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21.
J. Sanmartín M. R. Bermejo J. A. García-Vázquez J. Romero A. Sousa J. Strähle A. Brodbeck 《Transition Metal Chemistry》1993,18(2):187-190
Summary The electrochemical oxidation of anodic metal (nickel or cobalt) in MeCN solutions of 1-hydroxy-2-pyridinethione (HPT) gives [Ni(PT)2], [Co(PT)2] or [Co(PT)3]. When 1,10-phenanthroline (phen) or 2,2-bipyridine (bipy) are added to the electrolytic phase the product is a complex, [Ni(PT)2L] or [Co(PT)2L] (L = bipy or phen). The i.r., u.v. and 1H- and 13C-n.m.r. spectra of the complexes are discussed.This paper was presented at the 5th Inorganic Chemistry Meeting of the Royal Spanish Chemical Society, Tossa de Mar, Girona, Spain, September 1991. 相似文献
22.
Sousa Pedrares A Teng W Ruhlandt-Senge K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(9):2019-2024
Novel magnesium pyridine-2-thiolates were prepared by using alkane elimination chemistry. The resulting complexes display a metal coordination environment composed of sulfur/nitrogen bonding from the intramolecularly stabilized mercaptopyridine ligand, in addition to coordination by the oxygen centers from two THF donors. The compounds are well-suited model compounds for the magnesium centers in Photosystem I, in which magnesium, situated in the central chlorophyll ligand, is bound to sulfur from a nearby methionine residue. All compounds were characterized by (1)H, (13)C NMR, and IR spectroscopy, in addition to Xray crystallography. 相似文献
23.
de Magalhães Padilha P Rocha JC Moreira JC de Sousa Campos JT do Carmo Federici C 《Talanta》1997,45(2):317-323
Cellulose phosphate (CELLPHOS) was studied as a collector for analytical preconcentration of traces of Cd(II), Cr(III), Cu(II) and Ni(II) from aqueous sample solution. It has been proved that using chromatographic columns packed with CELLPHOS for preconcentration and 1.0 mol 1(-1) HCl for elution the adsorbed analytes are quantitatively enriched. An enrichment factor of 20 (100 ml sample, 5 ml concentrate) was achieved by this separation procedure, which was applied to a series of water analyses (river, sea, bog water). 相似文献
24.
J. Sanmartín M. R. Bermejo J. A. García-Vázquez J. Romero A. Sousa 《Transition Metal Chemistry》1993,18(5):528-530
Summary The electrochemical oxidation of anodic metals (iron and copper) in MeCN solutions of 2-pyridinone (HOPy), 1-hydroxy-2-pyridinethione (HPT), 2-pyridinemethanethiol-1-oxide (HPMTO) or its dimer 2,2-dithiodimethyldipyridine-1,1-dioxide (PMTO)2, gave the simple complexes Fe(OPy)2 · H2O, Cu(OPy)2 · 3H2O, Fe(PT)2 · 3H2O, Fe(PT)3, Cu(PT)2, Fe(PMTO)2·3H2O and Cu(PMTO)2·H2O, respectively. When 1,10-phenanthroline (phen) was added to the electrolytic phase, only two mixed complexes were obtained: Cu(OPy)2phen·3H2O and Fe(PT)2phen·2H2O. The possible molecular structures of the complexes were studied on the basis of their i.r. spectra and magnetic properties. 相似文献
25.
Rodrigues JA Abramovitch RA de Sousa JD Leiva GC 《The Journal of organic chemistry》2004,69(9):2920-2928
In preliminary communications, we reported the diastereoselective synthesis of cularine and sarcocapnine via the intramolecular ring closure of nitrenium and oxenium ions, a new highly diastereoselective reductive methylation with (+)-8-phenylmenthyl chloroacetate followed by reduction with sodium borohydride, and a facile entry to the isoquinoline precursors by aza-Wittig electrocyclic ring closure. We now report the full details of the syntheses of (+)-O-demethylcularine, (+)-cularine, (+)-sarcocapnidine, (+)-sarcocapnine, and (+)-crassifoline and describe different methods of synthesis of their precursors. 相似文献
26.
The ab initio two-state model for electron transfer induced by an external electric field has been applied to the chloride oxidation on Cu, Rh, Pd, Ag, Pt and Au (001) surface models. The two electronic states involved in the model represent physical situations where the electron transferred from the chloride anion to the metal surface lies either on the halide or on the metal substrate. The model assumes that electron transfer takes place when these two states become degenerate and this is achieved by applying an external electric field. Two different situations representing either ultrahigh vacuum or electrochemical conditions have been considered. For the former the present study shows that electric field necessary to achieve degeneracy of the two electronic states is directly related to the metal surface work function whereas for the latter, it is found to be rather insensitive to the metal surface. 相似文献
27.
Mrcia Sousa Bispo Maria das Graas Andrade Korn Elane Santos da Boa Morte Leonardo Sena Gomes Teixeira 《Spectrochimica Acta Part B: Atomic Spectroscopy》2002,57(12):2175-2180
An analytical method for separation and pre-concentration of lead in seawater for determination by inductively coupled plasma optical emission spectrometry has been investigated. Lead was retained in the solid phase (0.5 g) composed of co-precipitated naphthalene and alizarin red. The solid phase quantitatively sorbs Pb(II) at pH 8–9, and the metal was eluted using 5.0 ml of 2 mol l−1 nitric acid. The effect of NaCl, KCl, BaCl2, CaCl2, Na2SO4, MgCl2 and Na3PO4 on the sorption of Pb(II) in the solid phase was studied. A set of solutions containing varying amounts of electrolytes (0.5; 1.0; 3.0 and 5.0% m/v) with Pb (50 μg) was prepared and the recommended procedure applied. The Na3PO4 was found to interfere; the other electrolytes did not interfere up to 5% m/v. A pre-concentration factor of 40 was obtained in this analytical procedure. The limit of detection and limit of quantification for Pb(II) were 53 and 176 μg l−1, respectively. Lead was determined in seawater samples collected in Salvador city, Bahia, Brazil. The precision, expressed as R.S.D., was 1.8–4.6%, and the recovery of lead added to seawater samples was 95–97%. 相似文献
28.
A rapid method is described for the determination of calcium and magnesium in sea. water. The classical gravimetric methods are very lengthy and are susceptible to errors if used for sea-water. The two alkaline earths are determined by complexometric titration using complexen III (disodium ethylenediaminetetra-acetate) as reagent and two indicators (murexide and ériochrome black T) for the determination of calcium and for the sum of Ca+2 and Mg+2 ions. The quantity of magnesium is obtained by difference. While the classical gravimetric methods take at least 24 hours, these two determinations can be effected in 1 hour, giving satisfactory accuracy. 相似文献
29.
Luiza N.H. Arakaki Maria G. da Fonseca Edson C. da Silva Filho Ana Paula de M. Alves Kaline S. de Sousa Andr Leonardo P. Silva 《Thermochimica Acta》2006,450(1-2):12-15
The reaction of ethylene sulfide with 3-aminopropyltrimethoxysilane gave a new silylating agent, which was anchored onto a silica surface via the sol–gel procedure. This surface displayed a chelating moiety containing nitrogen and two sulfur basic centers potentially capable of extracting cations from aqueous solutions. The process of metal extraction was followed by a batch method, and fitted to a modified Langmuir equation. The maximum adsorption capacities found were: 2.06 ± 0.01, 3.72 ± 0.02, and 5.14 ± 0.02 mmol g−1 for Pb(II), Cd(II), and Hg(II), respectively. The enthalpies of bending are: −1.16 ± 0.04, −3.60 ± 0.10, and −8.94 ± 0.03 kJ mol−1 for Cd(II), Pb(II), and Hg(II), respectively. The Gibbs free energies of binding agree with the spontaneity of the proposed reactions between cations and basic centers. 相似文献
30.
The electrochemical oxidation of anodic cobalt, nickel, and zinc in acetonitrile containing both 2-pyrrole-[N-(o-hydroxyphenyl)methylimines] (H2L) and a bidentate ligand (1, 10-phenanthroline(phen) or 2,2′-bipyridine(bipy)) yielded compounds of general formula M(HL)2 · phen and M(HL)2 · bipy (M = Co, Ni, Zn). The crystal structure of 2,2′-bipyridine bis{2-[(2-pyrrole)methylimino]5-methylphenolato}nickel(II) was determined by X-ray diffraction. This compound crystallizes in the orthorhombic space group Pccn with a = 19.430(2), b = 28.488(2), c = 17.567(1) Å. The nickel atom has a distorted octahedral geometry, and the pyrrole nitrogen is not coordinated. The IR, 1H-NMR and UV-visible spectra of the complexes are discussed and related to the structure. 相似文献