Separation and preconcentration of metal ions and their estimation in vitamin, steel and milk samples using o-vanillin-immobilized silica gel

o-Vanillin-immobilized silica gel has been used for the adsorption and estimation of copper, cobalt, iron and zinc by both batch and column techniques. Metal ions were quantitatively retained on the column packed with immobilized silica gel in the pH range 4.0-6.0 for Cu, 5.0-6.0 for Co, 4.5-6.0 for Fe and 6.0-8.0 for Zn. The distribution coefficient D determined for each metal was as follows (ml g(-1)): Fe, 5.4x10(2); Cu, 4.9x10(2); Zn, 4.4x10(2); Co, 3.8x10(2). Methods have been developed to estimate zinc, copper and cobalt in milk, steel and vitamin samples, respectively.     

Solid-phase extraction of metal ions and their estimation in vitamins, steel and milk using 3-hydroxy-2-methyl-1,4-naphthoquinone-immobilized silica gel

3-Hydroxy-2-methyl-1,4-naphthoquinone-immobilized silica gel has been used for the adsorption and estimation of copper, cobalt, iron and zinc by both batch and column techniques. The distribution coefficient D determined for each metal ion was as follows (ml g¹): Fe, 3.6 × 10²; Cu, 3.9 × 10²; Co, 3.8 × 10²; Zn, 4.1 × 10². Methods have been developed to estimate zinc, copper and cobalt in milk, steel and vitamin samples respectively.     

Thermal and structural studies of the chloro complexes of cobalt,nickel and copper with 3-phenylpyridine

The chloro complexes of cobalt, nickel and copper with 3-phenylpyridine were prepared in ethanolic solution from which solid compounds were isolated. The cobalt and copper complexes have stoichiometry M₂LCl₄ while the nickel complex has stoichiometry NiLCl₂. The suggested structure for the cobalt and copper complexes is tetrahedral, while for the nickel complex it is octahedral. Thermal analysis studies show that the cobalt and copper complexes form intermediate complexes before their metal oxides are produced. The nickel complex also forms an intermediate complex and then nickel chloride before the nickel oxide is obtained.     

Chemisorption and thermodynamic data of the interaction between a chelate free acidic center with basic groups attached to grafted silicas

The molecule 2-aminoethanethiol was added to the grafted silylant agent [(3-chlorosilylpropyl)trimethoxysilane] (cpts) onto silica gel(triple bond SilCl), obtaining a surface (triple bond SilSNH(2)) and giving 0.70 mmol g(-1) of nitrogen; the surface of silica was modified with [(3-mercaptosilylpropyl)trimethoxysilane] (mpts) with surface (triple bond SilSH), giving 0.78 mmol g(-1) of sulphur. Both matrices, (triple bond SilSNH(2)) and (triple bond SilSH), adsorb copper and cobalt acetylacetonates from ethanolic solution. Adsorption, using a batchwise process, showed that copper chelate was the most adsorbed. The interactions between the basic centers attached to organic chains of these modified silicas with the cations in the chelates Me(acac)(2) [M=Cu and Co] were followed through calorimetric titrations. Exothermic enthalpic results were obtained for the triple bond SilSNH(2) matrix. The spontaneity of these systems was reflected in negative free Gibbs energy and positive from entropic values.     

Investigations of Cobalt, Nickel, and Copper Diethyldithiocarbamates Using Thermal Lens Spectrometry

Thermal lens spectrometry was used to study the dissociation kinetics of diethyldithiocarbamate complexes of copper(II), cobalt(III), and nickel(II) as a function of pH in the presence of chloride and sulfate ions. It is shown that, as distinct from conventional spectrophotometric and potentiometric measurements, the reversible dissociation of the test complexes and the irreversible oxidation of the ligand can be studied separately (at a level of n × 10^–8–n × 10^–6 M) using thermal lens spectrometry. Because of work in more dilute solutions and due account of the kinetic features of the systems in question, thermal lens spectrometry provides a higher accuracy of the determination of stability constants for diethyldithiocarbamate complexes of copper(II), cobalt(III), and nickel(II). The adsorption of the diethyldithiocarbamate complexes in question from water–ethanol solutions (1 : 3) on Silasorb C₁₈ silica is studied, and the adsorption constants are determined. The limits of detection of copper(II), cobalt(III), and nickel(II) diethyldithiocarbamates obtained in extraction–thermal-lens determination are n × 10^–8 M.     

Silica gel with adsorbed Adogen 464 as an analytical sampling tool for anions

A solid extractant made with the liquid anion-exchanger Adogen 464 supported on silica gel has been prepared and its potential as a resin-like exchange material has been evaluated. In acid media it furnishes a ready available, inexpensive tool for recovery of anionic metal complexes as well as simple anions and for elimination of complex matrices. Copper and cobalt have been recovered (with a concentration factor of 20) from sea-water, natural water, metal alloys and industrial electroplating baths and measured by atomic-absorption spectrophotometry. The detection limits for copper and cobalt are 0.2 and 0.4 ng ml respectively and interferences are minimal. Chromium(VI) has been separated from chromium(III), and a concentration factor of 40 and a detection limit of 0.2 ng ml have been achieved.     

Photoacoustic studies of complexation of copper(II) with an ethylenediamine analog immobilized on silica gel

Photoacoustic spectroscopy and solid-solution distribution measurements are used to study complexation of copper(II) with N-2-aminoethyl-3-aminopropyltrimethoxysilane immobilized on silica gel. Nearly consecutive formation of bis and mono complexes occurs on the surface with increasing copper(II) concentration. Evidence for conversion of bis sites to mono sites with increasing copper(II) concentration was not found. Heterogeneous distribution measurements fit well with a model which assumes two independent types of binding sites. An approximately 2.5:1 ratio of mono to bis sites was found.     

Preconcentration of trace metals in natural waters with 2,2′-dipyridyl-4-amino-3-hydrazino-5-mercapto-1,2,4-triazolehydrazone supported on silica gel

The new hydrazone, supported on silica gel, is used to preconcentrate traces of copper, zinc, lead, nickel, cobalt and cadmium from tap, lake and sea water. Conditions for quantitative retention are established. Copper, zinc, lead, cadmium and nickel are quantitatively eluted with 0.1 M EDTA, and cobalt with 2 M perchloric acid. The metals are measured by atomic absorption spectrometry.     

Solid-phase reagent for molecular spectroscopic determination of heavy metal speciation in natural water

A solid-phase reagent based on 1-(4-adamantyl-2-thiasolylazo)-2-naphthol adsorbed onto silica gel was prepared for Co(II) recovery and preconcentration prior to its sorption-spectroscopic detection. The immobilized reagent was applied to the determination of free cobalt ions in natural water. The solid-phase reagent and chemiluminescent method coupled with membrane filtration, gel-permeation and ion-exchange chromatography were applied to the study of the speciation of iron and cobalt in water from the Dnieper reservoirs and lakes of Kyiv City; their predominant forms were complexes of Fe(III) and Co(II) with dissolved organic matter and fulvic acids play a main role in their complexation.     

Metal ion capillary zone electrophoresis with direct UV detection: Separation of metal cyanide complexes

Mixtures of cyanide complexes of iron(III), copper(I), iron(II), nickel(II), chromium(III), mercury(II), palladium(II), silver(I), cadmium(II), zinc(II), cobalt(II), and cobalt(III) have been separated by capillary zone electrophoresis using a fused silica capillary and 20 mM phosphate buffers containing 1–2 mM sodium cyanide. The complexes were detected by direct UV absorpticn at 214 nm; detection limits are in the mid ppb range for all metals except cadmium and zinc. The different detectability of various metal cyanide complexes enables the application of the method to the analysis of complex matrices such as cyanide plating bath solutions.     

Thermal study of chelates of Co(II), Cu(II), Ni(II), Cr(III), Mo(III), and Fe(III) with bis(acetylacetone)ethylenediimine on activated silica gel surface

The divalent copper, nickel, cobalt and trivalent chromium, molybdenium and iron chelate compounds derived from bis(acetylacetone) ethylenediimine were grafted on activated silica gel using a batch process in methanolic solution. The sequence of the maximum retention capacity was Cr(III)>Mo(III)>Fe(III)>Co(II)>Ni(II)>Cu(II). Calorimetric titration was employed to study the interaction of activated silica gel with these series of metal chelate compounds. Exothermic enthalpic results were obtained throughout all interactions process. The spontaneity of these systems was reflected in negative and positive free Gibbs energy from entropic values.     

Novel routes to Cu(salicylaldimine) covalently bound to silica: combined pulse EPR and in situ attenuated total reflection-IR studies of the immobilization

Several novel routes for the immobilization of modified Cu(salicylaldimine) complexes on commercially available silica are described. New pulse electron paramagnetic resonance (EPR) and electron-nuclear double resonance sequences, which provide more detailed information than that available previously, in combination with continuous wave EPR, allow a definitive assignment of the geometry at the copper center in the immobilized Cu(salicylaldimine). Immobilization of the modified Cu(salicylaldimine) on silica was followed in situ by monitoring the intensity of the characteristic free- and metal-coordinated imine bands as a function of time using attenuated total reflectance IR spectroscopy. On the basis of these studies, the outcome of the Schiff base condensation of Cu-bis(salicylaldehyde) with gamma-aminopropyl-modified silica gel is shown to provide immobilized trans-O(2)N(2)- and O(3)N-coordinated immobilized Cu(salicylaldimine)-type compounds. In addition, trans-O(2)N(2)- or O(3)N-coordinated copper centers are selectively prepared on silica by controlling the aminopropyl modifier loading, thus opening a route to compounds not available by conventional synthesis. The O(3)N-coordinated Cu(salicylaldimine)-type compound on silica was investigated as a precursor for the synthesis of a tethered chiral Cu(salicylaldimine) via reaction of the coordinated carbonyl group with (R)-(+)-alpha-methylbenzylamine. Supported Cu(salicylaldimine) was also prepared via the immobilization of the appropriate silylethoxy-modified homogeneous precursor on silica gel. Precursors and silica-supported Cu(salicylaldimine) materials have been fully characterized. Comparisons are drawn with related Cu(salicylaldimine) immobilized in silica aerogels.     

Sorption of iron(II) and ruthenium(III)-triazine complexes on silica gel and its analytical applicability

2,4,6-Tri(2′-pyridyl)-s-triazine (TPTZ) complexes with iron(II) and ruthenium(III) were prepared. Their sorption and desorption features on silica gel have been investigated. Both complexes were strongly adsorbed. This has been utilized for separating and preconcentrating iron(II) and ruthenium(III) using TPTZ-impregnated silica gel. The chromatographic behavior of TPTZ on silica gel column was examined and found to be effective modifier for silica gel surface. The sorption capacity of silica gel for those metal-triazine complexes has been determined under static conditions and was found to be 5.28 × 10^–3 mM (Fe(TPTZ)₂²⁺) and 2.9 × 10^–3 mM (Ru(TPTZ)₂³⁺). Saturated methanolic solutions of KI or 25% NaClO₄ solutions desorbed both complexes quantitatively from the silica gel surface.     

Cobalt-extraction studies on dithiocarbamate grafted on silica gel surface

Extraction of cobalt(II) ion from aqueous solution was studied using silica gel grafted with dithiocarbamate ligand (Si–dtc), which was prepared by reacting silica gel with γ-aminopropyltriethoxysilane followed by alkaline carbon disulfide. ²⁹Si MAS NMR, IR spectra were taken to establish the grafting of dithiocarbamate ligand on silica gel. This modified surface contains 0.37 mmol g⁻¹ of the ligand sites available for the extraction of cobalt. The sorbent extracts cobalt only when the pH of the aqueous phase is above 7 and the extraction process does not follow ideal ion-exchange mechanism. The electronic absorption spectra of cobalt present in the sorbent phase suggested the oxidation of Co(II) to Co(III). Kinetic data were fitted to surface complexation model and the rate constant (k_s) for such model was found to vary from 1.5×10⁻³ to 5.82×10⁻³ l mg⁻¹ min⁻¹ depending on the initial concentration of cobalt. An estimate of enthalpy and entropy changes accompanying the extraction was obtained by temperature variation method. The increase in the overall entropy of the system seems to favour the extraction of cobalt by Si–dtc.     

THE SYNTHESES AND PROPERTIES OF COBALT(II), NICKEL(II) AND COPPER(II) COMPLEXES WITH SOME 1,4-BENZODIAZEPINES

Abstract

The preparation and characterization of some cobalt(II), nickel(II) and copper(II) complexes with 7-chloro-2-methylamino-5-phenyl-3H-1, 4-benzodiazepin-4-oxide and 1, 3-dihydro-7-nitro-5-phenyl-2H-1, 4-benzodiazepin-2-one are reported. The complexes have been studied by means of magnetic susceptibility measurements, infrared and far infrared spectra, electronic spectra and conductivity measurements. Assignments for the metal-ligand and metal-halide bands have also been made. The evidence suggests that the cobalt(II) and nickel(II) complexes have a pseudotetrahedral symmetry, whereas the copper(II) complexes are octahedral.     

Preparation of ion-imprinted silica gels functionalized with glycine, diglycine, and triglycine and their adsorption properties for copper ions

We report a new procedure for modifying the surface of silica gels with glycine, diglycine, and triglycine in the presence of copper ions to create a new type of copper-imprinted sorbent, which exhibits a high adsorption capacity and selectivity for copper ions. Our results show that copper adsorbed onto the copper-imprinted silica gel is 50% higher than that on nonimprinted silica gel at pH 4.5. The high adsorption capacity observed for the copper-imprinted silica gel is attributed to the stable copper complexes formed with two adjacent glycine, diglycine, or triglycine molecules with proper intermolecular distances obtained from the ion-imprinting procedure. Another possible reason for the high adsorption capacity is that the ion-imprinting procedure prevents the surface from being overcrowded; therefore, copper ions can form very stable 1:1 complexes with immobilized diglycine or triglycine. Interestingly, the imprinting effect is even more pronounced when the adsorption experiments are conducted in the presence of competing metal ions such as magnesium and calcium. The copper-imprinted silica gel exhibits a higher adsorption capacity than does the nonimprinted silica gel for all pH values, even when the concentrations of magnesium and calcium are 50 and 76 times higher than the concentration of copper.     

Cytotoxicity of cobalt complexes of furan oximes in murine and human tissue‐cultured cell lines

The copper complexes of 2‐furaldehyde and furan oximes have previously demonstrated potent cytotoxicity, L1210 DNA synthesis inhibition, DNA topoisomerase II inhibition and DNA fragmentation. Currently a series of cobalt metal complexes of 2‐furaldehyde oximes were compared with copper complexes of furan oximes to determine whether the type of metal is important to the cytotoxicity and mode of action of the complexes. The cobalt complexes of furan oximes, like the copper complexes, were shown to be cytotoxic to suspended tumor cell lines, e.g. leukemias, lymphomas, acute monocytic leukemia and HeLa‐S³ uterine carcinoma. The cobalt complexes did not demonstrate dramatic cytotoxicity against the growth of tumors derived from solid human tumor lines. The cobalt complexes preferentially inhibited L1210 DNA synthesis, followed by inhibition of RNA and protein synthesis from 25 to 100 µM over 60 min. These agents, like the copper complexes of 2‐furaldehyde and furan oximes, were inhibitors of DNA polymerase α activity and de novo purine synthesis with marginal inhibition of ribonucleoside reductase and dihydrofolate reductase activities with DNA fragmentation. Unlike the copper complexes, the cobalt complexes did not inhibit L1210 DNA topoisomerase II activity but did reduce thymidylate synthetase activity. Thus, varying the type of metal within the complexes of 2‐furaldehyde and furan oximes produces differences in both cytotoxicity and mode of action. Copyright © 1999 John Wiley & Sons, Ltd.     

Molecular docking,HOMO-LUMO and quantum chemical computation analysis of anti-glyoximehydrazone derivatives containing pyrazolone moiety and their transition metal complexes

In this study, in order to obtain biologically active compounds, a series of anti-glyoximehydrazone ligands bearing vic-dioxime, hydrazone, and pyrazole moieties and their (O•••H–O) bridged nickel(II), cobalt(II) and copper(II) metal complexes were prepared. Further, the molecular docking studies were carried out on those ligands and their nickel(II), cobalt(II) and copper(II) metal complexes to analyze the interaction with EGFR Kinase domain complexed with tak-285 (PDB ID: 3POZ) and human androgen receptor T877A mutant (PDB ID:2OZ7). In addition, the compounds were optimized by using B3LYP/6-311G+(d,p) level of Density Functional Theory (DFT) to evaluate the HOMO–LUMO contours and quantum chemical parameters. Also, bioactivity analysis were performed.Metal complexes had higher binding affinities against 3POZ and 2OZ7. The most promising compounds for 3POZ were nickel(II) and copper(II) metal complexes. However, for the 2OZ7 target receptor, cobalt(II) and copper(II) metal complexes were the possible hit compounds. Furthermore, cobalt(II) metal complex of ligand two was found to be the most reactive one among others. Moreover, it had the highest ω which is related to a potent higher electrophilic character. It was determined that all the compounds had moderate bioactivity.In conclusion, nickel(II), cobalt(II), and copper(II) complexes could be powerful hit compounds for anti-cancer drug discovery studies.     

Linear relation between RM values obtained in salting-out planar chromatography and mol % ammonium sulphate in aqueous solvent systems

Summary Existence of a linear relation between R_M and mol % ammonium sulphate in an aqueous solvent system, established earlier for mixed aminocarboxylato cobalt(III) complexes in salting-out, thin-layer chromatography on silica gel, polyacrylonitrile and cellulose, was verified by linear regression analysis of the corresponding data reported in the literature for 108 organic compounds separated on cellulose. The same regularity was also found for seven inorganic anions.     

Heterometallic architectures based on the combination of heteroleptic copper and cobalt complexes with silver salts

A strategy for the formation of heterometallic coordination polymers based on novel copper(II) and cobalt(III) heteroleptic complexes (acacCN)Cu(dpm) and (acacCN)Co(dpm)(2) (acacCN = 3-cyanoacetylacetonate; dpm = dipyrrin) is presented. Using dipyrrins appended with a p- or m-pyridyl group, dpm-4py and dpm-3py, four novel copper and cobalt complexes were prepared and characterized both in solution and in the solid state. These two classes of complexes show different electrochemical properties upon investigation by cyclic voltammetry in CH(2)Cl(2). While the copper complexes show only irreversible reduction processes, the voltammogram of the cobalt species reveals the presence of two quasi-reversible reductions. In the solid state, the copper(II) compounds self-assemble to form one-dimensional architectures upon coordination of the peripheral pyridyl group to the copper center, as characterized by single-crystal X-ray diffraction. Owing to the filled coordination sphere of the octahedral cobalt centers, the (acacCN)Co(dpm-py)(2) compounds crystallize as isolated molecules. Upon reaction with silver salts, these complexes form crystalline heterometallic architectures with different organization and dimensionality, depending on the nature of the metal center and the position of the nitrogen atom in the pyridyl group. The two copper complexes lead to the formation of trinuclear species, {[(acacCN)Cu(dpm-py)](2)Ag}(+), resulting from coordination of the pyridyl groups to the silver cations. However, while meta-functionalized complexes self-assemble into an extended architecture via weak interaction of the peripheral nitrile of the acacCN ligand to the Ag(+) cation, this interaction is not present in the para-functionalized analogue. In both networks based on the Ag(BF(4)) salt, coordination of the tetrafluoroborate anion to the silver center in the rather rare chelate mode is observed. Upon assembly of the cobalt metallatectons with silver salts, two-dimensional (2D) coordination polymers are obtained in crystalline form, resulting, however, from different sets of interactions. Indeed, no coordination of the peripheral nitrile of the acacCN ligand is observed in the network incorporating the m-pyridyl-appended dpm; coordination of the pyridyl groups to the silver center and d(10)-d(10) interactions lead to a 2D architecture. In the case of the para analogue, a 2D honeycomb network is observed owing to coordination of the Ag(I) ion to two pyridyl nitrogen atoms and to one peripheral nitrile group of a acacCN ligand. This latter polymer represents a geometrical hybrid of the networks reported in the literature based on homoleptic Co(dpm-4py)(3) and Cr(acacCN)(3) complexes.