Thorium(IV) and neptunium(V) uptake from carbonate containing aqueous solutions by HDTMA-modified natural zeolites

The ²³²Th-uptake ([Th(IV)]° = 9.7 × 10^?5 M) from carbonate solutions ([CO ₃ ² ]_tot = 0.25 M, 9.0 < pH_c < 10.8) by raw and HDTMA-modified HEU-type zeolitic-, chabazitic- and phillipsitic-tuffs was investigated. The strong uptake by the HDTMA-tuffs at pH_c≈9 was assigned to the Th(CO₃) ₅ ^6? and ThOH(CO₃) ₄ ^5? predominance. The sorption coefficients (R _d) decreased with increasing pH_c indicating carbonate competition. Enhanced R _d values for pH_c > 10.5 are likely due to ThO₂(am)-precipitation. The ²³⁷Np-uptake ([Np(V)]° = 2.6 × 10^?5 M) from carbonate solutions ([CO ₃ ² ]_tot = 0.25 and 3.0 × 10^?4 M) by raw and HDTMA-modified HEU-type zeolitic tuff and pulverized pure heulandite crystals was studied under Ar-atmosphere at 6 < pH_c < 11. The R _d values for both elements indicated the modified tuffs potential to remove tetravalent- and pentavalent actinides from environmental matrices.     

Interaction of elemental mercury with selenium surfaces: model experiments for investigations of superheavy elements copernicium and flerovium

The adsorption behavior of ¹⁹⁷Hg and ^183–185Hg on red amorphous selenium (red a-Se) and trigonal selenium (t-Se) was investigated experimentally by off-line and on-line gas chromatographic methods, in preparation of a sensitive chemical separation and characterization of the transactinides copernicium (Cn, Z = 112) and flerovium (Fl, Z = 114). Monte-Carlo simulations of a diffusion controlled deposition were in good agreement with the experimental results, assuming as interaction limits ?ΔH _ads ^red a-Se (Hg) > 85 kJ/mol, and ?ΔH _ads ^t-Se (Hg) < 60 kJ/mol. Both Se allotropes can be used as stationary surfaces in comparative gas-chromatographic chemical investigations of Cn and Fl.     

Mechanism of the oxidation of hydrazoic acid by tetrachloroaurate(III) ion

The oxidation of hydrazoic acid in perchloric acid in the absence of added chloride under pseudo first-order conditions ([HN₃] » [AuCl ₄ ^? ]) is first order in [Au(III)]. Michaelis–Menten type of dependence (linear plots of k _obs ^?1 vs [HN₃]^?1) is observed with respect to [HN₃]. The k _obs is independent of ionic strength and the plot between k _obs ^?1 and [H⁺] is linear. The inner-sphere mechanism is consistent with the formation of an axial complex (K = 25 dm³ mol^?1) between AuCl₃(HO)^? ion and HN₃ prior to its rate determining decomposition (k = 0.0182 s^?1). It is inferred that the free radicals N ₃ ^? do not oxidise Au(II). The reaction becomes outer-sphere in the presence of added Cl^? ions which are inferred to form a cage around the hydronium ion surrounding the AuCl ₄ ^? ions. The penetration of N ₃ ^? through the cage is rate controlling and within the cage, the electron transfer from N ₃ ^? ion to AuCl ₄ ^? is fast. The value of the rate determining constant k ₂ is 0.547 dm³ mol^?1 s^?1 and the equilibrium constant K _Cl for the cage formation is 5 dm³ mol^?1 at 25 °C. It is calculated that the minimum HN₃ concentration required before the reaction exhibits zero-order dependence in HN₃ is 0.31 mol dm^?3 when [H⁺] = 0.18 mol dm^?3 at 25 °C.     

Molecular structure and conformation of nitrobenzene reinvestigated by combined analysis of gas-phase electron diffraction,rotational constants,and theoretical calculations

The molecular structure and conformation of nitrobenzene has been reinvestigated by gas-phase electron diffraction (GED), combined analysis of GED and microwave (MW) spectroscopic data, and quantum chemical calculations. The equilibrium r _e structure of nitrobenzene was determined by a joint analysis of the GED data and rotational constants taken from the literature. The necessary anharmonic vibrational corrections to the internuclear distances (r _e ? r _a) and to rotational constants (B _e ⁽ⁱ⁾  ? B ₀ ⁽ⁱ⁾ ) were calculated from the B3LYP/cc-pVTZ quadratic and cubic force fields. A combined analysis of GED and MW data led to following structural parameters (r _e) of planar nitrobenzene (the total estimated uncertainties are in parentheses): r(C–C)_av = 1.391(3) Å, r(C–N) = 1.468(4) Å, r(N–O) = 1.223(2) Å, r(C–H)_av = 1.071(3) Å, \({\angle}\)C2–C1–C6 = 123.5(6)°, \({\angle}\)C1–C2–C3 = 117.8(3)°, \({\angle}\)C2–C3–C4 = 120.3(3)°, \({\angle}\)C3–C4–C5 = 120.5(6)°, \({\angle}\)C–C–N = 118.2(3)°, \({\angle}\)C–N–O = 117.9(2)°, \({\angle}\)O–N–O = 124.2(4)°, \({\angle}\)(C–C–H)_av = 120.6(20)°. These structural parameters reproduce the experimental B ₀ ⁽ⁱ⁾ values within 0.05 MHz. The experimental results are in good agreement with the theoretical calculations. The barrier height to internal rotation of nitro group, 4.1±1.0 kcal/mol, was estimated from the GED analysis using a dynamic model. The equilibrium structure was also calculated using the experimental rotational constants for nitrobenzene isotopomers and theoretical rotation–vibration interaction constants.     

ClO<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack>/Al-MCM-41 nanoparticles as a solid acid catalyst for the synthesis of 2-amino-3-cyanopyridines

A one-pot four-component reaction of various types of aldehydes, acetophenone, malononitrile, and ammonium acetate was studied in the presence of perchlorated Al-MCM-41 (ClO ₄ ^? /Al-MCM-41) nanoparticles for the synthesis of 2-amino-3-cyanopyridines. Mesoporous Al-MCM-41 molecular sieves with the Si/Al molar ratios of 30, 40, and 50 were synthesized by the sol–gel method and ClO ₄ ^? /Al-MCM-41 with different calcination temperatures were prepared and characterized by SEM, TEM, XRD, FT-IR, potentiometric titration and, N₂ adsorption-desorption techniques. The characterization results show that ClO ₄ ^? /Al-MCM-41 with calcination temperature of 300 °C has the best catalytic activity for the synthesis of 2-amino-3-cyanopyridines. The catalyst is reusable many times with moderate loss in its activity.     

Thermal properties,phase transitions,vibrational and reorientational dynamics of [Mn(NH<Subscript>3</Subscript>)<Subscript>6</Subscript>](NO<Subscript>3</Subscript>)<Subscript>2</Subscript>

[Mn(NH₃)₆](NO₃)₂ crystallizes in the cubic, fluorite (C1) type crystal lattice structure (Fm \( \overline{3} \) m) with a = 11.0056 Å and Z = 4. Two phase transitions of the first-order type were detected. The first registered on DSC curves as a large anomaly at T _C1 ^h  = 207.8 K and T _C1 ^c  = 207.2 K, and the second registered as a smaller anomaly at T _C2 ^h  = 184.4 K and T _C2 ^c  = 160.8 K (where the upper indexes h and c denote heating and cooling of the sample, respectively). The temperature dependence of the full width at half maximum of the band associated with the δ_s(HNH)F_1u mode suggests that the NH₃ ligands in the high temperature and intermediate phase reorientate quickly with correlation times in the order of several picoseconds and with activation energy of 9.9 kJ mol^?1. In the phase transition at T _C2 ^c probably only a some of the NH₃ ligands stop their reorientation, while the remainders continue to reorientate quickly with activation energy of 7.7 kJ mol^?1. Thermal decomposition of the investigated compound starts at 305 K and continues up to 525 K in four main stages (I–IV). In stage I, ²/₆ of all NH₃ ligands were seceded. Stages II and III are connected with an abruption of the next ²/₆ and ¹/₆ of total NH₃, respectively, and [Mn(NH₃)](NO₃)₂ is formed. The last molecule of NH₃ per formula unit is freed at stage IV together with the simultaneous thermal decomposition of the resulting Mn(NO₃)₂ leading to the formation of gaseous products (O₂, H₂O, N₂ and nitrogen oxides) and solid MnO₂.     

Synthesis,DNA-binding properties and cytotoxicity evaluation of two copper(II) complexes based on curcumin

Two Cu(II) complexes based on curcumin, namely CuL ₂ ¹ [HL¹ = 1,7-bis[4-(2-oxymethylenepyridine)-3-methoxyl]phenyl-1,6-heptadiene-3,5-diketone] and CuL ₂ ² [HL² = 1,7-bis[4-(3-oxymethylene-2-chlorothiophene)-3-methoxyl] phenyl-1,6-heptadiene-3,5-diketone], have been synthesized and characterized by physico-chemical and spectroscopic methods. The interactions of calf thymus DNA (CT-DNA) with both complexes have been investigated by UV–Vis absorption, fluorescence and viscosity titration methods. Both complexes are found to interact with CT-DNA by intercalative binding modes. Evaluation of the cytotoxicities of the complexes against three human tumor cells showed that they have potent cytotoxicities against all three cell lines.     

Effect of the salting-out agent anion nature on the phase separation of a potassium salt–potassium bis(alkyl polyoxyethylene)phosphate–water systems

The effect the salting-out agent anion nature has on the temperature and concentration intervals of the existence of the separation area is established by analyzing the phase diagrams of pseudoternary KCl (KBr, KI, KNO₃, K₂SO₄, K₄P₂O₇)–potassium bis(alkyl polyoxyethylene)phosphate (oxyphos B)–water systems. It is concluded that the anionic salting-out capability is reduced in the order P₂O₇^4-> SO₄^2-> Cl^? > Br^?> NO₇^4-> SO₃^-> I^?. The thermodynamic parameters of phase separation used to interpret the results are calculated. The observed pattern of a change in the salting-out ability of the investigated salts relative to aqueous solutions of the surfactants is in good agreement with the lyotropic (Hofmeister) series.     

Pre-formulation of an oral cyclosporine free of surfactant

The purpose of this study was to develop a new oral cyclosporine A (CsA) formulation free of surfactant cremophor using cyclodextrin terpolymers (P-αβ-CD, P-βγ-CD and P-αγ-CD) as excipients in attempt to enhance its stability, dissolution rate and eliminate surfactant side effects. Two spray-dried dispersions (SDDs) containing poorly water-soluble CsA were prepared with either P-αβ-CD, P-βγ-CD or P-αγ-CD using water ( $ F_{{{\text{H}}_{2} {\text{O}}}} $ ) and ethanol (F _EOH) via spray-drying technique and characterized by scanning electron microscopy, powder X-ray diffraction, particle size distribution, circular dichroism (CD) and nuclear magnetic resonance along with the dissolution study which was compared to Neoral^® and Sandimmune^®. The results showed an interaction between CsA and P-αβ-CD, P-βγ-CD and P-αγ-CD without secondary structure change of CsA. The order of the CsA release from the terpolymers was ranked as follows: P-αγ-CD/CsA ( $ F_{{{\text{H}}_{2} {\text{O}}}} $ ) = Neoral^® > P-βγ-CD/CsA ( $ F_{{{\text{H}}_{2} {\text{O}}}} $ ) > P-αβ-CD/CsA ( $ F_{{{\text{H}}_{2} {\text{O}}}} $ ) > P-αγ-CD/CsA (F _EOH) > Sandimmune^® > P-αβ-CD/CsA (F _EOH) > P-βγ-CD/CsA (F _EOH). The results of ( $ F_{{{\text{H}}_{2} {\text{O}}}} $ ) could be explained by hydrophilisation and absence of crystallinity of CsA while maintaining part of its crystallinity in the case of formulations (F _EOH). In summary, developed SDD formulations P-αγ-CD/CsA ( $ F_{{{\text{H}}_{2} {\text{O}}}} $ ) revealed same dissolution profile as Neoral^® and better than Sandimmune^®. These systems seem to be stable to carry cyclosporine and release it, while preserving structure and thus, potentially, also maintaining cyclosporine activity.     

Structure of Aqueous Lithium Tetraborate Solution

The structure of aqueous lithium tetraborate solutions was investigated by species distribution calculation and synchrotron X-ray scattering. It shows that the dominant species in supersaturated solution at 298.15 K is B₄O₅(OH) ₄ ^2? and the minor species are B₃O₃(OH) ₅ ^2? , B₃O₃(OH) ₄ ^? and B(OH)₃. The ‘intramolecular’ structural parameters of B₄O₅(OH) ₄ ^2? , such as bond length and coordination number, were gives out using density function theory calculation. X-ray scattering study shows that the distance Li–O(H₂O)_I of [Li(H₂O)₄]⁺ is about 0.1983 nm with the coordination number(CN) 4 in tetrahedral configuration. The B–O(H₂O) distance in hydrated anion B₄O₅(OH)₄(OH₂) ₈ ^2? is 0.3662 nm with the CN 12. The Li⁺–B distance is about 0.3364 nm with a coordination number ~1.0. The temperature effect on solution structure was also discussed.     

Probing Structure,Thermochemistry, Electron Affinity and Magnetic Moment of Erbium-Doped Silicon Clusters ErSi<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 3–10) and Their Anions with Density Functional Theory

The lowest energy structures and electronic properties of ErSi _n (n = 3–10) and their anions were probed using the ABCluster global search technique combined with the PBE, TPSSh and B3LYP schemes. The lowest energy energies of neutral ErSi _n (n = 3–10) can be regarded as substituting a Si atom of the lowest energy structure of Si_n+1 with a Er atom. The additional electron effects on the geometries are very strong, resulting the lowest energy structures of ErSi _n ^? with n > 6 are different from their neutral counterparts. Starting from n = 7, the potential energy surfaces of ErSi _n ^? are very flat, resulting isomeric arrangements occur and functional dependence of the predicted most stable structures exist. The AEAs, VDEs and simulated PES of ErSi _n (n = 3–10) are reported. Introducing Er to Si cluster can significantly improve photochemical reactivity of the cluster. The 4f electron of Er atom in ErSi₄, ErSi _n ^? (n = 4, 7–10) prefers to take part in bonding. The total magnetic moments of ErSi _n and their anions are mainly provided by the 4f electrons of Er atom. The dissociation energies of Er from ErSi _n and their anions were evaluated to inspect relative stability.     

Thermal behavior analysis of halloysite selected from Inner Mongolia Autonomous Region in China

Thermal behavior of halloysite selected from Erdos, Inner Mongolia Autonomous Region in China, was investigated by thermogravimetry and differential thermal gravity (TG–DTG), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscope (SEM). The XRD results indicated that the mineralogical composition of halloysite sample was determined as 7 Å halloysite with the d ₍₀₀₁₎ value of 0.734 nm, a small amount of 10 Å halloysite with the d ₍₀₀₁₎ value of 0.998 nm, quartz, calcite, anhydrite, siderite, and analcite. The crystal chemical formula of halloysite specimen is (Ca_0.007Na_0.039K_0.048)(Al_1.935Fe _0.032 ³⁺ Mn _0.003 ²⁺ Ti _0.002 ⁴⁺ Mg _0.015 ²⁺ Ca _0.021 ²⁺ )₂ [(Si_1.935Al _0.065 ³⁺ )₂](OH)₄·2H₂O according to the oxygen atom method. The TG–DTG–DSC data showed that a small amount of water molecule layer in the interlayer and the dehydroxylation was observed at 493.6 °C. The XRD, FT-IR, and SEM data clearly show that the structure changes and dehydroxylation of the halloysite with the temperature increased from 200 to 1200 °C. The dehydration of the halloysite is followed by the loss of intensity and evolution of the OH vibration bands and the change in microstructure. Dehydroxylation is followed by the decrease in the intensity of the bands at 3696 and 3620 cm^?1, which is completely disappeared at 700 °C. The thermal behavior of halloysite was influenced by the mineralogy composition and impurities.     

Synthesis and characterization of a new monophosphate (C<Subscript>6</Subscript>H<Subscript>16</Subscript>N<Subscript>2</Subscript>)(H<Subscript>2</Subscript>PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

Chemical preparation, crystal structure, and NMR spectroscopy of a new trans-2,5-dimethylpiperazinium monophosphate are given. This new compound crystallizes in the triclinic system, with the space group P-1 and the following parameters: a = 6.5033(3), b = 7.6942(4), c = 8.1473(5) Å, α = 114.997(3), β = 92.341(3), γ = 113.136(3), V = 329.14(3) ų, Z = 1, and D_x = 1.565 g cm^?3. The crystal structure has been determined and refined to R = 0.030 and R _w(F ²) = 0.032 using 1558 independent reflections. The structure can be described as infinite [H₂PO₄] _n ^n? chains with (C₆H₁₆N₂)²⁺ organic cations anchored between adjacent polyanions to form columns of anions and cations running along the b axis. This compound has also been investigated by IR, thermal, and solid-state, ¹³C and ³¹P MAS NMR spectroscopies and Ab initio calculations.     

Radiation polymerization of methacrylates controlled by a chain transfer catalyst

The effect of γ-radiation dose and chain transfer catalyst on polymerization of methyl methacrylate (MMA) and copolymerization of MMA with hydroxyethyl methacrylate or triethylene glycol dimethacrylate has been investigated. The addition of 5 × 10^?4?10^?3 mol/L of bis[(difluoroboryl) isopropylpyridine dimethylglyoximato]cobalt(II) (Co(II)) makes it possible to produce macromonomers MM _n ⁼⁼ bearing terminal double bonds and having a degree polymerization of n = 2?40 and a polydispersity index of 1.05?1.15. It has been found that the degree polymerization of the macromonomers increases with the increasing γ-radiation dose and monomer conversion through the mechanism of the reversible β-cleavage of the terminal unit: R _k ^? + MM _n ⁼ ? MM _k+1 ⁼ + R _n-1 ^? followed by the living polymerization of both radicals. This reaction may compete with the catalytic chain transfer reaction and have a significant effect on the evolution of the molecular weight characteristics of the macromonomers during the course of MMA (co)polymerization.     

Adsorption of complex silver cyanides on Ag(111). Quantum chemical consideration

The interaction of AgCN molecules and Ag(CN)₂^?, Ag(CN)₃^2?, Ag(CN)₄^3? ions with the silver surface is studied based on the cluster model of the metal surface by quantum chemistry methods. The geometrical and energy parameters of the interaction of these species with the metal surface are assessed. As regards the strength of their chemical bond with the surface, these compounds form the following series: Ag(CN)₂^? < Ag(CN)₃^2? < AgCN < Ag(CN)₄^3?. The surface activity of silver-containing species is compared with regard to the solvent effect. It is found that Ag(CN)₂^? and Ag(CN)₃^2? anions exhibit close adsorbabilities on silver. Molecules AgCN are not accumulated on the surface because of their very low content in solution. The adsorption of Ag(CN)₄^3? is hindered due to a considerable value of degradation energy of this three-charged ion. In the adsorbed state, the ions Ag(CN)₂^? and Ag(CN)₃^2? represent stable compounds displaying no surface dissociation to yield compounds with the smaller coordination numbers.     

Synthesis, Crystal Structure and Characterization of a Mixed-Valence Keggin-Structural 12-Molybdophosphoric Acid Compound: NH4(C4N2H12)(C2N2H10)2[Mo 4 V Mo 8 VI PO40]·2H2O

A mixed-valence Keggin-structural 12-molybdophosphoric acid hydrate, NH₄(C₄N₂H₁₂)(C₂N₂H₁₀)₂ [Mo ₄ ^V Mo ₈ ^VI PO₄₀]·2H₂O (1), has been synthesized hydrothermally and characterized by single-crystal X-ray diffraction, elemental analysis, TG, XRD, IR, Raman, UV–Vis diffuse reflection spectrum and XPS spectrum. The compound 1 crystallizes in the monoclinic system with cell parameters of a = 20.668(4) Å, b = 10.827(2) Å, c = 21.508(4) Å, β = 117.070(3)°, V = 4,285.6(14) ų, and space group C _2/c, Z = 4 at 293 K. The final full-matrix least-squares refinement converged to R ₁ = 0.029 for the observed reflections (4,721) with I > 2σ(I) and wR ₂ = 0.065 for all data (4,837) and S = 1.048. Compared with another compound, (C₄N₂H₁₂)(C₂N₂H₁₀)₂[Mo₅P₂O₂₃] (2) (Chen et al., Chin J Struct Chem 30:1178, 2011), compound 1 was obtained via only changing molar ratio of reactants and the pH value of reaction system. Meanwhile, compound 1 contains the same two kinds of organonitrogen ligands, even their molar ratio, but entirely different space architecture and distinct heteropoly blue building block, [Mo ₄ ^V Mo ₈ ^VI PO₄₀]^7?. The crystal packing of 1 presents interesting 1D Zig-zag, 2D laminated and even 3D honeycomb-like configurations.     

Nongeneral Character of the Resonance Parameters Σ<Stack><Subscript>R</Subscript><Superscript>+</Superscript></Stack> of Silicon-, Germanium-, and Tin-Containing Substituents in Radical Cations

The resonance parameters σ _R ⁺ of substituents Y in radical cations YD^+· [where D is a π- or n-type center, and Y = MMe₃, CH₂MMe₃ (M = Si, Ge, Sn), C(SiMe₃)₃] depend on the nature of both Y and D. Using radical cations YD^+· (Y = CH₂SiMe₃, SnMe₃) as examples, it was found that the two conjugation parameters, constants σ _R ⁺ of substituents Y and perturbation energy calculated by the modified molecular orbital perturbation method, are linearly related to each other. The energies of donor and acceptor components of the overall resonance effect of CH₂SiMe₃ and SnMe₃ with respect to radical cation centers D^+· were estimated for the first time. The donor energy constituent in YD^+· is considerably greater than in neutral DY molecules.