Study of Complex Formation between Kryptofix 21 with La<Superscript>3+</Superscript>, Y<Superscript>3+</Superscript> and Ce<Superscript>3+</Superscript> Cations in Some Binary Mixed Non-Aqueous Solvents Using the Conductometric Method

The complexation reactions between La³⁺, Y³⁺ and Ce³⁺ cations with the macrocyclic ligand, kryptofix 21, were studied in methanol-acetonitrile (MeOH-AN) and methanol-methylacetate (MeOHMeOAc) binary mixed solvent solutions at different temperatures using the conductometric method. The conductance data show that in most solvent systems, the kryptofix 21 forms a 1: 1 [M: L] complex with La³⁺, Y³⁺ and Ce³⁺ metal cations, but in the case of Y³⁺ cation in pure methylacetate, in addition of formation of a 1: 1 [ML] complex, 1: 2 [ML₂] and 1: 3 [ML₃] complexes are formed in solution. In the case of Ce³⁺cation, a 1: 1 [ML] and also a 1: 2 [ML₂] complexes are formed in this solvent system at all studied temperatures. The electrical conductance data in acetonitrile, show that a 1: 1 [ML] and also a 1: 2 [ML₂] complexes are formed between the ligand and La³⁺ and Ce³⁺ metal cations at different temperatures. The stability constants of the 1: 1 [ML] complexes were determined using the conductometric data and a computer program, GENPLOT. A non-monotonic relationship was observed between log_{K f} of the 1: 1 complexes with the composition of the binary solvent solutions which was discussed in term of solvent-solvent interactions and also preferential solvation of the metal cations and the ligand in solutions. The selectivity order of the ligand for the metal cations in MeOH–AN and MeOH–MeOAc binary solvent solutions, at 25°C was found to be: Y³⁺ > La³⁺ > Ce³⁺ and La³⁺ > Y³⁺ > Ce³⁺, respectively. The values of the standard thermodynamic quantities (ΔH _c ^° and ΔS _c ^° ) for formation of the 1: 1 complexes were obtained from temperature dependence of the stability constans of the complexes and the results show that the thermodynamics of the complexation reactions between kryptofix 21 and La³⁺, Y³⁺ and Ce³⁺ cations, is affected by the nature and composition of the mixed solvents systems.     

Effect of the Electrode Material on the Reduction of La<Superscript>3+</Superscript> and Ce<Superscript>3+</Superscript> in Fluoride-Conducting Solid Electrolytes

The reduction of immobile cations La³⁺ and Ce³⁺ in fluoride-conducting solid electrolytes (FSE) LaF₃ (Eu²⁺ 0.8 mol %), LaF₃ (Sr²⁺ 5 mol %), and CeF₃ (Sr²⁺ 5 mol %) in contact with Ag, Bi, Si, La, Ce, and Sm working electrodes is studied by chronoamperometry and voltammetry with linear potential scan. Discovered is linear dependence of initial segments of potentiostatic transients of cathodic current on t ^1/2 at FSE interfaces with Ag, Bi, La, Ce, and Sm. The dependence is due to diffusion-controlled instantaneous nucleation of Ln and Ce. The La³⁺ and Ce³⁺ reduction at the FSE/Ag interface is reversible in a narrow region. The reduction and oxidation of La³⁺ and Ce³⁺ (cations of the FSE rigid lattice) at the FSE/Me (Me = La, Ce and Sm, Bi, Si) interface is irreversible and involves a chemical reaction.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 662–672.Original Russian Text Copyright © 2005 by Turaeva, Kot, Urchukova, Murin.     

Incorporation of Mg<Superscript>2+</Superscript>, Sr<Superscript>2+</Superscript>, Ba<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> into aragonite and comparison with calcite

We have investigated the presence of foreign ions into the bulk structure and the external surfaces of aragonite using periodic ab-initio methods. Four cations isovalent to Ca²⁺ were studied: Mg²⁺, Sr²⁺, Ba²⁺ and Zn²⁺. The calculations were performed at structures (bulk, surface) that contain four and eight CaCO₃ units. Our results, at the Hartree-Fock level, show that the incorporation of those ions into aragonite depends strongly on their size. Mg²⁺ and Zn²⁺, due to their smaller size, can substitute Ca²⁺ ions in the crystal lattice while the incorporation of Sr²⁺ and Ba²⁺ into aragonite is energetically less favoured. Examination of the [011], [110] and [001] surfaces of aragonite revealed that the surface incorporation reduces the energetic cost for the larger ions. These systems provide challenging examples for most shape analysis methods applied in Mathematical Chemistry.     

Thermodynamic behavior of complexation of 18-crown-6 with Tl<Superscript>+</Superscript>, Pb<Superscript>2+</Superscript>, Hg<Superscript>2+</Superscript>, and Zn<Superscript>2+</Superscript> metal cations in methanol-water binary media

The equilibrium constants and thermodynamic parameters for complex formation of 18-Crown-6 (18C6) with Tl⁺, Pb²⁺, Hg²⁺, and Zn²⁺ metal cations have been determined by conductivity measurements in methanol (MeOH)-water (H₂O) binary solutions. 18-Crown-6 forms 1:1 complexes with Hg²⁺ and Zn²⁺ cations, but in the case of Tl⁺ and Pb²⁺ cations, in addition to 1:1 stoichiometry, 1:2 (ML₂) complexes are formed in some binary solvents. The thermodynamic parameters (ΔH _c⁰ and ΔS _c⁰), which were obtained from the temperature dependences of equilibrium constants, show that in most cases the complexes are enthalpy destabilized but entropy stabilized. Non-linear behavior is observed between the equilibrium constants (log K _f ) of complexes and the composition of the mixed solvent. The selectivity of the ligand for these metal cations is sensitive to the solvent composition, and, in some cases, the selectivity order is reversed in certain compositions of the mixed solvent. The results also show that the mechanism of complexation reactions and the stoichiometry of complexes of some metal cations change with the nature and even with the composition of the mixed solvent. The article was submitted by the authors in English.     

Sorption of Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> by Natural Biomaterial: Duck Feather

Feather fibers were modified by treatment with 5% tannic acid (TA) solution. Kinetics of the modification was investigated as a function of the reaction time. The maximum loading of TA on feather reached 8.3% after being treated by TA for 9 h. The adsorption of metal cations (Cu²⁺, Zn²⁺) by unmodified and TA-modified feather fibers was investigated as a function of fiber weight gain, temperature, and pH of the metal solution. The adsorption was enhanced at alkaline pH and ambient temperature and increased with the weight gain of TA. The maximum uptake of metal cations (Cu²⁺, 0.77 mmol/g; Zn²⁺, 0.95 mmol/g) was obtained by TA-modified feather at weight gain: 8.3%, pH 11, while at the acidic pH, the adsorption of metal cations by either unmodified or TA-modified feather was negligible. The influence of anions on the adsorption of metal cations was also studied. The uptake of Cu²⁺ from chloride was higher and faster than that from nitrate. Desorption of the metals was performed at acidic pH 2.5 for 48 h. The feather–TA–metal complexes exhibited higher stability for metal cations than the feather–metal complexes. All these experiments reveal that TA-modified feather fibers have good adsorption to metal cations and can be used as metal adsorbent in wastewater treatment.     

Selective extraction of Fe<Superscript>3+</Superscript> ions from Fe<Superscript>3+</Superscript>-Zn<Superscript>2+</Superscript> mixture with phosphate sorbents

The absorption of Fe³⁺ ions from Fe³⁺-Zn²⁺ mixture with zinc and calcium phosphates was studied.     

Sorption of Cs<Superscript>+</Superscript> and Sr<Superscript>2+</Superscript> by ion exchanger based on titanium phosphate

Sorption capacity of a composite ion exchanger based on titanium phosphate for Cs⁺ and Sr²⁺ cations was studied. The effect of pH and concentration of salts and, in particular, sodium chloride in solution on the sorption efficiency and distribution coefficient was analyzed. The diffusion coefficients were calculated for the Cs⁺ and Sr²⁺ cations and the time of half-exchange of the Na⁺ cation for the Cs⁺ and Sr²⁺ cations was found.     

Synthesis of Y-type zeolites with high degree of Na<Superscript>+</Superscript> cation exchange for La<Superscript>3+</Superscript>

Effect of parameters of the ion exchange of Na⁺ cations for La³⁺ in Y zeolites with SiO₂/Al₂O₃ molar ratios of 5.1 and 6.0 on the degree of exchange and physicochemical properties of the resulting LaNaY samples was studied. The conditions in which deeply substituted La-forms of a Y zeolite with high degree of crystallinity can be obtained were determined.     

Photoluminescence in Er<Superscript>3+</Superscript>/Yb<Superscript>3+</Superscript>-doped silica-titania inverse opal structures

Er³⁺ photoluminescence (PL) and Yb³⁺ → Er³⁺ energy transfer (ET) phenomena in the near infrared (NIR) have been studied in three-dimensional (3-D) inverse opal (IO) structures synthesized by a colloidal/sol–gel route, starting with the deposition of polystyrene microsphere (235 nm and 460 nm diameter) direct opal templates by convective self-assembly, followed by infiltration of the interstices with Er³⁺/Yb³⁺-doped silica, titania and silica-titania sols and heat-removal of the polymeric template material. The crystalline quality of the IOs has been optimized through suitable substrate treatments, plus the control of temperature and humidity during deposition of the templates. The structural and optical properties of the 3-D opal and IO structures have been studied by field emission scanning electron microscopy and visible-NIR reflection spectroscopy, in order to assess the relationship between microstructure and the photonic properties obtained. Photonic bandgaps have been evidenced by the corresponding stop bands in the reflection spectra. The shape and the intensity of the Er^{3+ 4}I_13/2 → ⁴I_15/2 transition at ~1.5 μm were modified in most IOs relatively to similar matrix deposits without a photonic crystal structure, particularly in the case of pure silica and titania IOs, where the PL peak narrowed and intensified. It was not possible at this stage to detect Yb³⁺ → Er³⁺ ET phenomena in the IOs structures.     

Cation binding by 2<Superscript>1</Superscript>,3<Superscript>1</Superscript>-diphenyl-l <Superscript>2</Superscript>,4<Superscript>2</Superscript>-dioxo-7,10,13-trioxa-1,4(3,1)-diquinoxalina-2 (2,3),3(3,2)-diindolizinacyclopentadecaphane and its acyclic analog

The binding of cations Li⁺, Na⁺, K⁺, Cs⁺, Ag⁺, Zn²⁺, Ni²⁺, Co²⁺, NH₄ ⁺ (group I), H⁺, Mg²⁺, Al³⁺, Ga³⁺ (group II), and Ca²⁺, Pb²⁺ (group III) by 2¹,3¹-diphenyl-l ²,4²-dioxo- 7,10,13-trioxa-l,4(3,1)-diquinoxalina-2(2,3),3(3,2)-diindolizinacyclopentadecaphane (1), which contains two indolizine and two quinoxaline fragments and 3,6,9-trioxaundecanes spacer, and by its acyclic analog (2) was studied using cyclic voltammetry in MeCN/0.1 M Bu₄NBF₄. It was concluded that the ions of group I are not bound by these compounds, the ions of group II exhibit the reversible redox-switched binding by the carbamoyl groups of the quinoxaline fragments, whereas the ions of group III are bound not only by the initial compounds and radical cations 1 and 2, but also by dication 1. This binding of the Ca²⁺ and Pb²⁺ ions stabilizes dication 1.     

Niobium(V) oxide doped with Mg<Superscript>2+</Superscript> and Gd<Superscript>3+</Superscript> cations: Synthesis and structural studies

Methods for direct doping of niobium pentoxide with photovoltaically inactive Mg²⁺ and Gd³⁺ cations were developed for subsequent use in the synthesis of a stock for growing single crystals of lithium niobate with improved optical characteristics. The Raman spectra of doped pentoxides Nb₂O₅: Mg and Nb₂O₅: Gd revealed their island structures.     

Near-infrared quantum cutting in Tb<Superscript>3+</Superscript> and Yb<Superscript>3+</Superscript>-doped Y<Subscript>2</Subscript>O<Subscript>3</Subscript> nanophosphors

Properties of the quantum-cutting phosphors are dependent on various factors such as dopant concentration, crystallinity, homogeneity, particle size and surface morphology. Effective control of the above parameters can enhance the quantum-cutting ability of the phosphor material. Nano-sized particles of Y₂O₃:Tb³⁺,Yb³⁺ were prepared with a solution-based co-precipitation method and subsequent calcination. Effective control of the reaction parameters and doping concentration helped to produce uniform nanostructures with high quantum-cutting efficiency up to 181.1 %. The energy transfer mechanism between Tb³⁺ and Yb³⁺ was studied by considering their spectroscopic properties and time-resolved spectroscopy. The high efficiency and small particle size of the quantum-cutting phosphor Y₂O₃:Tb³⁺,Yb³⁺ make it a suitable candidate for its application in solar cells.     

Effect of Ca<Superscript>2+</Superscript>, Mg<Superscript>2+</Superscript>, Fe<Superscript>3+</Superscript>, and Al<Superscript>3+</Superscript> Ions on the Deposition of Electrolytic Manganese Dioxide from Chloride Solutions

The effect of Ca²⁺, Mg²⁺, Fe³⁺, and Al³⁺ ions on the deposition of electrolytic manganese dioxide from chloride solutions was studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 5, 2005, pp. 751–754.Original Russian Text Copyright © 2005 by Kolosnitsyn, Minnikhanova, Karaseva, Dmitriev, Muratov.     

1,9-Dicarbonyl-2,8-dioxo-butyne-ester Ferrocenophane: Synthesis,Structure and Recognition Properties for Co<Superscript>2+</Superscript> and Cu<Superscript>2+</Superscript> Ions

An efficient highly diluted synthetic approach to the synthesis of 1,9-dicarbonyl-2,8-dioxo-butyne ester ferrocenophane (L) has been developed. The title compound was characterized by IR, UV, FL, 1H NMR, spectroscopies, elemental analysis and so on. Further complex L shows fluorescence responses to Co²⁺ and Cu²⁺ in CH3OH, The results indicate that the complex could be applied in multianayte detection. The binding ability of receptor L CH3OH was tested for various cations (Co²⁺, Cu²⁺, Zn²⁺, and Ni²⁺ in water) and the binding constants for Co²⁺ and Cu²⁺ were the computed, having a distinct absorbance shift. The receptor is a very attractive array because its distinct absorbance shift profile in a semi-aqueous phase, making it applicable in the area of biology, environmental sciences and material chemistry.     

Hydrothermal synthesis of core-shell structured PS@GdPO<Subscript>4</Subscript>:Tb<Superscript>3+</Superscript>/Ce<Superscript>3+</Superscript> spherical particles and their luminescence properties

Non-aggregated spherical polystyrene (PS) particles were coated with GdPO₄:Tb³⁺/Ce³⁺ phosphor layers by a conventional hydrothermal synthesis using poly(vinylpyrrolidone) (PVP) as an additive without further annealing treatment. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence (PL), as well as luminescence decay experiments were used to characterise the resulting core-shell structured PS@GdPO₄:Tb³⁺/Ce³⁺ samples. The results of XRD indicated that the PS particles were successfully coated with the GdPO₄:Tb³⁺/Ce³⁺ phosphor layers, which could be further verified by the images of FESEM. Under ultraviolet excitation, the PS@GdPO₄:Tb³⁺/Ce³⁺ phosphors show Tb³⁺ characteristic emission, i.e. ⁵D₄-⁷F_J (J = {6, 5, 4, 3}) emission lines with green emission ⁵D₄-⁷F₅ (543 nm) as the most prominent group. The core-shell phosphors so obtained have potential applications in field emission display (FED) and plasma display panels (PDP).     

Extraction of metal ions (Fe<Superscript>3+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript>) using immobilized-polysiloxane iminobis(n-2-aminophenylacetamide) ligand system

A new insoluble solid functionalized ligand system bearing chelating ligand group of the general formula P-(CH₂)₃-N[CH₂CONH(C₆H₄)NH₂]₂, where P represents [Si–O] _n polysiloxane network, was prepared by the reaction of the immobilized diethyliminodiacetate polysiloxane ligand system, P-(CH₂)₃N(CH₂CO₂Et)₂ with 1,2-diaminobenzene in toluene. ¹³C CP-MAS NMR, XPS and FTIR results showed that most ethylacetate groups (–COOEt) were converted into the amide groups (–N–C=O). The new functionalized ligand system exhibits high capacity for extraction and removal of the metal ions (Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) with efficiency of 95–97% after recovery from its primary metal complexes. This functionalized ligand system formed 1:1 metal to ligand complexes.     

Hydrolytic Behavior of La<Superscript>3+</Superscript> and Sm<Superscript>3+</Superscript> at Various Temperatures

The hydrolytic species of lanthanide ions, La³⁺ and Sm³⁺, in water at I = 0.1 mol·dm^?3 KCl ionic strength and temperatures of 298.15, 310.15 and 318.15 K were investigated by potentiometry. The hydrolytic species were modeled by the HySS simulation program. From the results, the hydrolytic species of each metal ion at different temperatures were calculated using the program HYPERQUAD2013. The hydrolysis constants (log₁₀ β) of [La(OH)]²⁺ and La(OH)₃ were calculated as ?8.52 ± 0.46, ?26.84 ± 0.48, and log₁₀ β values of [Sm(OH)]²⁺, [Sm(OH)₂]⁺, Sm(OH)₃ were calculated as ?7.11 ± 0.21, ?15.84 ± 0.25 and ?23.44 ± 0.52 in aqueous media at 298.15 K, respectively. The dependence of the hydrolysis constants on the temperature allowed us to calculate the enthalpy, entropy, and Gibbs energy of hydrolysis values of each species.     

Formation of coordination compounds with aniline in the interlayer space of Ca<Superscript>2+</Superscript>-, Cu<Superscript>2+</Superscript>- and Fe<Superscript>3+</Superscript>-exchanged montmorillonite

The influence of Ca²⁺-, Cu²⁺- and Fe³⁺-exchanged montmorillonite (MMT) on the type of interaction with aniline in the interlayer space of MMT has been studied by means of X-ray powder diffraction and infrared spectra. Results of X-ray diffraction showed that aniline was successfully intercalated into the interlayer space of MMT. Based on IR spectra evaluation, aniline was indirectly coordinated through a water-bridge in Ca²⁺- and Fe³⁺-MMT and it was indirectly coordinated through a water-bridge as well as protonated in Cu²⁺-MMT (the spectrum of protonated aniline showed deformation and changes in the NH ₃ ⁺ absorption at approximately 1521 cm^?1). It is important to point out that Cu²⁺-MMT indirect coordination and protonation occur simultaneously.     

The New Fluorescence Enhancement System Eu<Superscript>3+</Superscript>-ARADE-HMTM-Al<Superscript>3+</Superscript> and its Analytical Application

A new bis-Schiff base ligand, N,N-bis-(4-N-aminothiourea-2-amylidene)-4,4-diaminodiphenyl ether (ARADE), was synthesized. Its complex with Eu³⁺ in DMF emits the intrinsic fluorescence of Eu³⁺. The fluorescence intensity of the Eu³⁺-ARADE system was enhanced about 60-fold by the addition of hexamethylene tetramine (HMTM) and potash alum. This is a new fluorescence enhancement phenomenon. The excitation and emission wavelengths are 375nm and 615nm, respectively. Under optimal conditions, the fluorescence intensities vary linearly with the concentration of Eu³⁺ in the range of 7.8×10^–9–1.75×10^–5mol·L^–1 with a detection limit of 5.2×10^–9mol·L^–1, or with the concentration of Al³⁺ in the range of 3.1×10^–7–9.7×10^–5mol·L^–1 with a detection limit of 2.7×10^–7mol·L^–1. The interferences of some rare earth metals and other inorganic ions were described. This method was applied to the determination of Eu³⁺ in high purity yttrium oxide and the analysis of Al³⁺ in alloy steel standard samples. The mechanism of fluorescence enhancement was also studied.     

Scalar-relativistic 5f-in-core pseudopotentials and core-polarization potentials for trivalent actinides: calibration calculations for Ac<Superscript>3+</Superscript>, Cm<Superscript>3+</Superscript> and Lr<Superscript>3+</Superscript> complexes

The performance of recently proposed 5f-in-core pseudopotentials for the trivalent actinides was investigated in calculations for model complexes An³⁺L ⁿ⁻ for three selected actinides (An³⁺ = Ac³⁺, Cm³⁺, Lr³⁺) and eight simple ligands with atoms from the first three periods of the table of elements (L ⁿ⁻ = F⁻, Cl⁻, OH⁻, SH⁻, CO, NH₂⁻, H₂O, H₂S, NH₃). Results of Hartree-Fock and Coupled Cluster with singles, doubles and perturbative triples calculations using basis sets of quadruple-zeta quality are compared to corresponding reference data obtained with scalar-relativistic energy-adjusted 5f-in-valence small-core pseudopotentials. The inclusion of core-polarization potentials in the 5f-in-core pseudopotential calculations and corrections of the basis set superposition error by the counterpoise correction leads to very good agreement between the 5f-in-valence and 5f-in-core pseudopotential results for bond lengths, bond angles and binding energies. Results from 5f-in-core pseudopotential calculations using different density functionals also show reasonable agreement with the more rigorous Coupled Cluster results. It is argued that the An 5f rather than the An f population is a useful criterion for the applicability of a specific An 5f-in-core pseudopotential.