Search results for "COPP"
showing 10 items of 3147 documents
Discriminating octahedral transition metal ions: highly selective tripodal tris-(2,2′-bipyridine) functionalized piperazine cyclophane receptor for C…
2011
New tripodal transition metal ion receptors, tris(5-ethoxycarbonyl-2,2'-bipyridine) and tris(5-carboxylate-2,2'-bipyridine) substituted 27-membered trimeric piperazine cyclophanes 5 and 7 as well as tetra(5-ethoxycarbonyl-2,2'-bipyridine) substituted 36-membered tetrameric piperazine cyclophane 6, have been prepared and their transition metal ion complexing properties studied in solution by UV-vis spectroscopy and in the solid state by single-crystal X-ray diffraction. The crystal structures of [H(3)5(3+)·Fe(2+)]·4(ClO(4)(-))·CF(3)COO(-) (V), [H(3)7(2+)·Fe(2+)]·2(SO(4)(2-)) (VII) and the reference complex [tris(5,5'-bis(ethoxycarbonyl)-2,2'-bipyridine)Fe(II) perchlorate] (I) showed that the…
Serum metal levels in a population of Spanish pregnant women
2022
Objective: To describe serum levels of calcium, copper, selenium, magnesium, iron and zinc and evaluate their relationship with maternal socio-demographic characteristics and dietary variables in women in the first trimester of pregnancy. Method: Cross-sectional study with 1279 participants from the INMA cohorts. Results: The concentrations of the elements analyzed were within the normal range. Associations with higher levels of these metals were found for calcium with white meat intake (p = 0.026), for cop-per with excess body weight (p 71 g/day) (p = 0.014) and having been born in Spain (p = 0.001). Further, lower iron levels were associated with being overweight (p = 0.021) or obese (p <…
Hydrophobic effects in the stabilisation of copper(I) by the macrocyclic ligands 16,17,19,20-tetramethyl-2,6,9,13-tetraaza[14]paracyclophane and 14,1…
1996
Abstract The interaction of Cu 2+ with the para -azacychlophanes 16,17,19,20-tetramethyl-2,6,9,13-tetraazal[14]paracyclophane (L1) and 14,15,17,18-tetramethyl-2,5,8,11-tetraaza[12]paracyclophane (L2) has been studied by potentiometry, and direct microcalorimetry at 298.1±0.1 K in 0.15 mol dm −3 NaClO 4 . The stability constants (log K CuLi = 13.35(3), log K CuL2 = 9.32(4)) and the thermodynamic parameters ( ΔH ° CuL1 = −47.3(8) kJ mol −1 , ΔH ° CuL2 = 20.9(8) kJ mol −1 ) evidence that not all four nitrogen atoms in the ligands are involved in the coordination to the metal centre. These results, particulary in the case of L1, are similar to those reported for the analogous cyclophanes contai…
Enantioselective addition of nitromethane to α-keto esters catalyzed by copper(ii)–iminopyridine complexes
2008
The copper complex of a chiral iminopyridine easily prepared from (R)-(-)-fenchone and picolylamine catalyzes the enantioselective Henry (nitroaldol) reaction between nitromethane and alpha-keto esters. Good yields and modest to good enantioselectivities are obtained for a wide range of alpha-keto esters, bearing aromatic, alkyl or alkenyl groups attached to the ketone carbonyl group.
Analysis of socio-economic impact of Konkola Copper Mine (KCM) on the mining community in Zambia : a case study of Chingola Town
2008
This thesis focuses on the impact of Konkola Copper Mine (KCM). This company is a Multinational Mining Corporation. It is based in Chingola town in Zambia. The study seeks to establish whether the Mining company is contributing to the development of the town or not. It also examines the development agreements which the company entered into with government and show how this commitment has affected the company’s contributions to the local community. Specifically, the study seeks to critically examine the development agreements with a view to establishing whether these agreements emphasized strict observance of corporate social responsibilities or not The methodological approach used in this s…
Enantioselective Henry addition of methyl 4-nitrobutyrate to aldehydes. Chiral building blocks for 2-pyrrolidinones and other derivatives.
2010
A catalytic highly enantioselective Henry addition of methyl 4-nitrobutyrate to aldehydes using a Cu(II)-amino pyridine complex as catalyst is described. The products resulting from this reaction constitute a new, highly versatile family of chiral building blocks as a result of the presence of three different functional groups on the molecule. These products have been transformed into nonracemic chiral gamma-lactams, 5-hydroxy-5-substituted levulinic acid derivatives, and delta-lactones.
Towards sensory Langmuir monolayers consisting of macrocyclic pentaaminoanthraquinone
2014
A pentaazamacrocycle incorporating an intracyclic anthraquinone fragment (PENTAQ) was synthesized with the aim of forming metal-responsive Langmuir monolayers. PENTAQ allows a good discrimination by naked eye of copper ions in methanol–water solutions (50 : 50 v/v). Spectrophotometric investigations of the protonation and Cu2+ binding properties of PENTAQ were undertaken in order to gain a deeper insight into the pH-dependent speciation as well as the color changing process. PENTAQ monolayers at air/water and air/methanol–water interfaces were prepared according to the Langmuir procedure. The structure of the monolayers can be tuned by varying the pH of the aqueous subphase, since it was fo…
Sorption of copper(II) ions in the biomass of alga Spirogyra sp.
2012
Abstract Sorption of copper ions by the alga Spirogyra sp. was investigated to determine the influence of experimental conditions and the methods of sample preparation on the process. The experiments were carried out both under the static and the dynamic conditions. Kinetics and equilibrium parameters of the sorption were evaluated. In addition, the influence was studied of the algae preparation methods on the conductivity of demineralized water in which the algae samples were immersed. The static experiments showed that the sorption of Cu2+ ions reached equilibrium in about 30 min, with approximately 90% of the ions adsorbed in the initial 15 min. The sorption capacity determined from the …
Effect of EDTA on divalent metal adsorption onto grape stalk and exhausted coffee wastes
2007
In the present work, two industrial vegetable wastes, grape stalk, coming from a wine producer, and exhausted coffee, coming from a soluble coffee manufacturer, have been investigated for the removal of Cu(II) and Ni(II) from aqueous solutions in presence and in absence of the strongly complexing agent EDTA. Effects of pH and metal-EDTA molar ratio, kinetics as a function of sorbent concentration, and sorption equilibrium for both metals onto both sorbents were evaluated in batch experiments. Metal uptake was dependent of pH, reaching a maximum from pH around 5.5. EDTA was found to dramatically reduce metal adsorption, reaching total uptake inhibition for both metals onto both sorbents at e…
Development of iron oxide/activated carbon nanoparticle composite for the removal of Cr(VI), Cu(II) and Cd(II) ions from aqueous solution
2018
Iron oxide (Fe3O4) and iron oxide/activated carbon (Fe3O4/AC) were fabricated by co-precipitation method for the removal of Cr(VI), Cu(II) and Cd(II) ions from aqueous solution in batch mode. These nanoparticles were characterized by BET, FTIR, XRD, SEM/TEM and VSM. The optimum conditions for the removal of ions were pH = 2 for Cr(VI) and 6 for Cu(II) and Cd(II), initial metal ion concentration = 50 mg L−1, nanoparticle dose = 50 mg/10 mL, temperature = 25 ± 1 °C, shaking speed = 180 rpm and contact time = 3 h. The equilibrium data of ions sorption were well described by Langmuir, Freundlich, Redlich-Peterson and Intraparticle Diffusion model. The R2 values obtained by Langmuir model were h…