Some new chromogens for iron, cobalt, and copper Substituted hydrazidines and 1,2,4-triazines containing the ferroin group

The spectral characteristics and solution conditions requisite for formation of the iron(II), cobalt(II), and copper(I) complexes of some newly synthesised compounds containing the ferroin functional grouping have been determined. These properties are useful for evaluation of the possible analytical effectiveness of the compounds as spectrophotometric reagents for the determination of iron, cobalt, and copper.     

Molten potassium thiocyanate: The reactions of some compounds of iron,cobalt, nickel,copper and zinc

The electronic spectra of four transition metal cations stable in molten potassium thiocyanate [Fe(II), Co(II), Ni(II) and Cu(I)] are reported together with their reactions and those of three unstable cations [Fe(III), Co(III) and Cu(II)] with a variety of anions including cyanide, cyanate and sulphide. A novel reduction of zinc(II) sulphate is also reported.     

Mechanism of carbothermal reduction of iron, cobalt, nickel and copper oxides

A new scheme of thermal dissociation which is based on the dissociative evaporation of the reactant with simultaneous condensation of the low-volatile product has been invoked to interpret the kinetics of reduction of FeO, CoO, NiO and Cu₂O by carbon. A critical analysis of literature data and their comparison with theoretical calculations has shown that the main kinetic characteristics of carbothermal reduction, including the initial decomposition temperature and activation energy are in full agreement with the proposed mechanism of decomposition. Condensation of the low-volatile product (metal vapour) in the reaction zone and partial transport of condensation energy to the oxide account for the features which are typical of solid state reactions and manifest themselves in the appearance of periods of induction and acceleration in the course of the process. Carbon fulfils the role of buffer in this process. This is supported by an appearance of metals in the condensed phase and a higher than equilibrium partial pressure of oxygen in high-vacuum experiments with Knudsen cells.     

Gravimetric determination of cobalt and nickel,and their separations from copper with n-benzoylphenylhydroxylamine

N-Benzoylphenylhydroxylamine can be used for the gravimetric determination of cobalt and nickel. The precipitates can be weighed as such, or ignited and weighed as cobalt sulphate or nickclous oxide. Cobalt or nickel can be separated from copper with the reagent.     

Simultaneous determination of iron, cobalt, nickel and copper by UV-visible spectrophotometry with multivariate calibration

A method for the simultaneous spectrophotometric determination of the divalent ions of iron, cobalt, nickel and copper based on the formation of their complexes with 1,5-bis(di-2-pyridylmethylene) thiocarbonohydrazide (DPTH) is proposed. The resolution of quaternary mixtures of these metallic ions was accomplished by several chemometric approaches. A comparative study of the results obtained for simultaneous determinations in mixture by using principal component regression (PCR) and partial least-squares regression (PLS-1 and PLS-2) for absorbance, first-derivative and second-derivative data is presented. In general, the best recovery values are obtained by the PLS-2 method for absorbance data. This procedure allows the simultaneous determination of the cited ions in alloys and biological materials Good reliability of the determination was proved.     

The determination of aluminum,nickel, cobalt,copper, and iron in alnico

A method has been developed for the determination of the major constituents of Alnico based on an anion exchange separation of the chloride complexes and the subsequent determination of aluminum, nickel, copper, cobalt and iron with EDTA. The method is more convenient than conventional classical methods.     

Spectrophotometric determination of copper, nickel, cobalt, iron and manganese as their pyridine thiocyanates Simultaneous determination in mixtures

Spectrophotometric determinations of copper, nickel, cobalt, iron, and manganese, based on the chloroform extraction of the metal pyridine thiocyanates, have been investigated. Optimum conditions require the pH of the aqueous solution to be in the range about 5–8; tartaric acid is used to prevent precipitation of hydrous oxides. An excess of pyridine must be used because chloroform readily extracts pyridine from the aqueous solution. Results are improved by making the extraction from a solution of high ionic strength (2 or above), which is provided by magnesium nitrate. Perchlorate decreases the absorbance, but the effect is essentially constant over a perchlorate concentration range of 0.8 to 2M. Although the metal pyridine thiocyanates are extracted by benzene, substituted benzenes, and halogenated hydrocarbons, chloroform is superior to other solvents in extraction efficiency and in colour stability of the extracted species. An example is given of the simultaneous determination of copper, nickel, cobalt, and iron in the same solution. Anions that also form metal pyridine compounds must be absent.     

含Fe、Co、Ni的LDHs为催化剂前体生长碳纳米管

分别以具有相似Fe、Co、Ni含量的层状双金属氢氧化物（LDHs）为催化剂前体,用化学气相沉积的方法生长碳纳米管（CNTs）。 催化剂由LDHs焙烧还原得到。 通过X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）及拉曼光谱（Raman）测试技术对LDHs及其焙烧产物的结构、CNTs的形貌和结构进行了研究。 结果表明,3种催化剂生长的CNTs均为多壁结构;其中Co催化剂活性较低,生长CNTs的管径较细、石墨化程度较高;Ni催化剂的活性较高,生长CNTs的密度较大、管壁较厚、石墨化程度较差;Fe催化剂的活性介于Co和Ni之间。 催化剂活性及CNTs的密度可以由生长CNTs的结构来解释。     

Colorimetric determination of copper, nickel and cobalt in their respective soaps

Summary The metal ion content of heavy metal soaps can be successfully determined colorimetrically using their dilute solutions in pyridine. Measurements with copper and nickel soaps (myristates and palmitates) could be carried out at 675 and 650 nm respectively, those for the corresponding cobalt soaps (myristate and palmitate) at 550 nm.

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Zusammenfassung Der Metallgehalt von Schwermetallseifen kann mit gutem Erfolg colorimetrisch bestimmt werden, wenn man die verdünnte Lösung der Substanz in Pyridin verwendet. Messungen an Kupfer- und Nickelseifen (Myristate und Palmitate) wurden bei 675 bzw. 650 nm, an Kobaltseifen (ebenfalls Myristat und Palmitat) bei 550 nm durchgeführt.

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Thanks are due to Prof. A. R. Kidwai for providing facilities and to the Council of Scientific and Industrial Research, India for the award of a fellowship to one of us (R. H.) to carry out this work.     

Paramagnetic shifts in complexes of N-vinylimidazole with manganese,iron, cobalt,nickel, and copper chlorides

The observed paramagnetic shifts and broadenings of the resonance lines in the PMR spectrum of N-vinylimidazole upon the addition of its complexes with manganese, iron, cobalt, nickel, and copper chlorides are compared.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 994–995, July, 1972.We thank Doctor of Chemical Sciences Yu. N. Molin for his assistance in carrying out this investigation.     

Boron rings containing planar octa-and enneacoordinate cobalt,iron and nickel metal elements

For a series of boron rings with planar hyper-coordinate 8th group transition metal atoms, singlet 1FeB8-2, multiplet kFeB9n (n = -1, k = 1; n = 0, k = 2), singlet 1CoB8n(n = -1, 1, 3), multiplet kCoB9n (n = 1, k = 2; n = 0, k = 1) and singlet 1NiB9 , the geometry structures have been optimized to be local minima on corresponding potential hyper-surfaces. The electron structures are discussed by orbital analysis and the aromaticity is predicted by nucleus-independent chemical shifts calculation at both the B3LYP/6-311 G* and BP86/6-311 G* levels of theory, respectively. The results suggest that all these structures with high symmetry planar geometries are stable and have aromatic properties with six π valence electrons.     

Metal-alane adducts with zero-valent nickel, cobalt, and iron

Coordination complexes that pair a zero-valent transition metal (Ni, Co, Fe) and an aluminum(III) center have been prepared. They add to the few examples of structurally characterized metal alanes and are the first reported metallalumatranes. To understand the M-Al interaction and gauge the effect of varying the late metal, the complexes were characterized by X-ray crystallography, electrochemistry, UV-Vis-NIR and NMR spectroscopies, and theoretical calculations. The M-Al bond strength decreases with varying M in the order Ni > Co > Fe.     

Synthesis and crystal structures of some cobalt halide derivatives containing alkyl or silanolato groups

The alkylcobalt halide (2) and the lithium silanolatocobaltates Li(THF)₂(μ-Br)₂Co(μ-OSiMe₃)₂Co(μ-Br)₂Li(THF)₂ (4) and [LiBr{Li(THF)}₂{CoBr(OSiMe₃)₃}]₂ (5) form centrosymmetrical halogen-bridged dimers in the crystalline state. Compound 4 shows bromide bridges between lithium and cobalt, and silanolato bridges between the cobalt atoms. Below 200 K there are significant antiferromagnetic interactions between the cobalt centres. Compound 5 crystallises in a novel structure in which two cubane-like fragments containing silanolato bridges are linked together through a Li₂Br₂ ring.     

Factors influencing the DNA nuclease activity of iron, cobalt, nickel, and copper chelates

A library of complexes that included iron, cobalt, nickel, and copper chelates of cyclam, cyclen, DOTA, DTPA, EDTA, tripeptide GGH, tetrapeptide KGHK, NTA, and TACN was evaluated for DNA nuclease activity, ascorbate consumption, superoxide and hydroxyl radical generation, and reduction potential under physiologically relevant conditions. Plasmid DNA cleavage rates demonstrated by combinations of each complex and biological co-reactants were quantified by gel electrophoresis, yielding second-order rate constants for DNA(supercoiled) to DNA(nicked) conversion up to 2.5 × 10(6) M(-1) min(-1), and for DNA(nicked) to DNA(linear) up to 7 × 10(5) M(-1) min(-1). Relative rates of radical generation and characterization of radical species were determined by reaction with the fluorescent radical probes TEMPO-9-AC and rhodamine B. Ascorbate turnover rate constants ranging from 3 × 10(-4) to 0.13 min(-1) were determined, although many complexes demonstrated no measurable activity. Inhibition and Freifelder-Trumbo analysis of DNA cleavage supported concerted cleavage of dsDNA by a metal-associated reactive oxygen species (ROS) in the case of Cu(2+)(aq), Cu-KGHK, Co-KGHK, and Cu-NTA and stepwise cleavage for Fe(2+)(aq), Cu-cyclam, Cu-cyclen, Co-cyclen, Cu-EDTA, Ni-EDTA, Co-EDTA, Cu-GGH, and Co-NTA. Reduction potentials varied over the range from -362 to +1111 mV versus NHE, and complexes demonstrated optimal catalytic activity in the range of the physiological redox co-reactants ascorbate and peroxide (-66 to +380 mV).     

Anion-exchange separation of iron,cobalt and nickel

From 90% acetone-10% 6 M hydrochloric acid medium, cobalt and nickel are strongly adsorbed on the anion-exchange resin Dowex I-X8; iron is not adsorbed and can thus be separated from cobalt and nickel. Cobalt and nickel are then separated by elution with 70% acetone-30% 2 M hydrochloric acid; nickel is eluted before cobalt. The method can be applied to the determination of nickel and cobalt in materials with high iron content such as steels ; compleximetric titrations are used for the final step.     

Synthesis, structure and DFT study of dinuclear iron, cobalt and nickel complexes with cyclopentadienyl-metal moieties

Reactions of 1,1'-bis(dipheny1phosphino)cobaltocene with Co(PMe(3))(4), Ni(PMe(3))(4), Fe(PMe(3))(4), Ni(COD)(2), FeMe(2)(PMe(3))(4) or NiMe(2)(PMe(3))(3) afford a series of novel dinuclear complexes [((Me(3)P)[lower bond 1 start]Co(η(5)-C(5)H(4)[upper bond 1 start]PPh(2)))((Me(3)P)M[upper bond 1 end](η(5)-C(5)H(4)P[lower bond 1 end]Ph(2)))] (M = Co(1), Ni(2) and Fe(3)) [Co(η(5)-C(5)H(4)[upper bond 1 start]PPh(2))(2)Ni[upper bond 1 end](COD)](4), [Co(η(5)-C(5)H(4)[upper bond 1 start]PPh(2))(2)Ni[upper bond 1 end](PMe(3))(2)] (5) and [((Me(3)P)[lower bond 1 start]Co(Me)(η(5)-C(5)H(4)[upper bond 1 start]PPh(2)))((Me(3)P)Fe[upper bond 1 end](Me)(η(5)-C(5)H(4)P[lower bond 1 end]Ph(2)))] (6). Reactions of 1,1'-bis(dipheny1phosphino)ferrocene with Ni(PMe(3))(4), NiMe(2)(PMe(3))(3), or Co(PMe(3))(4) gives rise to complexes [Fe(η(5)-C(5)H(4)[upper bond 1 start]PPh(2))(2)M[upper bond 1 end](PMe(3))(2)] (M = Ni (7), Co (8)). The complexes 1-8 were spectroscopically investigated and studied by X-ray single crystal diffraction. The possible reaction mechanisms and structural characteristics are discussed. Density functional theory (DFT) calculations strongly support the deductions.     

Simultaneous kinetic determination of copper, cobalt and nickel by means of -group interchange reactions

The kinetic determination of copper, cobalt and nickel in binary and ternary mixtures without prior separation is described. The methods are based on the difference in the reaction rate of interchange of - groups between thiosemicarbazide and 6-methylpicolinaldehyde azine in the presence of these ions at pH 4.5. Through these reactions the corresponding metal thiosemicarbazone complexes are formed. Various ratios of these ions at the 10(-5)M level can be determined photometrically by either the logarithmic extrapolation method or a combined initial-rate and fixed-time method proposed here for the first time.     

Micellar colorimetric determination of iron, cobalt, nickel and copper using 1-nitroso-2-naphthol

1-Nitroso-2-naphthol, an excellent color-forming chelating agent, combines to Fe(III), Co(II), Ni(II), Cu(II) and so on to form slightly soluble complexes in aqueous solution. To determine these metal ions, a tedious and time consuming separation technique, such as liquid-liquid extraction, has often been performed. However, these metal-1-nitroso-2-naphthol complexes could be determined conveniently by ultraviolet-visible (UV-Vis) spectrophotometry in Tween 80 micellar medium that has polyoxyethylene groups. After conditions such as pH, the amount of 1-nitroso-2-naphthol and the stability were adjusted to their optimum values, the sensitivities of the metal ions in Tween 80 medium and in chloroform were compared. It was shown that the sensitivities of Fe(III) and Co(II) in Tween 80 medium were higher than in chloroform, but that of Cu(II) was lower. The interfering effects among analytes ions, Fe(III), Co(II), Ni(II) and Cu(II) were more serious than by other ions, but the interfering effects could be removed by adjusting pH or adding the masking agents such as NH(3) or oxalate. Detection limits of Fe(III), Co(II), Ni(II), and Cu(II) were 0.024, 0.016, 0.039 and 0.023 mug ml(-1), respectively, and the correlation coefficients of these calibration curves were above 0.996. Recovery yields of the metal ions in the mixed standard solution ranged from 96 to 103%, and their coefficients of variation were low ranging between 0.94 and 1.75%. Cu(II) in brass sample and the amount of Fe(III) in steel sample were also determined. This proposed technique is simple, convenient and speedy.     

Synthesis and characterization of divalent manganese,cobalt, nickel,copper and zinc complexes with nicotinic acid

Coordination compounds of the transition metal(II) acetylacetonates of the formula [M(NA)₂(acac)₂ ]_n (M = Mn, Co, Ni, Cu and Zn; NA = nicotinic acid and acac = acetyl-acetonate anion) have been synthesized and characterized by chemical analysis, magnetic susceptibility, ligand-field spectra, IR and far-IR spectral measurements as well as photoacoustic spectroscopy in the solid state. Tentative stereochemistries for the complexes isolated in the solid state are suggested. The ligand-field parameters 10 Dq, B, β, λ and CFSE are calculated for cobalt and nickel complexes and are in good agreement with the proposed geometries. The metal ions attain six-coordination through the four oxygens of the anion and two donor atoms of the nicotinic acid ligands acting always as monodentate ligands. The formation of the compound results in a considerable shift of v(M-O) to lower frequencies in all the compounds related to parent acetylacetonates.