Sorption of Some Metal Ions on Inorganic Electron and Ion Exchangers Based on Zirconium(IV)

Conditions of sorption of nonferrous metal ions on inorganic electron and ion exchangers based on zirconium(IV) were analyzed. The sorption capacity was evaluated as influenced by pH, concentration, and temperature of the contacting solutions and nature and chemical composition of the ion exchanger.     

A New PVC-Membrane Electrode Based on a Macrocyclic Ionophore for Selective Determination of Ni (II) Ions

A poly(vinyl chloride)-based membrane of 3,4:12,13-dibenzo-1,6,10,15-tetraazacyclooctadecane with sodium tetraphenyl borate (NaTPB) as an anion excluder and dibutylphthalate (DBP), dibutylbutylphosphonate (DBBP), tris(2-ethylhexyl) phosphate (TEHP) and tributyl phosphate (TBP) as plasticizing solvent mediator was prepared and investigated as a Ni(II)-selective electrode. The best performance was observed with the membrane having the ligand-PVC-TEHP-NaTPB composition 1:4:1:1, which worked well over a wide concentration range (2.82 ×10⁻⁶−1.00 × 10⁻¹ M) with a Nernstian slope of 30.5 mV per decade of activity between pH 2.5–7.5. This electrode showed a fast response time of 18 s and was used over a period of 4 months with good reproducibility (S=0.4 mV). The selectivity coefficient over mono-, di- and trivalent cations indicate excellent selectivity for Ni (II) ions over a large number of cations. Anions such as Cl⁻ and NO₃⁻ do not interfere and the electrode also works satisfactorily in a partially non-aqueous medium. It has been used successfully for determination of Ni (II) in real samples.     

Synthetic Inorganic Ion Exchangers. XIV Thin-Layer Chromatography of Metal Ions on Thorium Phosphate: Quantitative Separation of Au (III) from Several Metal Ions

Abstract

The analytical potential of thorium phosphate as an ion exchanger has been explored by thin layer chromatographic (TLC) technique. Binder-free thin layers of thorium phos -phate have been explored for several important binary and ternary separations. A TLC method has been developed for quantitative separation of microgram-quantities of Au(III) from several metal ions in pure butanol system.     

Ni(II) Ions May Target the Entire Melatonin Biosynthesis Pathway—A Plausible Mechanism of Nickel Toxicity

Nickel is toxic to humans. Its compounds are carcinogenic. Furthermore, nickel allergy is a severe health problem that affects approximately 10–20% of humans. The mechanism by which these conditions develop remains unclear, but it may involve the cleavage of specific proteins by nickel ions. Ni(II) ions cleave the peptide bond preceding the Ser/Thr-Xaa-His sequence. Such sequences are present in all four enzymes of the melatonin biosynthesis pathway, i.e., tryptophan 5-hydroxylase 1, aromatic-l-amino-acid decarboxylase, serotonin N-acetyltransferase, and acetylserotonin O-methyltransferase. Moreover, fragments prone to Ni(II) are exposed on surfaces of these proteins. Our results indicate that all four studied fragments undergo cleavage within tens of hours at pH 8.2 and 37 °C, corresponding with the conditions in the mitochondrial matrix. Since melatonin, a potent antioxidant and anti-inflammatory agent, is synthesized within the mitochondria of virtually all human cells, depleting its supply may be detrimental, e.g., by raising the oxidative stress level. Intriguingly, Ni(II) ions have been shown to mimic hypoxia through the stabilization of HIF-1α protein, but melatonin prevents the action of HIF-1α. Considering all this, the enzymes of the melatonin biosynthesis pathway seem to be a toxicological target for Ni(II) ions.     

三(2,2'-联吡啶)钌(II)在磷酸锆层状物中的组装及光物理性质

合成了两种层间距极其相近的层状材料Zr(HPO₄)₂•6H₂O(水合α-ZrP)和丁胺-磷酸锆的复合物(α-ZrP•BA), 将发光配合物 组装到层状物中使层间距从1.04 nm增大到1.52 nm. 与层状物相互作用后最大吸收峰均从452 nm (水溶液)红移到了462 nm. 在水合α-ZrP中, 最大发射峰位从610 nm蓝移到604 nm并且荧光强度是水溶液中的两倍多, 连续测定4 h以后, 的荧光强度仅仅下降了4%; 而与α-ZrP•BA相互作用后发射峰位从610 nm移动到了595 nm, 但荧光强度只是稍有增大, 4 h内强度下降了大约29%; 组装到水合α-ZrP中以后, 的激发态寿命从415 ns(水溶液)增大到787 ns (～95%), 在α-ZrP•BA中只增大到了747 ns (～89%). 这些结果表明层状物水合α-ZrP能够为 光物理性能的改善提供更加优良的微观环境.     

Superacids Based on Zirconium Dioxide

The synthesis of the superacidic materials SO ₄ ²⁻ /ZrO₂ and WO₃/ZrO₂ is examined. The structure of their acidic centers and their activity in the isomerization and acylation of hydrocarbons are discussed.__________Translated from Teoreticheskaya i Eksperimental’naya Khimiya, Vol. 41, No. 3, pp. 156–165, May–June, 2005.     

Molecular and electronic structures of one-electron oxidized Ni(II)-(dithiosalicylidenediamine) complexes: Ni(III)-thiolate versus Ni(II)-thiyl radical states

The dithiosalicylidenediamine Ni II complexes [Ni(L)] (R=tBu, R'=CH2C(CH3)2CH2 1, R'=C6H4 2; R=H, R'=CH2C(CH3)2CH2 3, R'=C6H4 4) have been prepared by transmetallation of the tetrahedral complexes [Zn(L)] (R=tBu, R'=CH2C(CH3)2CH2 7, R'=C6H4 8; R=H, R'=CH2C(CH3)2CH2 9, R'=C6H4 10) formed by condensation of 2,4-di-R-thiosalicylaldehyde with diamines H2N-R'-NH2 in the presence of Zn II salts. The diamagnetic mononuclear complexes [Ni(L)] show a distorted square-planar N2S2 coordination environment and have been characterized by 1H- and 13C NMR and UV/Vis spectroscopies and by single-crystal X-ray crystallography. Cyclic voltammetry and coulombic measurements have established that complexes 1 and 2, incorporating tBu functionalities on the thiophenolate ligands, undergo reversible one-electron oxidation processes, whereas the analogous redox processes for complexes 3 and 4 are not reversible. The one-electron oxidized species, 1+ and 2+, can be generated quantitatively either electrochemically or chemically with 70 % HClO4. EPR and UV/Vis spectroscopic studies and supporting DFT calculations suggest that the SOMOs of 1+ and 2+ possess thiyl radical character, whereas those of 1(py)2 + and 2(py)2 + possess formal Ni III centers. Species 2+ dimerizes at low temperature, and an X-ray crystallographic determination of the dimer [(2)2](ClO4)2.2 CH2Cl2 confirms that this dimerization involves the formation of a S-S bond (S...S=2.202(5) A).     

Thermal Decomposition of Ni(II) and Fe(III) Nitrates and their Mixture

The thermal decompositions of nickel(II) nitrate hexahydrate and iron(III) nitrate nonahydrate were followed. It was found that the final decomposition products were NiO at 623 K and Fe2O3 at 523 K, respectively. The two salts exhibited only endothermic peaks and a loss in mass until constant mass was attained. The decomposition reactions and the compounds corresponding to each reaction were established. A heating rate of 1 K min-1 revealed several intermediates; higher heating rates shifted the peaks to higher temperatures. The use of an air flow during decomposition shifted the reactions to lower temperatures. The DTA for the mixed salts was found to be an overlap and the TG a summation of the results for the two individual salts. At 773 K, the decomposition products were composed of three phases: NiO, Fe2O3 and NiFe2O4. When these products were heated to 1773 K, only NiFe2O4 was identified by X-ray diffraction. This revised version was published online in July 2006 with corrections to the Cover Date.     

二（胍基）锆配合物的合成和表征

Addition of one equivalent of LiN（i-Pr）2 or LiN（CH2）5 to carbodiimides, RN=C=NR [R=cyclohexyl （Cy）, isopropyl （i-Pr）], generated the corresponding lithium of tetrasubstituted guanidinates {Li[RNC（N R^′2）NR]（THF）}2 [R=i-Pr, N R^′2=N（i-Pr）2 （1）, N（CH2）5 （2）; R=Cy, N R^′2=N（i-Pr）2 （3）, N（CH2）5 （4）]. Treatment of ZrCl4 with freshly prepared solutions of their lithium guanidinates provided a series of bis（guanidinate） complexes of Zr with the general formula Zr[RNC（N R^′2）NR]2Cl2 [R=i-Pr, N R^′2=N（i-Pr）2 （5）, N（CH2）5 （6）; R=Cy, N R^′2=N（i-Pr）2 （7）, N（CH2）5 （8）]. Complexes 1, 2, 5-8 were characterized by elemental analysis, IR and ^1H NMR spectra. The molecular structures of complexes 1, 7 and 8 were further determined by X-ray diffraction studies.     

Crystal Structures of Ni(II) and Co(II) cis-Octahedral Complexes with 3-Imidazoline Nitroxide

NiL₂Bipy·1.5EtOH, CoL₂Bipy·1.5EtOH, and CoL₂Phen·0.5EtOH mixed-ligand complexes with a fixed cis` position of paramagnetic ligands (L = 4-(3',3',3'-trifluoro-2'-oxopropylidene)-2,2,5,5-tetramethyl-3-imidazolidine-1-oxyl) have been synthesized and studied by X-ray crystallography.     

Thermal decomposition of Ni(II) and Fe(III) acetates and their mixture

The thermal decomposition of the ferric and nickel acetate salts has been followed. It was found that the heating rate affects the decomposition steps. For a heating rate of 1 K min^–1 the product is either Fe₂O₃ or NiO. For a higher heating rate the suboxides are obtained and reoxidized again on further heating. The decomposition of the mixed salt is an overlap of the DTA for the separate salts but the decomposition reactions are shifted to lower temperatures.We would like to thank Prof. Dr. N. Afify, Phys. Dept., Fact. Science, Assiut University, for experimental assistance and valuable discussions.     

Large magnetic anisotropy in pentacoordinate Ni(II) complexes

Pentacoordinate complexes in which Ni(II) is chelated by the tridentate macrocyclic ligand 1,4,7-triisopropyl-1,4,7-triazacyclononane (iPrtacn) of formula [Ni(iPrtacn)X(2)] (X=Cl, Br, NCS) have relatively large magnetic anisotropies, revealed by the large zero-field splitting (zfs) axial parameters |D| of around 15 cm(-1) measured by frequency-domain magnetic resonance spectroscopy (FDMRS) and high-field high-frequency electron paramagnetic resonance (HF-HFEPR). The spin Hamiltonian parameters for the three complexes were determined by analyzing the FDMRS spectra at different temperatures in zero applied magnetic field in an energy window between 0 and 40 cm(-1). The same parameters were determined from analysis of HF-HFEPR data measured at different frequencies (285, 380, and 475 GHz) and at 7 and 17 K. The spin Hamiltonian parameters D (axial) and E (rhombic) were calculated for the three complexes in the framework of the angular overlap model (AOM). The nature and magnitude of the magnetic anisotropy of the three complexes and the origin of the influence of the X atoms were analyzed by performing systematic calculations on model complexes.     

Acid-Base Properties and Structural Features of Composite Ion Exchangers Based on KU-23 and KM-2p Cation Exchangers and Hydrated Zirconium Oxide

A method for introduction of hydrated zirconium oxide into macroporous cation exchangers KU-23 and KM-2p and the acid-base properties and structural features of the composite ion exchangers are described.     

Zirconium(IV) catalysis in perborate oxidation of iodide

Zirconium(IV) catalyzes perborate oxidation of iodide ion. In acidic solution the oxidation is zero order with respect to perborate, first order with respect to Zr(IV), independent of [H⁺] and exhibits Michaelis-Menten dependence on [I⁻]. Mechanistic pathway of the catalysis is discussed and a rate equation is derived.     

Glycoligands tuning the magnetic anisotropy of Ni(II) complexes

Two organic ligands based on a sugar-scaffold derived from galactose and possessing three O-CH(2)-pyridine pendant arms at the 3-, 4-, and 5-positions of the galactopyranose that act as chelates afford mononuclear complexes when reacted with a Ni(II) salt. The magnetization behavior in the form of M=f(H/T) plots suggests the presence of appreciable magnetic anisotropy within the two complexes. The analysis of the EPR spectra performed at two different temperatures (7 and 17 K) and at three frequencies (190, 285, and 380 GHz) leads to the conclusion that the anisotropy has a high degree of axiality (E/D=0.17 for the two complexes), but with a different sign of the D parameter. The spin hamiltonian parameters D and E were reproduced for the two complexes by using calculations based on the angular overlap model (AOM). The structural difference between the two complexes responsible of the sign of the D parameters was also determined using AOM calculations. A thorough analysis of the structures showed that the structural differences in the coordination sphere of the two complexes responsible of the different D parameter sign result from the nature of the sugar scaffolds. In complex 1, the sugar scaffold imposes an intramolecular hydrogen bond with one of the atoms linked to Ni(II); this arrangement leads to a distorted coordination sphere and positive D value, while the absence of such a hydrogen bond in complex 2 leads to a less distorted environment around the Ni center and to a negative D value.     

Thermoanalytical Investigation of Several Layered Zirconium Salts and their Derivatives Part II

The comparison of data of thermal analysis partly with XRD and/or analytical results permits determination of the exact quantity of crystal water of the investigated samples having quite different behaviour. The compositions of the samples were determined from the results of thermal analysis. Furthermore, the data help elucidate the behaviour of various crystalline materials and also their intercalates during heat treatment. This revised version was published online in July 2006 with corrections to the Cover Date.     

Predicting Compensation Voltage for Singly-charged Ions in High-Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS)

Correlation between compensation voltage (CV) and the m/z ratio of singly-charged ions was elucidated. The experimental data for various alkylammonium homologues and various pharmaceutical compounds were used to construct empirical calibration curves that were fit using commercial regression analysis software packages. The best fit equations were applied to calculate the CV differences (??CV) in pure N₂ and N₂/He 50/50 carrier gasses and CV values for a variety of compounds using only m/z values. The calculated values were in good agreement with experimental data and ??CV values exhibited a very strong correlation with m/z. Application of these empirical calculations may provide a powerful CV prediction tool for researchers using high-field asymmetric waveform ion mobility spectrometry (FAIMS) and increase the value of FAIMS as an analytical method.     

Ion imprinted adsorbent for the removal of Ni(II) from waste water: preparation,characterization, and adsorption

Abstract

In this paper, a selective nickel ions chelating adsorbents (Ni-CMCS) were prepared based on carboxymethyl chitosan by ion imprinting technique. Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) were used to investigate their physicochemical properties. Brunauer-Emmett-Teller (BET) analysis showed that the BET surface area of Ni-CMCS had a significant increase after ion imprinting process. The effects of pH value, contact time and initial concentration of Ni(II) were studied. The adsorption kinetics were investigated, which indicated that Ni-CMCS was better fitted with pseudo-second-order kinetic model (R² = 0.9991) with film diffusion process as rate controlling step. The adsorption isotherms study indicated that Langmuir model matched better with the experimental data for Ni-CMCS (R² = 0.9617). Besides, the maximum adsorption capacity calculated from the Langmuir equation was 82.78?mg g^?1. Moreover, the selectivity experiment suggested that Ni-CMCS had good selectivity in the presence of Co(II), Mn(II), or Cd(II). After used four cycles, Ni-CMCS kept great adsorption capacity.     

Application of the TPR method for the studies of Ni(II) in Chrysoprase

TPR method was used to elucidate the status of nickel ions in chrysoprase. Temperature profiles of chrysoprase samples were interpreted by comparing them with TPR curves of references. Two kinds of nickel species were identified in the studied samples. The first one is nickel in 2:1 layer silicates while the other is nickel in the extra-framework positions. Apparent activation energies (85±3 and 20±5 kJ mol⁻¹) which were obtained from TPR data support the above attribution. This revised version was published online in July 2006 with corrections to the Cover Date.