Synthesis,structure and luminescent properties of 3D lanthanide (La(III), Ce(III)) coordination polymers possessing 1D nanosized cavities based on pyridine-2,6-dicarboxylic acid

Two novel coordination polymers, namely, {[Ln₂(PDA)(HPDA) (H₂O)₄ClSO₄]·2H₂O}_n (Ln = La(III) and Ce(III) for complexes I and II, respectively) were synthesized through the reaction between pyridine-2,6-dicarboxylic acid (H₂PDA) and La(NO₃)₃·6H₂O and Ce₂(SO₄)₃·8H₂O under hydrothermal conditions. Both of these polymers possess 1D infinite nanosized cavities embedding guest water molecules. The complexes were characterized by elemental analyses, IR spectroscopy, thermal analyses and single crystal X-ray diffraction. Two compounds crystallize in orthorhombic system, space group Pna2(1). Both of the complexes exhibit 3D metal–organic framework structure, where SO₄^2? anions play as the bridge between 1D wavelike chains and the adjacent parallel pyridine rings were arranged through π–π interactions. The bi-bidentate coordination mode of SO₄^2? anion was observed. Luminescent emissions of complex I were measured in the solution of DMF at room temperature. In addition, the luminescent emissions of complex I showed certain selectivity among some metal ions.     

Investigation of the Interaction Between Cu2-x S +So Coatings and Pd(II) Ions by Cyclic Voltammetry and X-ray Photoelectron Spectroscopy

The interaction between Pd²⁺ ions and Cu_2-xS coating formed by three cycles and containing ~30 at.% of elementary S has been investigated by the methods of cyclic voltammetry and photoelectron spectroscopy (one cycle of coating formation includes treatment of the surface with Cu(I)+Cu(II) ammoniate solution, hydrolysis of the adsorbed copper compounds and sulphidation of copper oxygen compounds in Na₂S_n solution). After exposure of such a coating to Pd²⁺ ions (1.7 mM PdCl_2’ pH-2), an exchange as well as a redox interaction between the coating components and Pd²⁺ ions has been shown to occur. Due to this the amount of copper in the coating decreases from 2 to 4 times and that of sulphur from 1.5 to 5 times. The coating modified in such a way has been found to contain up to 75 at.% of palladium, ~90% of it being in a metallic state.

It has been determined that at the beginning S^o is bound into a soluble compound:

2Pd²⁺ + S^o + 3H₂O → 2Pd^o + H₂SO₃ + 4H⁺.

The Cu₂S present in the coating is considered to interact with Pd²⁺, with the formation of Pd⁰ and CuPdS_2’, while CuS reacts most likely according to the reaction:

CuS + 3Pd²⁺ + 3H₂O → 3Pd^o; + H₂SO₃ + Cu²⁺ + 4H⁺.

The Cu_2-xS +S^o coating formed on a dielectric and modified with Pd²⁺, contrary to the initial Cu_2-xS +S^o coating, can be plated with copper from any electrolyte for copper deposition.     

Structural and magnetic properties of metal complexes constructed by pyridine-2,6-dicarboxylate and 5-(4-bromophenyl)-2,4′-bipyridine

Pyridine-2,6-dicarboxylic acid reacts as the first ligand (L1) under hydrothermal conditions with different metal ions such as Co^II, Ni^II, and Cu^II to form two 1D polymeric complexes [M(L1)(L2)₂·H₂O]_n (M = Co²⁺ or Ni²⁺) and a tetranuclear cluster with formula [Cu₄(L2)₄(L1)₄]·2H₂O in the presence of 5-(4-bromophenyl)-2,4′-bipyridine as the second ligand (L2). Intramolecular interactions were observed in the three compounds, being antiferromagnetic in both cobalt and nickel 1D coordination polymers and ferromagnetic interaction in the tetranuclear copper cluster.     

Synthesis,characterization, conductivity,band gap and thermal analysis of poly-2-[(4-mercaptophenyl) imino methyl] phenol and some of its polymer–metal complexes

The oxidative polycondensation reaction conditions of 2-[(4-mercaptophenyl) imino methyl] phenol (4-MPIMP) was studied in an aqueous alkaline medium between 30 and 90 °C by using oxidants such as air O₂, NaOCl and H₂O₂. Polymer–metal complex compounds were synthesized from the reactions of poly-2-[(4-mercaptophenyl) imino methyl] phenol (P-4-MPIMP) with Cr³⁺, Co²⁺, Ni²⁺, Cu²⁺, Mn²⁺, Zn²⁺, Pb²⁺, Cd²⁺ and Zr⁴⁺ ions. The structures of these monomer and polymer were identified from UV–vis, FT-IR, ¹H NMR, ¹³C NMR and elemental analysis. While thermal analysis of P-4-MPIMP and polymer–metal complexes were made by TGA–DTA, the number-average molecular weight (M_n), weight-average molecular weight (M_w) and polydispersity index (PDI) values of this polymer were determined by size exclusion chromatography (SEC). According to TG–DTA analyses, P-4-MPIMP–Cu was found to be higher stable than other synthesized polymer and polymer–metal complexes. While conductivity measurements of polymer and polymer–metal complexes were done by electrometer using four point probe techniques, electrochemical and optical band gap values of 4-MPIMP, P-4-MPIMP and polymer–metal complexes were determined by using cyclic voltammetry and UV–vis measurements. Conductivity and band gap values show that this polymer and polymer–metal complexes are a typical semiconductor.     

New fluorescent chemosensor based on quinoline and coumarine for Cu

A new fluorescent chemosensor based a coumarin fluorophore and an 8-hydroxyquinoline ionophore was synthesized and characterized by ¹H NMR, IR and ESI-HRMS. Its selectivity toward metal ions in acetonitrile (1% water, v/v) was investigated by UV absorption and fluorescence spectroscopy. The results showed that this chemosensor exhibited good selectivity toward Cu²⁺ over other metal ions by enhancement of fluorescence intensity more than 13-fold, and the fluorescent color change could be observed by naked eyes under the light of 365 nm. The absorption spectra of the sensor (L) toward the concentration of Cu²⁺ indicated the formation of L–Cu²⁺ complex, and the complex was 1:1 ratio according to Job plot experiment. Both of photo-induced electron transfer (PET) and intramolecular charge transfer (ICT) mechanisms were considered to be operational for fluorescence enhancement and spectral shift. The detection limit of Cu²⁺ was determined to be 1.16 μM, a satisfying level to detect Cu²⁺ in micromolar scale.     

Characteristics of nickel sulphide reduction in Ni2+ free background and Watts nickel plating electrolytes

Abstract

The electrochemical behaviour and composition of nickel sulphide coatings deposited on glassy carbon (GC) electrode by the successive ionic layer adsorption and reaction (SILAR) method using a nickel(II) ammonia complex and Na₂S solutions have been studied in Ni²⁺ free background, Watts nickel plating and 0·05 M H₂SO₄ electrolytes by the cyclic voltammetry and X-ray photoelectron spectroscopy (XPS) methods. Analysis of XPS data suggests that the coating is a mixture of two sulphides where NiS dominates. In the Ni²⁺ free background solution at first the electrochemical reduction of the sulphur rich nickel sulphide to NiS occurs. After that the NiS to metallic Ni is reduced in the potential range of H₂ evolution. During the cathodic reduction of the coating in Watts nickel plating electrolyte the sulphur is reduced in the potential range from 0·0 to ?0·4 V, while at the potential values <?0·5 V the sulphur rich nickel sulphide and NiS reduction in the H₂ evolution range and Ni plating occur.     

Sorption of Hg2+, Nd3+, Dy3+, and Uo 22+ ions at polysiloxane xerogels functionalized with phosphonic acid derivatives

The sorption properties of silicas with mono- and bifunctional surface layers containing the complexing fragment ≡Si(CH₂)₃NHP(S)(OC₂H₅)₂ were studied. It was found that xerogels synthesized by the solgel method (like mesoporous silicas obtained by the template method) can extract mercury(II) ions from acidified solutions (SSC up to 450 mg/g). In a nonporous xerogel with a bifunctional surface layer (≡P=S/-SH), thiol groups proved to be primary sorption sites for Hg²⁺ ions; part of the ligand groups were inaccessible to metal ions. Xerogels containing the phosphonic acid residues ≡Si(CH₂)₂P(O)(OH)₂ sorbed uranyl and lanthanide ions from their nitrate solutions. The resulting surface complexes contained two (for the UO₂²⁺ ion) or three innersphere ligand groups (for the Nd³⁺ and Dy³⁺ ions). The maximum SSCs were 340 mg/g for the uranyl ion and 120 mg/g for the lanthanide ions. Original Russian Text ? O.A. Dudarko, V.P. Goncharik, V.Ya. Semenii, Yu.L. Zub, 2008, published in Zashchita Metallov, 2008, Vol. 44, No. 2, pp. 207–212.     

Crystal growth and spectroscopic characterization of Yb-doped and Yb, Na-codoped PbF2 laser crystals

High-quality pure PbF₂, Yb:PbF₂ and Yb, Na:PbF₂ crystals are grown by the Bridgman method in a nonvacuum atmosphere. Room-temperature absorption, photoluminescence spectra, and fluorescence lifetimes belonging to the transitions between ground state ²F_7/2 and the excited state ²F_5/2 of Yb³⁺ ions in these crystals have been investigated. The influence of codoping with Na⁺ ions on the spectra has been studied. Experimental results show that codoping Na⁺ ions in different Na:Yb ratios can modulate the spectroscopy and photoluminescence properties of Yb³⁺ ions in a PbF₂ lattice in a large scope: the Na⁺ ions codoping with Yb³⁺ as charge compensators can suppress the deoxidization of Yb³⁺ to Yb²⁺, enhance the luminescence intensity and lengthen luminescence lifetime of Yb³⁺ ions.     

Sorption of Hg<Superscript>2+</Superscript>, Nd<Superscript>3+</Superscript>, Dy<Superscript>3+</Superscript>, and Uo<Stack><Subscript>2</Subscript><Superscript>2+</Superscript></Stack> ions at polysiloxane xerogels functionalized with phosphonic acid derivatives

The sorption properties of silicas with mono- and bifunctional surface layers containing the complexing fragment ≡Si(CH₂)₃NHP(S)(OC₂H₅)₂ were studied. It was found that xerogels synthesized by the solgel method (like mesoporous silicas obtained by the template method) can extract mercury(II) ions from acidified solutions (SSC up to 450 mg/g). In a nonporous xerogel with a bifunctional surface layer (≡P=S/-SH), thiol groups proved to be primary sorption sites for Hg²⁺ ions; part of the ligand groups were inaccessible to metal ions. Xerogels containing the phosphonic acid residues ≡Si(CH₂)₂P(O)(OH)₂ sorbed uranyl and lanthanide ions from their nitrate solutions. The resulting surface complexes contained two (for the UO ₂ ²⁺ ion) or three innersphere ligand groups (for the Nd³⁺ and Dy³⁺ ions). The maximum SSCs were 340 mg/g for the uranyl ion and 120 mg/g for the lanthanide ions.     

Influence of bath concentration and pH on electrodeposition process of ternary Zn-Ni-Mo alloy coatings

The influence of bath pH and also citrate and molybdate concentration, on the electrodeposition process of ternary Zn-Ni-Mo alloy coatings has been examined. The occurrence of the particular forms of the metal-citrate complexes in the electrolytes was analysed using UV-VIS spectroscopy and on the basis of the stability constants of the complexes. In the solutions with lower pH (4·5 and 5·7), in which free metal ions and ZnHCit^? and NiHCit^? complexes predominate, anomalous codeposition of nickel with zinc took place. In electrolytes with higher pH, containing excess of citrate, in which all the metal ions occur in the form of citrate complexes, and about 20% of the Zn²⁺ and Ni²⁺ ions form a ZnNiCit₂^4? mixed complex, the codeposition changes from anomalous to normal. The percentage of Mo in the alloy increases with the increase in concentration of uncomplexed MoO₄^2? ions in the solution. Alloys with much higher Mo content may be obtained from the bath in which preferential deposition of nickel (normal codeposition) takes place.     

Preparation,characterization, electrochemistry and in situ spectroelectrochemistry of novel α-tetra[7-oxo-3-(2-chloro-4-fluorophenyl)coumarin]-substituted metal-free,cobalt and zinc phthalocyanines

In this study, a novel ligand, 7-(2,3-dicyanophenoxy)-3-(2-chloro-4-fluorophenyl)coumarin was synthesized by the reaction of 3-(2-chloro-4-fluorophenyl)-7-hydroxycoumarin with 1,2-dicyano-3-nitrobenzen in dry DMF as the solvent in the presence of K₂CO₃ as the base. The preparation of the corresponding phthalocyanines H₂Pc, CoPc and ZnPc, substituted with 7-oxo-3-(2-chloro-4-fluorophenyl)coumarin functional groups at α positions of the Pc ring, was achieved by the cyclotetramerization of the coumarin ligand without any metal salts or with the relevant metal(II) acetates in 2-N,N-dimethylaminoethanol. The structures of the compounds were confirmed by elemental analysis, UV–vis, IR, MALDI-TOF mass and ¹H NMR spectra. In addition, aggregation and redox properties of the novel phthalocyanines with four halogenated coumarinoxy substituents at α positions of the phthalocyanine ring were compared with those of previously reported corresponding ones with β-substitution, by UV–vis spectroscopy, in situ spectroelectrochemistry and voltammetry. Remarkable differences in these properties between α- and β-substituted compounds were detected, and discussed in detail.     

Synthesis and conductivities of (μ-cyano)phthalocyaninatometal compounds

A review of the synthesis and characterization of a new type of stacked, bridged macrocyclic metal complexes, the (μ-cyano)phthalocyaninatometal compounds [PcMCN]_n (2) is given. By using the routes described in Fig. 3 the polymers were synthesized with M = Co³⁺, Fe²⁺, Fe³⁺, Mn³⁺ and Cr³⁺ as the central metal ion. The compounds were characterized by IR, far-IR, UV, thermal and elemental analysis, and partly by ¹H NMR and FD (field desorption) mass spectroscopy.[PcCoCN] (2a) and [PcFeCN]_n (2b) exhibit d.c. room temperature conductivities around 10^?2 S/cm without doping, thereby showing conductivities which are in the same range as the iodine-doped phthalocyaninatosiloxanes [PcSiO]_n.     

Preparation and luminescent characteristics of Sr3RE2(BO3)4:Dy (RE = Y, La, Gd) phosphors for white LED

Dysprosium-activated Sr₃RE₂(BO₃)₄ (RE = Y, La, Gd) phosphors were synthesized by a high temperature solid-state reaction method. The phase uniformity of the phosphors was characterized by X-ray powder diffraction (XRD) and the luminescence characteristics were investigated. The excitation spectra at 575 nm emission show strong spectral bands in the region of 300-500 nm. The emission spectra of the phosphors with 365 nm excitation show three bands centered at 484 nm, 575 nm and 680 nm, which originate from the transitions of ⁴F_9/2 → ⁶H_15/2, ⁴F_9/2 → ⁶H_13/2 and ⁴F_9/2 → ⁶H_11/2 of Dy³⁺, respectively. The effect of Dy³⁺ concentration on the emission intensity of the phosphors was investigated. The fluorescence decay curves for ⁴F_9/2 → ⁶H_13/2 excited at 365 nm and monitored at λ_em of 575 nm were measured. The decay times decreased slowly with increasing Dy³⁺ doping concentration due to a trap capturing to resonance fluorescence transfer of the activated ions and due to the exchange interactions between activated ion pairs. In order to determine the type of interaction between activated ions, the concentration dependence curves (lg(I/x) versus lg x) of Sr₃RE₂(BO₃)₄:Dy³⁺ (RE = Y, La, Gd) were plotted. The concentration quenching mechanism of the ⁴F_9/2 → ⁶H_13/2 (575 nm) transition of Dy³⁺ is the d-d interaction. All results indicate these phosphors are promising white-color luminescent materials.     

Color-tunable and white-light emitting lanthanide complexes based on (CexEuyTb1−x−y)2(BDC)3(H2O)4

Ce³⁺, Eu³⁺ and Tb³⁺ complexes were synthesized through facile and mild approaches with terephthalic acid (H₂BDC) as the ligand. Their chemical compositions were determined as (Ce_xEu_yTb_1−x−y)₂(BDC)₃(H₂O)₄ by elemental analysis (EA), Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) measurements. Fluorescent properties of the as-synthesized complexes were investigated by changing the molar ratio of Ce³⁺, Tb³⁺ and Eu³⁺ ions, and the optimized ratio of 3.0:2.0:0.15 for Ce³⁺:Tb³⁺:Eu³⁺ in the complex was determined for white-light emission. Tuning on the emitting color was realized by adjusting the ratio among lanthanide ions, indicating the energy transfer process inside the complex. It was found that Tb³⁺ could sensitize the fluorescence of Eu³⁺ while its own fluorescence was quenched by the latter ion, and concentration quenching of Ce³⁺ was also observed. Fairly good thermal stability and oxidation resistance of the as-synthesized complexes were also demonstrated.     

Concentration-dependent luminescence and energy transfer of flower-like Y2(MoO4)3:Dy phosphor

Flower-like Y₂(MoO₄)₃:Dy³⁺ phosphors have been synthesized via a co-precipitation approach with the aid of β-cyclodextrin. The crystal structure and morphology of the phosphors were characterized by XRD (X-ray diffraction) and FE-SEM (field emission scanning electron microscopy), respectively. The excitation and emission properties of the phosphors were examined by fluorescence spectroscopy. The dependence of color coordinates on the Dy³⁺ doping concentration was analyzed. The energy transfer mechanism between Dy³⁺ ions was studied based on the Huang's theory, I-H and Van Uitert's models. It was concluded simultaneously from these three routes that the electric dipole-dipole interaction between Dy³⁺ ions is the main physical mechanism for the energy transfers between Dy³⁺.     

Adsorption properties of Ag（Ⅰ）, Au（Ⅲ）, Pd（Ⅱ） and Pt（Ⅳ） ions on commercial 717 anion-exchange resin

The adsorption properties of the four precious metal ions (Ag(I), Au(II), Pd(III) and Pt(IV)) on the commercial Cl^?-form 717 strongly basic anion-exchange resin were studied in detail. The effects of the contact time, solution acidity, and concentrations of Cl^? and Pb²⁺ ions on the adsorption properties were studied by the batch method. Then, the column method was conducted under the optimized adsorption conditions (pH=3.0). The effects of the sample loading flow rate and the length-to-diameter ratios of the columns were investigated. The precious metal ions adsorbed could not be eluted completely after the saturated adsorption because the precious metal ions were found to be reduced to their metallic states during the adsorption process. So, it is recommended that the commercial Cl^?-form 717 strongly basic anion-exchange resin should be decomposed directly to recovery the precious metals after the saturated adsorption.     

Partial oxidation of methane over bimetallic nickel–lanthanide oxides

The study of partial oxidation of methane (POM) over bimetallic nickel–lanthanide oxides was undertaken. Binary intermetallic compounds of the type LnNi (Ln = Pr, Gd, Lu) were used as bimetallic nickel–lanthanide oxides precursors and the products (NiO·Pr₂NiO₄, 2NiO·Gd₂O₃ and 2NiO·Lu₂O₃) were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy, Raman and temperature programmed reduction. The catalytic activity increases when gadolinium or lutetium replaces praseodymium and the selectivity of the bimetallic nickel–lanthanide oxides is clearly different from that of single metal oxides and/or mechanical mixtures.The existence of an unusual synergism effect between the two metal oxide phases (NiO and Ln₂O₃) that lead to higher conversions of methane and higher selectivities to hydrogen and carbon monoxide correlate also the catalysts stability to deactivation. The activity and selectivity of the gadolinium and lutetium compounds is, under the same conditions, equivalent to that of a platinum commercial catalyst, 5 wt% Pt/Al₂O₃, which stresses the good catalytic performance of this new type of compounds for the production of H₂ and CO (H₂/CO = 2).     

Inhibitory effects of manganeous,cadmium and zinc ions on hydrogen evolution reaction and corrosion of iron in sulphuric acid solutions

The presence of metal ions (Cd²⁺, Mn²⁺, Zn²⁺), more electronegative than the cathodic potential for the hydrogen evolution reaction on iron in a 0.25M H₂SO₄ solution, inhibits the hydrogen evolution reaction and corrosion of iron. This effect has been explained as the under-potential deposition of the adatoms of these metals on iron.     

Synthesis,luminescent properties,and theoretical study of novel Sm~(3+) and Dy~(3+) complexes containing β-diketone and 1,10-phenanthroline

Two new ternary complexes of 1-(2-thienyl)-3-(p-phenylethynylphenyl)-1,3-propanedione (HTPP) and 1,10-phenanthroline (phen) with Sm³⁺ and Dy³⁺ were synthesized. The composition of the ternary complexes was characterized as Sm(TPP)₃phen and Dy(TPP)₃phen, respectively, by infrared (IR) spectra, chemical analysis, elemental analysis, and thermodynamic analysis. At room temperature, under UV light excitation, the Sm³⁺ and Dy³⁺ complexes exhibit characteristic emissions of the central ions. It is found that the fluorescence intensity of Sm(TPP)₃phen is stronger than that of Dy(TPP)₃phen. In order to explain this phenomenon, an accurate quantum chemistry calculation was carried out, and the result is in good agreement with the experiment data.     

The early stages of oxidation of ion-implanted nickel at high temperature

The early stages of oxidation of nickel implanted with nickel, chromium, or lithium ions in oxygen at 1100°C have been studied using various electron-optical techniques. The unimplanted metal develops initially a fine-grained, convoluted scale having a ridged, cellular structure. Subsequently, the oxide grains increase in size significantly and oxidation becomes predominantly controlled by diffusion of Ni ²⁺ ions across a compact, columnar scale. Implantation of the surface with nickel ions has no significant effect on the initial oxidation behavior. However, after implantation with chromium or lithium ions, the development of the NiO scale is, in the early stages of oxidation, suppressed by formation of NiCr ₂O₄ or LiO₂ nodules, respectively. Subsequently, the implanted species are incorporated into the steady-state NiO scale where they dope the oxide and thus influence the diffusion rate of Ni ²⁺ ions through it. As would be predicted, the steady-state oxidation rate of chromium-implanted nickel is increased while that of lithium-implanted nickel is decreased compared with that of the unimplanted metal.