Complexation behavior of Schiff base toward transition metal ions

Complexes of Iron, Cobalt, Nickel and Zinc ions with the Schiff base derived from p-dimethylaminobenzaldehyde and o-aminobenzoic acid were synthesized and investigated by several techniques using elemental analyse (C,H,N), molar conductance measurements, infrared and electronic spectra. The elemental analysis data suggest the stoichiometry to be 1:1 [M:L] ratio formation. The molar conductance measurements reveal the presence of non-electrolytic nature complexes. Infrared spectral data agreed with the coordination to the central metal ions through both the nitrogen atom of the azomethine and oxygen atom of the carboxyl group of the 2-aminobenzoic acid moiety. The electronic spectral data suggest the existence of octahedral geometry for Fe(III) complex, square planar geometry for Co(II) and Ni(II) complexes and tetrahedral geometry for Zn(II) complex.     

Complexation of polymethacrylopiperidide with transition metal ions in aqueous solution

The interactions of polymethacrylopiperidide with Cu²⁺, Ni²⁺, Co²⁺ and Fe³⁺ ions have been investigated by potentiometric and conductometric titration, ESR and u.v. spectroscopy, viscometry and sedimentation. The average number of ligands coordinating with the central metal ions and the stability constants of polymeric metal complexes were determined. It is assumed that the polymethacrylopiperidide interacts with transition metal ions through the nitrogen atoms. The influence of spatial arrangement of donor atoms on the coordination ability of polyligand is discussed.     

Complexation of heterocyclic azo compounds with transition metal ions as found by the laser-induced desorption/ionization method

The Pd, Mn, La, and Rh complexes with the heterocyclic azo compounds were studied by the laser-induced electron transfer desorption/ionization (LETDI) method. The optimum parameters of laser irradiation were found, and the compositions of the complexes were determined. The quantum chemical simulation of the compositions of the complexes was performed on the basis of the data of mass spectrometry. It is shown that laser-induced electron transfer desorption/ionization is an effective tool for the high-sensitive determination and identification of metal complexes.     

Polyoxometalate tri-supported transition metal complexes containing mixed-valent transition metal ions

Three compounds, [AsMo₈V₆O₄₂][Cu(2,2?-bpy)₂]₂[Cu(2,2?-bpy)]·4H₂O (1), [PMo₈V₆O₄₂][Cu(2,2?-bpy)₂]₂[Cu(2,2?-bpy)]·3H₂O (2) and [PMo₈V₆O₄₂][Cu(2,2?-bpy)₂]₂[Cu(2,2?-bpy)]·3.5H₂O (3), have been synthesized under hydrothermal conditions and characterized by IR, UV–vis, XRD, TG, elemental analysis, and X-ray diffraction analysis. Single-crystal X-ray structure analysis reveals that 1 and 2 are isostructural and isomorphous, whereas 2 and 3 are polymorphs. Polymorphs of 1 have not been synthesized yet. The mixed-valent transition metal ion in 1–3 has been further confirmed by TG analyses. Catalytic properties of 1 and 2 have also been studied.     

Complexation of diazaperylene and bisisoquinoline with transition metal ions in the gas phase studied by electrospray ionization mass spectrometry

The complex formation of the ligands 1,12-diazaperylene (dap), 1,1'-bisisoquinoline (bis), 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen) with transition metal ions (M = Fe, Co, Ni, Cu, Zn, Ru, Os, Re, Pd, Pt, Ag and Cd) in the gas phase has been studied by electrospray ionization mass spectrometry. With the exception of Ru, Os, Fe, Ni and Cu, singly charged complexes [MLn](+) (n = 1,2) were observed. The complexes of dap and bis with Ru, Os, Fe and Ni ions, and the mixed ligand complexes with bpy and phen, are preferably of the doubly charged type [ML3]2+. In addition, collision-induced dissociation (CID) measurements were employed to evaluate the relative stabilities of these complexes. The CID experiments of mixed-ligand complexes which contain both dap and phen or dap and bpy exhibit preferential elimination of bpy, indicating that bpy is a weaker ligand than phen and dap.     

过渡金属离子与明胶相互作用的研究

利用荧光猝灭法,研究了pH值10.0,不同温度下,Mn^2+,Co^2+,Ni^2+,Hg^2+与明胶的相互作用。计算了猝灭常数、螯合平衡常数和结合位点数。紫外光谱和显微红外光谱的测定结果表明,Mn^2+,Co^2+,Ni^2+与明胶分子中的酰胺键发生了作用。确定了猝灭机理。计算得出的热力学函数表明,在Mn^2+,Co^2+,Ni^2+对明胶荧光的猝灭过程中,熵效应起着重要的作用。     

Detailed crossover studies of transition metal ions

The complete ligand field, interelectronic repulsion, and spin-orbit interaction matrices were solved for the octahedral and tetrahedrald ⁴ andd ⁶ electron configurations. The results are employed in a detailed study of the crossover region. It is demonstrated that, close to the crossover, complicated mixing and interaction patterns may arise. A sharp crossover is encountered in the octahedrald ⁶ system exclusively where ₁ and ₅ levels are involved. In all situations where the two ground levels transform according to the same irreducible representation, the crossover is redefined by that value of 10Dq where both ground terms participate in the lowest level to equal amounts.

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Zusammenfassung Die vollständigen Matrizen des Ligandenfeldes, der Elektronenwechselwirkung und der Spin-Bahn-Kopplung wurden für die Elektronenkonfigurationend ⁴ undd ⁶ in Feldern oktaedrischer und tetraedrischer Symmetrie diagonalisiert. Die Ergebnisse werden in einer eingehenden Untersuchung des crossover-Bereiches eingesetzt. Es wird gezeigt, daß komplizierte Mischungs- und Wechselwirkungsstrukturen in der Nähe des Überschneidungspunktes der Grundterme auftreten können. Ein scharfer Schnittpunkt wird allein im oktaedrischend ⁶-System erhalten, wobei die Niveaus ₁ und ₂ unmittelbar beteiligt sind. In allen Fällen, in denen sich die zwei tiefsten Niveaus der zwei Grundterme nach derselben irreduziblen Darstellung transformieren, wird der Überschneidungspunkt durch denjenigen Wert von 10Dq neu definiert, bei dem beide Grundterme zum tiefsten Niveau zu gleichen Teilen beitragen.

     

Complexation of decamethylcucurbit[5]uril with alkali metal ions

Four coordination compounds, namely [Na(H₂O)(H₂O)₂⊂C₄₀H₅₀N₂₀O₁₀](C₆H₆O₂)₂Cl·8H₂O (1), [K₂(H₂O)₂(H₂O)⊂C₄₀H₅₀N₂₀O₁₀](C₆H₆O₂)₂Cl₂·7H₂O (2), [Rb₂(H₂O)₂(H₂O)⊂C₄₀H₅₀N₂₀O₁₀](C₆H₆O₂)₂Cl₂·7H₂O (3) and [Cs(H₂O)₂(H₂O⊂C₄₀H₅₀N₂₀O₁₀)](C₆H₆O₂)₂Cl·6H₂O (4), were obtained by the reactions of the corresponding alkali metal salts with decamethylcucurbit[5]uril (Me₁₀Q[5]) in the presence of hydroquinone, and their structures were determined by single-crystal X-ray diffraction. The results revealed that in compounds 1 and 4 each Me₁₀Q[5] ligand coordinates one Na⁺ or Cs⁺ ion to form a molecular bowl structure, while in compounds 2 and 3 each Me₁₀Q[5] ligand coordinates two K⁺ or Rb⁺ ions to form a closed molecular capsule structure, and adjacent molecular capsules bridge each other through water molecules to form 1D coordination polymers. In addition, we found that the coordination distances for the metal ions and the height of the metal ions out-of-portal-plane for the four compounds are in the same order, 1 < 2 < 3 < 4, which is attributed to the fact that the radius of alkali cations is in the order Na⁺ < K⁺ < Rb⁺ < Cs⁺. Although each portal of Q[6] binds with two alkali cations (not including Cs⁺), the Q[6]-based alkali cations complexes display similar structural trends.     

New bis-macrocyclic complexes with transition metal ions

Template condensation of benzidine, formaldehyde, ethylenediamine or 1,3-diaminopropane, metal salt and 1-phenyl-1,3-butanedione or 2,3-butanedione in a 1:4:2:2 molar ratio results in the formation of two new series of binuclear pentaaza macrocyclic complexes: dichloro[1,1-phenylbis(7-methyl-9-phenyl-1,3,6,10,13-pentaazacyclotetradeca-6,9-diene) metal(II)], [M₂LCl₄] (M = Co^II, Cu^II, Fe^III and Zn^II) and dichloro[1,1-phenylbis(8,9-dimethyl-1,3,7,10,14-pentaazacyclopentadeca-7,9-diene) metal(II)], [M₂LCl₄] (M = Ni^II, Co^II, Cu^II and Cd^II). Both series were characterized by i.r., ¹H-n.m.r., u.v.–vis. spectral studies, conductivity and magnetic susceptibility measurements.     

Effect of gamma-radiation on Methanosarcina hydrogenase containing transition metal ions

Tracer studies using⁶⁵Zn and⁵⁸Co showed that of the four forms ofMethanosarcina hydrogenases, the A form has about 15% of acid labile zinc, while the hydrogenase D has about 50% of cobalt of the total bound activity in the cell and the other two forms B and C have neither zinc nor cobalt. However, all hydrogenases are known to contain iron, sulfur and probably nickel in trace amounts. All air-oxidized forms of hydrogenases catalyze the reduction of methyl viologen after a finite incubation period. The reduction is revealed by an increase in the absorption peak at 602 nm. On -irradiation, all the four hydrogenases changed to more stable oxidized forms, as indicated by an increase in the optical absorption in the visible region at 405 nm. The irradiated samples showed a greater time lag before they could reduce methyl viologen, the time lag increasing with the -dose. The irradiated enzymes could be reactivated by flushing with H₂. The zinc-bearing hydrogenase A alone appeared to be immune to -radiation in its ability to reduce methyl viologen. This may be due to the zinc having no unpaired electrons to interact with -radiation or the primary radiolytic products.     

Peculiarities of cyanide-faujasite systems incorporating transition metal ions

Fragments of the corresponding hexacyanoferrates are formed when transition metal ions replace Na⁺ in faujasite containing hexacyanoferrate(II) encapsulated in the large pores.Translated from Teoreticheskaya i Èksperimental'naya Khimiya, Vol. 30, No. 6, pp. 332–336, November–December, 1994.     

Chelation of transition metal ions by peptide nanoring

We have computationally studied the energetics and electronic structures of a chelate system where the guest cation is a transition metal (TM) and the host ligand is a peptide nanoring (PNR). The trapping of a TM cation by a cyclic peptide skeleton is primarily caused by the electrostatic interaction. The exchange interaction plays a secondary role in determining the relative stability in accordance with the spin multiplicity. An interesting feature of this chelate system is that a TM cation can also be trapped by the side-chain aromatic groups of the PNR via pi-d hybridization. However, the spin multiplicity of the system changes the trapped form. When the chelate system has spin singlet multiplicity, a Fe(2+) cation, for example, is not trapped by the single-phenyl group but is preferentially sandwiched by the two phenyl groups. In contrast, a Fe(2+) cation can be trapped by single as well as by double-phenyl groups when the chelate system has higher spin multiplicity, such as triplet and quintet. These two different trapping forms are caused by the difference in the number of valence electrons of TM cations. For this chelate system, the newly occupied molecular orbital (MO) has an interbenzene antibonding character. Therefore, an electron occupying this MO state favors the mutual separation of two benzene molecules. Because the electron occupation of this MO varies in accordance with the spin multiplicity, one can predict the preference for the single-phenyl-group trapping process rather than the double-phenyl-group process systematically as well as consistently.     

Catalytic activity of a zirconium(IV) oxide surface supported with transition metal ions

The kinetics of H₂O₂ decomposition have been investigated using ZrO₂ supported with transition metal ions including Cu^II, Ag^I, Hg^II, Co^II, Mn^II, Ni^II and Fe^III. At pH = 6.8, the reaction rate exhibits a first order dependence on the initial H₂O₂ concentration at low concentrations. The order of activity of the different catalysts is strongly dependent on the [H₂O₂]₀ used. The reaction proceed via the formation of the peroxo-intermediate which has an inhibiting effect on the reaction rate. The rate increases with increasing pH, and attains a limiting rate at higher pH's. A reaction mechanism is proposed involving liberation of HO₂ radicals from the peroxo-intermediate as the rate-determining step.     

Double layer effects in the electroreduction of transition metal ions

Experimental data for the reduction of transition metal complex ions obtained recently at mercury and single-crystal gold electrodes are reviewed. It is shown that the effective charge on the reactant is generally not the same as the nominal charge, but that it may be found on a basis of an analysis of the kinetic data together with the appropriate double layer data. In addition, the effective charge on the product is usually smaller than the nominal value. As a result, the analysis of the double layer effect involves the construction of corrected Tafel plots, which differ significantly from those described in the early work of Frumkin. Dedicated to Professor Oleg A Petrii on the occasion of his 70th birthday and in honor of his significant contributions to the field of electrochemistry.     

Complexation of some phthalexons with metal ions: Determination of chromium and palladium

Conditions for the complexation of three new phthalexons with metal ions are studied. A selection of the qualitative and quantitative composition of a buffer solution is justified. Procedures are developed for the determination of chromium(III) and palladium(II) in industrial samples.     

Thermal studies on 2,6-xylyliminodiacetato compounds of some transition metal ions

Some new 2,6-xylyliminodiacetato compounds of Mn(II), Fe(III), Ni(III), Zn(II) and Cd(II) have been prepared in aqueous media. The thermal behaviour of these compounds has been studied by TG, DTG, and DSC techniques. Heats of dehydration have been calculated from the DSC curves.     

Complexation reactions of tetrathiomolybdate ions with binuclear molybdenum and rhenium metal cluster complexes

Conclusions Syntheses are reported for previously unknown hetero- and homometallic polynuclear thio complexes, (n-Bu₄,N)₂ (Mo₆S₂₀), (n-Bu₂₄N)₂)Re₂Mo₄S₁₆), and K₄(Mo₆S₁₆).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 192–194, January, 1987.     

Influence of transition metal ions on the textural properties of alumina and aluminasilicates

Accelerated phase transformations and chemical reactions of metastable aluminas and kaolinite, doped with Cu^{2 +}, Mn^{3 +}/Mn^{2 +} and Fe^{3 +}/Fe^{2 +} ions, are accompanied with accelerated decrease of surface area and pore volume values. The phenomena in metal ion doped samples are explained by a catalytic mechanism, in terms of the Jahn-Teller effect. This revised version was published online in June 2006 with corrections to the Cover Date.