris-flow and other coarse-grained sedimentary deposits are dominant, particularly in the lower sections; (2) mafic-intermediate composition lavas are volumetrically minor; (3) peperites are present throughout the sequence; and (4) fine-grained lacustrine sandstone-siltstone sequences occur in areas previously thought to be proximal to the summit region of the stratovolcano. Instead, the nature, distribution, and geometry of volcanic and volcaniclastic facies suggest that volcanism occurred as a relatively low relief, multiple-vent volcanic complex at the eastern edge of a broad, > 200-km-wide late Miocene volcanic belt and oil ail active foreland sedimentary basin to the Puna-Altiplano. Volcanism that occurred synchronously with the earliest stages of porphyry-related mineralization at Bajo de la Alumbrera apparently developed in an alluvial to ring plain setting that was distal to larger volcanic edifices.

The effect of copper toxicity on the growth and morphology of Rhodes grass (Chloris gayana) in solution culture

A solution culture experiment was conducted to examine the effect of Cu toxicity on Rhodes grass (Chloris gayana), a pasture species used in mine site rehabilitation. The experiment used dilute, solution culture to achieve external nutrient concentrations which were representative of the soil solution, and ion exchange resins to maintain stable concentrations of Cu in solution. Copper toxicity was damaged plant roots, with symptoms ranging from disruption of the root cuticle and reduced root hair proliferation, to severe deformation of root structure. A reduction in root growth was observed at an external Cu concentration of

Evaluation of extractants for estimation of the phytoavailable trace metals in soils

Despite its environmental (and financial) importance, there is no agreement in the literature as to which extractant most accurately estimates the phytoavailability of trace metals in soils. A large dataset was taken from the literature, and the effectiveness of various extractants to predict the phytoavailability of Cd, Zn, Ni, Cu, and Pb examined across a range of soil types and contamination levels. The data suggest that generally, the total soil trace metal content, and trace metal concentrations determined by complexing agents (such as the widely used DTPA and EDTA extractants) or acid extractants (such as 0.1 M HCl and the Mehlich 1 extractant) are only poorly correlated to plant phytoavailability. Whilst there is no consensus, it would appear that neutral salt extractants (such as 0.01 M CaCl2 and 0.1 M NaNO3) provide the most useful indication of metal phytoavailability across a range of metals of interest, although further research is required.

New stereoselective routes to macrocyclic ligands

Reaction of bis(ethane-1,2-diamine)copper(II) with acetaldehyde and nitromethane in methanol leads, stereoselectively, to the new macrocyclic complex (trans-5(R),7(R),12(S),14(S))-tetramethyl-6,13-dinitro-1,4,8,11-tetraazacyclotetradecane)copper(II) perchlorate alpha-[CuL1](ClO4)(2) in good yield. Reduction of the nitro groups affords the hexaamine (L-2), which was crystallized as [H4L2](ClO4)(4) . 2H(2)O and characterized by an X-ray crystal structure study (monoclinic P2(1)/n, a = 9.763(2) Angstrom, b = 12.1988(7) Angstrom, c = 13.036(2) Angstrom, beta = 105.668(7)degrees, Z = 2) and complexed with Cu-II to produce the complex beta-[Cu(H2L2)](ClO4)(4) . 2H(2)O, which has also been characterized by X-ray crystallography (monoclinic P2(1)/n, a = 9.717(4) Angstrom, b = 12.174(2) Angstrom, c = 13.036(5) Angstrom, beta = 106.51(2)degrees, Z = 2). Reaction of alpha-[CuL1](2+) with either basic hydrogen peroxide or dilute nitrous acid leads to mild reduction of the nitro groups to afford the ketoxime L-3 as its N-based isomeric Cu-II complexes, trans-I [CuL3](ClO4)(2) and trans-II [Cu(L-3)Cl]Cl . 7H(2)O, the latter of which has been characterized structurally: triclinic, <P(1)over bar> a = 10.8441(5) Angstrom, b = 11.6632(9) Angstrom, c = 11.8723(9) Angstrom, alpha = 113.634(7)degrees, beta = 95.744(5), gamma = 94.851(5)degrees Z = 2. Variations in the configurations of the coordinated amines in [CuL1](2+), [CuL2](2+), and [CuL3](2+) have a profound effect on the spectroscopy and electrochemistry of their complexes.

Sensitive detection of nitric oxide using seeded parametric four-wave mixing

A sensitive near-resonant four-wave mixing technique based on two-photon parametric four-wave mixing has been developed. Seeded parametric four-wave mixing requires only a single laser as an additional phase matched seeder field is generated via parametric four-wave mixing of the pump beam in a high gain cell. The seeder field travels collinearly with the pump beam providing efficient nondegenerate four-wave mixing in a second medium. This simple arrangement facilitates the detection of complex molecular spectra by simply scanning the pump laser. Seeded parametric four-wave mixing is demonstrated in both a low pressure cell and an air/acetylene flame with detection of the two-photon C (2) Pi(upsilon'=0)<--X (2) Pi(upsilon =0) spectrum of nitric oxide. From the cell data a detection limit of 10(12) molecules/cm(3) is established. A theoretical model of seeded parametric four-wave mixing is developed from existing parametric four-wave mixing theory. The addition of the seeder field significantly modifies the parametric four-wave mixing behaviour such that in the small signal regime, the signal intensity can readily be made to scale as the cube of the laser pump power while the density dependence follows a more familiar square law dependence, In general, we find excellent agreement between theory and experiment. Limitations to the process result from an ac Stark shift of the two-photon resonance in the high pressure seeder cell caused by the generation of a strong seeder field, as well as a reduction in phase matching efficiency due to the presence of certain buffer species. Various optimizations are suggested which should overcome these limitations, providing even greater detection sensitivity. (C) 1998 American Institute of Physics, [S0021-9606(98)01014-9].