Cobalt Metal Complexes Research Articles

New ceramic based membranes for catalytic membrane reactorsMembranes modified by cobalt complexes with 1,3-diazoles

Modification of the surfaces of inorganic membranes which have the composition 70% Al 2 O 3 +30% ZrO 2 stabilized by Y 2 O 3 has been carried out. This was done by first reacting them with silica and then with γ-aminopropyltriethoxysilane, cyanuric chloride (or diiododecene) and 1,3-diazole (imidazole or histamine). It was found that the modification of membrane materials by disperse silica occurred only in the subsurface layer and this resulted in the microfiltration membrane acquiring ultrafiltration properties. The retentions of the silica-modified membranes with respect to dextrans of different molecular weights differed from those of the unmodified membranes. Heterogenized metal complexes of transition metals with 1,3-diazoles, grafted onto the membrane surfaces, were obtained. It was established that the cobalt metal complexes with 1,3-diazoles had a deformed tetrahedral structure and it was only the nitrogen atoms of the grafted heterocycles of imidazole which were involved in the formation of four-coordinate metal complexes. The catalytic properties of the obtained membrane materials in the model reaction of the liquid-phase oxidation of cumene have been studied and the occurrence of a radical-chain process with the participation of the catalytically active membranes has been established. The formation of radicals takes place due to the oxygenation of heterogenized metal complexes, according to the following reaction: O 2 ·Co(II)→O − 2 ·Co(III). The catalytic reaction of cumene oxidation proceeds with the participation of Co(III) catalysts according to a mechanism involving electron transfer. The synthesized catalytic membrane materials can be used for the processes of oxidation of organic compounds under mild conditions.

Synthesis of novel molecular sieves using a metal complex as a template

The synthesis and characterization of novel molecular sieves containing bis(pentamethylcyclopentadienyl) cobalt(III) ion are described. Several types of molecular sieves were prepared using the cobalt metal complex as a template that was shown to be incorporated as a guest molecule within the molecular sieve. Molecular sieves prepared using bis(pentamethylcyclopentadienyl) cobalt(III) ion as template were characterized as having a pore size at least as large as 7 Å. Other molecular sieves were also prepared using bis(cyclopentadienyl) cobalt(III) templates. The compounds are attractive as catalysts in a wide range of applications.

Poly[4-Amino-2,6-pyrimidinodithiocarbamate] and Its Cobalt, Nickel, and Copper Complexes

The pyrimidinodithiocarbamate polymer was prepared from the reaction of 2-mercapto-4,6-diaminopyrimidine with carbon disulfide, followed by condensation through the removal of H2S gas. Three polymer–metal complexes of cobalt, nickel, and copper were then prepared. The polymer and its complexes were investigated by elemental analyses, UV, IR, and magnetic susceptibility. The DC electrical conductivity variation, with the temperature in the region 298–498 K, of the polymer in its undoped and doped (5% iodine and 5% NiCl2) states and, also, of the three polymer complexes was determined. All the complexes showed an increase in conductivity with an increase in temperature in a semiconductor behavior. The thermal stability of the complexes was studied using the TGA technique. The structures of the polymer and its complexes were assigned. The proposed structure of the complexes is (MLX2.mH2O)n. All the polymer complexes are thermally stable, are insoluble in common organic solvents, and have high melting points.

Analytical Application of Silica Gel Modified with Didecylaminoethyl-β-Tridecylammonium Iodide

Sorption of a high molecular weight quaternary ammonium salt, didecylaminoethyl-β-tridecylammonium iodide (DDATD) on different types of sorbents was investigated. The nature of reagent adsorption on silica gel was examined by spectroscopic and computer methods. The sorption of anionic metal complexes of cobalt, copper, zinc and manganese on silica gel modified with DDATD was studied. The possibility of recovery of cobalt and copper thiocyanate complexes and their further atomic absorption determination is shown. Modified sorbent was applied to cobalt chemiluminescence and determined in natural water and a nickel preparation (detection limit, 2 μg/l.).

The Reaction Behavior of White Phosphorus with Metal Complexes of Cobalt and Molybdenum

Abstract Studies of the reaction pathway of tetrahedral P4 with cobalt- and molybdenum coordination compounds lead to novel complexes containing PX-ligands (x = 2,4) in unusual binding modes.

Metal complexes of cobalt(II), nickel(II), copper(II) and zinc(II) with N-(2-hydroxy-1-naphthylidene)-L-amino acids

A new series of complexes of Co(II), Ni(II), Cu(II) and Zn(II) with imines derived from the condensation of 2-hydroxy-1-naphthaldehyde with L-amino acids (L-alanine and L-isoleucine) have been synthesized. The complexes are characterized by elemental analyses,1HNMR, IR, electronic spectra and conductivity and magnetic susceptibility measurements. Metal ions function as a trap for Schiff base intermediates. Spectroscopic studies reveal that the ligands are dibasic terdentate with the O, N, O donor set.

Structural studies of 3-amino-4-(substituted arylazo)-5-(1H)pyrazolone compounds

Transition metal complexes of cobalt(II), nickel(II), copper(II) and palladium(II) with 3-amino-4-(arylazo)-5-(1H)pyrazolones (Aryl=Ph, 4-C6H4CO2H, 4-C6H4-OMe, 3-C6H4Cl, 3-C6H4CO2H, 3-C6H4NO2, 3-C6H4-Me, 3-C6H4OH and 2-C6H4CO2H) are discussed. The stoichiometry of the complexes is: 1∶1, 2∶3 CoII; 1∶1 NiII; 1∶1, 2∶1 CuII and 1∶2 PdII. The investigations suggest rhombic symmetry with 4- or 5-coordinate CoII, square planar and tetrahedral configuration for NiII, tetrahedral CuII and square planar for PdII complexes. The complexes contain no anions.

Structural Characterization of Several Metal(II) 2-Methyl-8-quinolinolato Complexes in Several Organic Solvents

Abstract Bivalent metal complexes of cobalt(II), nickel(II), copper(II), and zinc(II) with 2-methyl-8-quinolinol (2MeHql) were prepared. Their properties, such as those shown by thermogravimetry (TG) and differential thermal analysis (DTA), X-ray diffraction, magnetic susceptibility, and the optical spectra, were measured and compared with those of 8-quinolinolato complexes. All the metal complexes prepared here are monohydrates, whereas their 8-quinolinolato complexes are dihydrates. The methyl group at the 2-position of the quinoline ring caused a shift of about 40–80 °C in the dehydration temperature, and, as a result of the dehydration, a dimer anhydrate was produced. The dimer-formation conditions were established in chloroform and dioxane solutions. However, the addition of such basic solvents as pyridine, water, and methanol cleaved the bridge linkages in complexes and produced a distorted octahedral configuration by solvent-binding in the axial position. The existence of a copper complex with a dimer structure such as has been shown in other metal complexes was not verified in any of the solvents used here.

2,2,3,4,4-pentamethylphosphetanic acid, C 8H 16PO 2H: salts, complexes and a hydrogen bonded amine adduct

The conjugate base of the title acid, i.e. C 8H 16PO 2 −, has been investigated as its simple salts, as a ligand in transition metal complexes of cobalt and ruthenium, and as a secondary amonium salt in which hydrogen bonding between anion and cation occurs.

Metal complexes of cobalt, nickel, copper and silver with syn-thiophene-2-aldoxime

Metal complexes of cobalt, nickel, copper and silver with syn-thiophene-2-aldoxime

Synthesis and characterization of metal complexes of cobalt(II), nickel(II), copper(II), and silver(I) with syn‐thiophene‐2‐aldoxime

AbstractComplexes of syn‐thiophene‐2‐aldoxime (TDH) have been synthesised and characterized on the basis of elemental analysis, molecular weight, conductance, magnetic susceptibility and i. r. spectra. These are [Co(TDH)4Cl2], [Co(TD)2], [Ni(TDH)4Cl2], [Ni(TD)2(TDH)], [Cu(CH3COO)2(TDH)]2, [Cu(TD)(OH)]2 and AgNO3 · 2TDH.In these complexes the ligand (TDH) functions as monodentate (coordinating through nitrogen atom) or bidentate (coordinating through the nitrogen and sulphur atoms). The CS stretching frequency (of the thiophene ring) at 718 cm−1 may be taken as the criteria for the denticity of this ligand. A shift to lower frequency is observed in the complex if the ligand acts as a bidentate. However, this band is not affected if the ligand acts as monodentate.

3,5-Dimethyl pyrazolato metal complexes of cobalt(II), nickel(II) and copper(I)

3,5-Dimethyl pyrazolato metal complexes of cobalt(II), nickel(II) and copper(I)

Studies on Antibacterial and Antifungal Activities and Minimum Inhibitory Concentrations of Mixed Ligand Transition Metal Complexes of Dibasic Acids as Primary and Heterocyclic Bases as Secondary Ligands

Mixed ligand (diphenic/ adipic as primary Ligand and quinoline / 8 - hydroxyquinoline as secondary) transition metal complexes of Cobalt (II), Cupper (II), Rhodium (III) and Platinum (IV) ions were synthesized and characterized. Their antibacterial activities against ten bacteria had been evaluated by the disc diffusion method,whilst their antifungal activities against two fungi had been also evaluated by the same method. Minimum inhibitory concentrations (MIC) had been evaluated against six bacteria. The MIC of the complexes against Shigella dysenteriae, Samonella typhi, Streptococcus-β-haemolyticus and Bacillus megaterium were 32 μg/ml; whilst Escherichia coli and Samonella typhi-A the MIC of Co (II) and Pt (IV) were 32μg/ml and those of Cu(II) and Rh(III) complexes were 64 μg/ml. It was found that Cobalt (II), Cupper (II) & Rhodium (III) complexes had pronounced antibacterial and antifungal activities. Platinum (IV) complex had moderate antibacterial and antifungal activity. These values indicate that these are active compounds. Key words: Mixed Ligand; Transition metal; Antimicrobial Activity; Antifungal Activity Minimum Inhibitory Concentrations (MIC) DOI: http://dx.doi.org/10.3329/bjsir.v46i3.9044 BJSIR 2011; 46(3): 365-368

Metal Complexing by Tris Buffer

THE inhibitory effect of tris buffer (I)* relative to certain other buffers in a number of biochemical reactions is known1,2. For example, tris gives lower values for the rates of synthesis of proteins in cell-free bacterial preparations than some other buffers. We report here some observations on the inhibition of the reactions of metal complexes of cobalt(III) which may be relevant in assessing the possible inhibitory effects of tris buffer in more complex systems.