Mechanism of N-vinylcarbazole polymerization on Co(II)–13X molecular sieve

Kinetics of polymerization of N-vinylcarbazole over Co(II)-13X molecular sieves in toluene have been studied. The rate of polymerization (R_p) has been found to be second order with respect to percent exchange level of Co(II) and also to the NVC concentration at all the reaction temperatures of 40, 50 and 60°C. The rate increases with decreasing pH of the original exchanging salt solution up to a pH of about 3.5, beyond which it falls. The overall activation energy of polymerization has been found to decrease with increase in monomer concentration, exchange level of Co(II), and the hydrogen ion concentration of the original exchange solution. Average degree of polymerization also follows a similar trend. A mechanism of polymerization involving simultaneous propagation on both metal ion Co(II) and proton on a zeolite surface has been suggested. The two propagation routes are characterized by an average activation energy of 10.36 kcal/mol and 5.40 kcal/mol on the metal ion and proton centers, respectively.     

Host-guest chemistry of copper(II)-histidine complexes encaged in zeolite Y

Structural analysis has been carried out on copper(II )–histidine (Cu²⁺/His) complexes after immobilization in the pore system of the zeolites NaY and de‐aluminated NaY (DAY). The aim of this study was to determine the geometrical structure of Cu²⁺/His complexes after encaging, to obtain insight into both the effect of the zeolite matrix on the molecular structure and redox properties of the immobilized complexes. In addition to N₂ physisorption and X‐ray fluorescence (XRF) analyses, a combination of UV/Vis/NIR, ESR, X‐ray absorption (EXAFS and XANES), IR, and Raman spectroscopy was used to obtain complementary information on both the first coordination shell of the copper ion and the orientation of the coordinating His ligands. It was demonstrated that two complexes ( A and B ) are formed, of which the absolute and relative abundance depends on the Cu²⁺/His concentration in the ion‐exchange solution and on the Si/Al ratio of the zeolite material. In complex A , one His ligand coordinates in a tridentate facial‐like manner through N_am, N_im, and O_c, a fourth position being occupied by an oxygen atom from a zeolite Brønsted site. In complex B , two His ligands coordinate as bidentate ligands; one histamine‐like (N_am, N_im) and the other one glycine‐like (N_am, O_c). In particular the geometrical structure of complex A differs from the preferred structure of Cu²⁺/His complexes in aqueous solutions; this fact implies that the zeolite host material actively participates in the coordination and orientation of the guest molecules. The tendency for complex A to undergo reduction in inert atmosphere to Cu¹⁺ (as revealed by dynamic XANES studies) suggests activation of complex A by the interaction with the zeolite material. EXAFS analysis confirms the formation of a distorted four coordinate geometry of complex A , suggesting that the combination of zeolite and one His ligand force the Cu²⁺ complex into an activated, entactic state.     

Homogeneous isotope exchange between copper(II) and bis(resacetophenone oxime)copper(II) complex

Isotope exchange behavior of bis(resacetophenone oxime)copper(II) complex with copper(II) in tri-n-butyl-phosphate and methanol medium has been studied. The studies were carried out at different temperatures varying the concentration of both metal ion and complex. The results show that the complex is labile in the kinetic sense. Increase in temperature increases the isotope exchange rate. The increase in concentration also results in enhancement of the rate of reaction.     

New inclusion compound — copper(II) hexacyanoferrate in faujasite

The copper(II) hexacyanoferrate lattice is formed within the zeolite when CuSO₄ reacts with hexacyanoferrate (II) encapsulated in faujasite under hydrothermal conditions. A quantity, of Cu²⁺ in excess of that necessary for ion exchange has an important role in forming the three dimensional structure, apparently through interactions with the zeolite skeleton. Formation of the hexacyanoferrate is accompanied by considerable deformation of the faujasite skeleton.L. V. Pisarzhevskii Institute of Physical Chemistry, Ukraine National Academy of Science, Ukraine, 252039 Kiev, Nauki Prospekt 31. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. 1, pp. 43–46, January–February, 1996. Original article submitted April 27, 1995.     

Electroninitiated polymerization of bis(trichlorophenoxo)-tetramethylethylene diamine copper(II)

Electroninitiated polymerization of bis(trichlorophenoxo)-N,N,N′,N′-tetramethylethylene diamine copper(II) was achieved in acetonitrile at various peak potentials of the monomer. A constant potential approach was selected in polymerization reactions. Electrolyses were carried out under air, nitrogen, and oxygen atmospheres. Structural analyses of the polymers were done by ¹H-NMR and ¹³C-NMR FT–IR spectroscopy. Molecular weights of the polymers were determined by vapor pressure (isopiestic) method.     

Spectroscopic investigation of the cobalt(II), nickel(II), copper(II) and zinc(II) tetrahalometallates of theN-ethylmorpholinum cation

Summary Tetrahalometallates of the type (Etmorphl1)21MX4 (M = Co¹¹, Ni¹¹ or Zn¹¹ and with X = Cl, Br or l; M = Cu^II with X = CI or Br) and mixed tetrahalocuprates, Etmorphll)₂[CUX_mY_4–m] (X = Cl; N' = 13r; m = 1,2,3) of theN-ethylmorpholinium cation were prepared and investigated by means of spectroscopic and magnetic measurements. While the cobalt(II), nickel(II) and zinc(II) complexes appear to be essentially, tetrahedral, the copper(II) complexes are discussed on the basis of a distorted ('flattened') tetrahedral symmetry. The electronic spectra of the complexes are assigned on this basis. The far i.r. spectra of the complexes show bands which are unambiguously assignable to the metal-halogen stretching modes. The effects of the counter cation on the geometry around the metal ion, compared with that of the morpholinium and piperidinium cations, are discussed in relation to the pK_a of the amine.     

Chromotropism studies on copper(II) compounds. Part II. Dinuclear copper(II) complexes with triply-bridged hydroxo,acetate, and halo ligands

Abstract

Two triply-bridged dinuclear copper(II) complexes of formula [LCu(μ-OH)(μ-OAc)(μ-X)CuL]X?0.5H₂O where L is a bidentate ligand of N-(pyridine-2-ylmethyl)propane-2-amine and X=Cl, 1 and Br, 2 were synthesized and characterized by elemental analyses, spectroscopic techniques (IR, UV–Vis, EPR), thermal analysis, conductance measurements, and single-crystal X-ray structure determination. The structures of both complexes are similar. The complexes show a distorted square-pyramidal arrangement around each copper(II) ion with a CuN₂O₂X chromophore in which both copper(II) ions are connected by a hydroxo bridge and a triatomic syn-syn carboxylato bridge in equatorial positions and a halide ion bridge at the axial site. The chromotropism behavior of the complexes, including solvato-, thermo-, and halochromism, were investigated in detail. Their halochromism was investigated in the pH range of 2.0–11.0 by visible absorption spectroscopy. The reversible color variations from blue to colorless are attributable to deprotonation and protonation of the ligands. The complexes show reversible thermochromism in solution due to dissociation and recombination of ligands to copper ions.     

Homogeneous isotope exchange between copper/II/ and copper/II/-resacetophenone phenylhydrazone complex

Isotope exchange of copper/II/ between bis/resacetophenone phenylhydrazone/ copper/II/ complex and copper/II/ in trin-butyl phosphate and methanol medium was studied. The experiments were carried out at different temperatures varying the concentration of both metal ion and the complex. The results show that the complex is kinetically labile. An increase in temperature increases the rate of isotope exchange. The increase in concentration also results in the enhancement of the rate of reaction.     

Needle-type colloidal copper (II)hydroxide particles

Stable dispersions of fine (< 0.05m) needle-type copper(II) hydroxide particles were prepared at room temperature by admixing sodium acetate and ammonia to copper sulfate solution. The particle length and width could be altered with the concentration of reactants. The rate of dissolution of copper(II) hydroxide particles in doubly distilled water at room temperature is time dependent, which is due in part to the formation of a mononuclear complex solute (CuOH⁺). After extended times (e.g., 18 h), the particles underwent phase transformation, resulting in longer needles of higher degree of crystallinity.Supported by the Griffin Corp., Valdosta, Georgia.     

Synthesis and characterization of 7,16-dinicotinoyl- and 7,16-diisonicotinoyltetraaza[14]annulene and their nickel(II) and copper(II) complexes

The reaction of tetraaza[14]annulene and its complexes with nicotinoyl chloride hydrochloride and/or isonicotinoyl chloride hydrochloride produced the 7,16-dinicotinoylated and/or 7,16-diisonicotinoylated corresponding products in satisfactory yields. The mass spectra reveal the molecular ion peaks due to the 7,16-diacylated products. A strong ir band which is correlated with a C = 0 stretching mode is freshly observed in the 1635–1670 cm^?1 region upon the acylation. The electronic spectra for the complexes hardly change upon the acylation, but those for the ligands change slightly. The olefinic proton signals at the 7- and 16-positions disappear on the acylation in ¹H-nmr spectra and the substituted pyridine proton signals are newly observed. The proton nmr results are consistent with those of the carbon-13 nmr. The spin Hamiltonian parameters for the acylated copper(II) complexes are comparable with those for the copper(II) complex which is not acylated. The copper(II) complexes assume the square-planar coordinations with an unpaired electron in the d_x2_?y2 orbital.     

Electrochemical behavior of Ni(II) incorporated in zeolite Y-modified carbon electrode: application for electrocatalytic oxidation of methanol in alkaline solution

Nickel ions were incorporated in NaY zeolite according to cation exchange mechanism. Then NiY zeolite was used as modifier for preparation of modified carbon paste electrode. The electrochemical behavior of NiY-modified carbon paste electrode (NiY/CPE) was studied in alkaline solution using cyclic voltammetry method. Ability of different electrodes containing NiY/CPE, Ni-NiY/CPE, Ni-NaY/CPE, and Ni/CPE for electrocatalytic oxidation of methanol was compared (three last electrodes prepared by open circuit accumulation of Ni(II) ions on the surface of NiY/CPE, NaY/CPE, and bare CPE, respectively). Results show that Ni-NiY/CPE is best catalyst for the electrochemical oxidation of methanol in alkaline solution and both process of earlier Ni ion incorporation through cation exchange in NaY zeolite and open circuit accumulation of Ni ion on the surface of electrode are essential to have good catalyst. Effect of graphite–zeolite ratio on electrocatalytic current was studied and 3:1 ratio of graphite–zeolite was selected as optimum ratio for preparing electrode. Ni-NiY/CPE has very good stability toward the methanol oxidation in concentration range of 0.005 to 0.5 M. Finally, using chronoamperometric method, the catalytic rate constant (k) for methanol was found to be 1.56 × 10⁴ cm³ mol⁻¹ s⁻¹.     

Binuclear copper(II) complexes of 5-nitrosalicylaldehyde N(3)-substituted thiosemicarbazones

Summary Binuclear copper(II) complexes with six 5-nitrosalicylaldehyde N(3)-substituted thiosemicarbazones have been prepared and characterized. I.r., electronic and e.s.r. spectra of the complexes, as well as i.r., electronic, and ¹H-and ¹³C-n.m.r. spectra of the thiosemicarbazones, have been obtained. The crystal structure of a monomeric copper(II) complex of 5-nitrosalicylaldehyde piperidyl-thiosemicarbazone, H₂5NO₂Sapip, grown from DMF solution, has been solved. Neither the thiosemicarbazones or their binuclear copper(II) complexes show growth inhibitory activity against Aspergillus niger, but the copper(II) complexes show some activity against the fungus Paecilomyces variotii.     

Preparation of the thermosensitive metal ion imprinted polymer in supercritical carbon dioxide: application in the selective recognition of copper (II)

The temperature‐sensitive Cu(II) ion imprinted polymer (Cu(II)‐MIIP) materials were prepared via precipitation polymerization methods in supercritical carbon dioxide (scCO₂) by using methanol as cosolvent. In the polymerization process, the polymerization mixture consists of copper ion, N‐isopropylacrylamide (functional monomer), ethylene glycol dimethacrylate (crosslinker), and 2,2′‐azobisisobutyronitrile (initiator). Non‐imprinted polymer particles were similarly prepared in the same way except for the presence of copper ion in the polymerization reaction. In this study, the characteristic of swelling/shrinking for Cu(II)‐MIIP in response to the change in temperature was investigated by scanning electron microscopy and photograph of swelling/shrinking for Cu(II)‐MIIP in deionized water. The above‐synthesized polymer particles were characterized by using Fourier transform infrared, thermo‐gravimetric analysis, and X‐ray diffraction techniques. Furthermore, the complete removal of the copper metal ion from the CuP was confirmed by atomic absorption spectroscopy. The selectivity adsorption of polymer materials was investigated from dilute aqueous solutions, and it was found to have an imprinting efficiency of 2.13 for Zn and Co ions. Copyright © 2011 John Wiley & Sons, Ltd.     

Electrochemical solid-phase nanoextraction of copper(II) on a magnesium oxinate-modified carbon paste electrode by cyclic voltammetry

Solid-phase nanoextraction is a sample preparation technique, which combines nanotechnology with analytical chemistry, and brings analytical chemistry to a higher level, particularly for complex system analysis. This paper describes a typical example of electrochemical solid-phase nanoextraction and electrochemical detection. Trace amounts of copper (5.0?×?10^?13?mol/L) were extracted by electrochemical solid-phase nanoextraction on to the magnesium oxinate nanoparticle-modified carbon paste electrode surface in a pH?7.2 phosphate buffer system at ?0.50 V for 100 s. The extraction is achieved by the cation exchange between copper(II) in the aqueous solution and magnesium(II) from the magnesium oxinate nanoparticles on the electrode surface. The extracted copper shows an irreversible anodic peak at about 0.2 V (vs. saturated calomel electrode). The peak current is proportional to the scan rate, which shows this to be a surface-controlled process. The oxidation peak current is proportional to the logarithm of the copper concentration in the range 5.0?×?10^?13?～?5.0?×?10^?7?M with a slope of 2.215. This powerful method uses the carbon paste electrode to combine extraction with electrochemical analysis.     

Separation of copper(II) and aluminium(III) from fresh waters by solid phase extraction on a complexing resin column

The solid‐phase extraction (SPE) of copper(II) and aluminium(III) from fresh waters on an ion‐exchange complexing resin containing iminodiacetic groups (Chelex 100) has been examined. Quantitative recovery of the metal ions was related to the breakthrough profile that, for some samples, could not be evaluated directly. A method is suggested for evaluation, instead, of the sorption curves, on the basis of passing different volumes of sample through the column. This enables evaluation of important properties, for instance the central point of the breakthrough curve, V_f. The column used was a small one, containing 0.10 g dry Chelex 100. The metal ion was eluted with a small volume of acid solution, 10 mL of 0.5 mol L^–1 HNO₃; this resulted in good preconcentration factors. For copper(II) it was found that fresh waters of similar composition could have different V_f in the same column. This was ascribed to different reaction coefficients (α_M(I)) of copper(II) in the considered samples, which affects V_f. By use of the proposed SPE procedure it is possible to evaluate the reaction coefficient of copper(II). The values of α_M(I) for two different drinking waters at pH 7.7 were found to be 3.70×10¹² and less than 4.40×10¹¹. Similar results were obtained for aluminium(III).     

Synthesis and spectral studies of copper(II), nickel(II), cobalt(II) and vanadyl(II) complexes of tridentate Schiff bases of 1,2,3,5,6,7,8,8a-octahydro-3-oxo-N,1-diphenyl-5-(phenylmethylene)-2-naphthalenecarboxamide

Summary Metal(II) chelates of Schiff bases derived from the condensation of 1,2,3,5,6,7,8,8a-octahydro-3-oxo-N,1-diphenyl-5-(phenylmethylene)-2-naphthalenecarboxamide with o-aminophenol (KAAP), o-aminothiophenol (KAAT) or o-aminobenzoic acid (KAAB) have been prepared and characterized. The complexes are of the type [M(N₂X)]₂ for M = Cu^II and M(NX)₂·nH₂O for M = Ni^II, Co^II and VO^II (X = phenolic oxygen, thiophenolic sulphur or carboxylic oxygen; n = 0 or 2). Conductivity data indicate that the complexes are non-ionic. The Schiff bases behave as dibasic tridentate ligands in their copper(II) complexes and as monobasic bidentate ligands in their nickel(II), cobalt(II) and vanadyl(II) complexes. The subnormal magnetic moments of the copper(II) complexes are ascribed to an antiferromagnetic exchange interaction arising from dimerization. Nickel(II) and cobalt(II) complexes are trans octahedral whereas vanadyl(II) complexes are square pyramidal     

CopC protein from Pseudomonas syringae: intermolecular transfer of copper from both the copper(I) and copper(II) sites

The CopC protein from Pseudomonas syringae pathovar tomato is expressed as one of four proteins encoded by the operon CopABCD that is responsible for copper resistance. It is a small soluble molecule (10.5 kDa) with a beta-barrel structure and features two distinct copper binding sites, which are highly specific for Cu(I) (K(D) > or = 10(-)(13)) and Cu(II) (K(D) approximately 10(-)(15)). These dissociation constants were estimated via ligand competition experiments monitored by electronic spectral and fluorescence probes. The chemistries of the two copper sites are interdependent. When the Cu(II) site is empty, the Cu(I) ion is oxidized by air, but when both sites are occupied, the molecule is stable in air. The availability of an unoccupied site of higher affinity induces intermolecular transfer of either Cu(I) or Cu(II) while maintaining free copper ion concentrations in solution at sub-picomolar levels. This intriguing copper chemistry is consistent with the proposed role of CopC as a copper carrier in the oxidizing periplasmic space. These properties would allow it to exchange either Cu(I) or Cu(II) with its putative partners CopA, CopB, and CopD, contrasting with the role of the Cu(I) (only) chaperones found in the reducing cytoplasm.     

Synthesis and structures of copper(II) and nickel(II) complexes of 1,8-diaza-4-thiaoctane. Characterization of a novel polymeric trigonal bipyramidal copper(II) complex containing both bridging and meridionally coordinated ligands

Summary The synthesis, x-ray structure determination, and spectroscopic properties of nickel(II) and copper(II) complexes of 1,8-diaza-4-thiaoctane (aeaps) are described. [Ni(aeaps)₂](ClO₄)₂ crystallizes in the orthorhombic space group Pbcn witha=10.943(2),b=13.209(2),c=14.798(2)Å, and Z=4. The complex crystallizes as the unsymmetrical facial isomer, with the sulfur atoms incis positions. The copper(II) complex crystallizes in the monoclinic space group Cc, witha=16.041(2),b=9.223(1),c=16.048(3) Å,a=118.65(2)⁰, and Z=4. The copper(II) ion has a trigonal bipyramidal coordination geometry, with one ligand coordinated meridionally, and two bridging ligands in which the thioether is not bound to a metal ion. The structures of these complexes are discussed in terms of the known solution chemistry of this ligand with copper(II) and nickel(II).     

Synthesis and magnetic properties of the novel binuclear copper(II) metallochelates with unsymmetrical exchange fragment including heterocyclic derivatives

The series of the novel copper(II) binuclear metallochelates with unsymmetrical exchange fragment including pyrazolate bridge has been synthesized for the first time. The composition and structure of the prepared compounds have been established with the data of UR, NMR-H¹, EXAFS spectroscopy as well as magnetochemical studies. The analysis of the influence of pyrazolate ion on the magnetic exchange interaction between two copper atoms has been carried out.