Double photoionisation spectra of small molecules and a new empirical rule for double ionisation energies

Complete double photoelectron spectra are presented for 18 small molecules where the location of charges in the cations and dications is relatively clearly defined. The data demonstrate the importance of a coulombic repulsion contribution to the double ionisation energies. Examination of data for a wide range of molecules leads to a new empirical rule to calculate double ionisation energies from the molecules’ single ionisation energies and maximum dimensions. Where single and double ionisation energies are known the rule allows the deduction of plausible intercharge distances.     

2D and 3D supramolecular assemblies of double cyclopalladated azobenzenes realized by C-H?Cl-Pd, π?π and C-H?π interactions

The double cyclopalladated complex with azobenzene, μ-[(E)-1,2-diphenyldiazene-C^2,8, N^1,2]-di-[chloro(dimethylsulfoxide)palladium(II)]; (DMSO)PdCl(μ-C₆H₄NNC₆H₄)(DMSO)PdCl (1) and its analogous complex with DMF as ancillary ligand, (DMF)PdCl(μ-C₆H₄NNC₆H₄)(DMF)PdCl; μ-[(E)-1,2-diphenyldiazene-C^2,8,N^1,2]-di-[chloro(dimethylformamide)palladium(II)] (2a) were synthesized and the function of cyclopalladated moiety in molecular assembling in the solid state is illustrated by their crystal packings. The polymorphism of 2a and 2b is discussed. The crystal structures reveal assemblies with molecular components self-organized by C-H?Cl-Pd hydrogen bonds, π?π, and C-H?π interactions. The double cyclopalladated complexes of azobenzene, with two Pd-Cl moieties participating in the hydrogen bond formation and π-conjugated system involved in the π?π or C-H?π interactions, represent a new class of building blocks for construction of solid state supramolecular assemblies.     

Synthesis and properties of the double perovskites La2NiVO6, La2CoVO6, and La2CoTiO6

The double perovskites La₂CoVO₆, La₂CoTiO₆, and La₂NiVO₆, are described. Rietveld fitting of neutron and powder X-ray diffraction data show La₂NiVO₆ and La₂CoVO₆ to have a disordered arrangement of B-cations whereas La₂CoTiO₆ shows ordering of the B-cations (with ∼5% Co/Ti inversion). Curie-Weiss fits to the linear region of the 1/χ plots reveal Weiss temperatures of −107, −34.8, and 16.3 K for La₂CoVO₆, La₂CoTiO₆, and La₂NiVO₆, respectively, and magnetic transitions are observed. La₂CoTiO₆ prepared by our method differs from material prepared by lower-temperature routes. A simple antiferromagnetic spin model is consistent with the data for La₂CoTiO₆. These compounds are semiconductors with bandgaps of 0.41 (La₂CoVO₆), 1.02 (La₂CoTiO₆) and 0.45 eV (La₂NiVO₆).     

Synthesis of chiral β-3-amino-2-hydroxyalkanoates and 3-alkyl-3-hydroxy-β-lactams by double asymmetric induction

Reactions of chiral (2S)-enolates of dioxolan-4-ones, derived from lactic, mandelic, and phenyllactic acids, with aliphatic (S_S)- and (S_R)-tert-butylsulfinyl aldimines afforded conformationally restrained C2-disubstituted N,O-orthogonally protected 3-amino-2-hydroxyalkanoates in the form of N-sulfinyl protected 1′-aminodioxolan-4-ones. The product distribution showed that there is significant kinetic selectivity, due to the presence of ‘matched’ and ‘mismatched’ components, between the (S)- or (R)-tert-butylsulfinyl aldimines and the (2S)-enolates of the 1,3-dioxolan-4-ones. Selective methoxide-induced removal of the acetal group of the N-sulfinyl-1′-aminodioxolanones yielded the corresponding N-sulfinyl protected methyl alkanoates. In addition, the selective acid-induced removal of the sulfinyl group of the N-sulfinyl-1′-aminodioxolanones provided the corresponding N-unprotected 1′-aminodioxolanones, whose base-induced cyclization afforded the corresponding β-lactams.     

Magnesium substitution in Nd0.7Sr0.3MnO3

Magnesium substitution in Nd_0.7Sr_0.3MnO₃ has been studied by neutron powder diffraction. Polycrystalline samples of nominal compositions Nd_0.7Sr_0.3Mn_1−yMg_yO₃ with y=0.0, 0.1, 0.2 and 0.3 were synthesized by the standard solid-state reaction method. Rietveld refinements of the neutron powder diffraction data showed that all samples had distorted perovskite structure of orthorhombic symmetry. Mg initially preferred to substitute for Nd and only at Mg concentration greater than 0.1, a substantial substitution for Mn occurred. Our study also showed that Mg-substitution did not change the crystal structure of Nd_0.7Sr_0.3MnO₃.     

咪唑啉纤维树脂分离富集/ICP-MS测定矿石中的痕量铂(Ⅳ)

本文提出了咪唑啉纤维树脂分离富集/ICP-MS测定矿石中痕量铂(Ⅳ)的方法。实验考察了影响咪唑啉纤维树脂分离富集痕量Pt(Ⅳ)的酸度、流速、洗脱液的组成、体积等因素,结果发现:在20%的王水介质中,Pt(Ⅳ)能定量吸附于树脂上并与大量其它金属分离;被吸附的Pt(Ⅳ)可用5%硫脲-1%HCl溶液定量洗脱,ICP-MS测定Pt(Ⅳ)的回收率为87%~102%。所建立的方法应用于硫镍矿管理样分析,其测定结果与推荐值吻合。     

Synthesis and crystal structure of three silver indium double phosphates

Three new silver indium double phosphates Ag₃In(PO₄)₂ (I), β-(II) and α-Ag₃In₂(PO₄)₃ (III) were synthesized by solid state method (I and II—700 °C, III—900 °C). Compounds I and II crystallize into a monoclinic system (I—sp. gr. C2/m, Z=2, a=8.7037(1)Å, b=5.4884(1)Å, c=7.3404(1)Å, β=93.897(1)°; II—sp. gr. C2/c, Z=4, a=12.6305(1)Å, b=12.8549(1)Å, c=6.5989(1)Å, β=113.842(1)°), and compound III crystallize into a hexagonal system (sp. gr. R-3c, Z=6, a=8.9943(1)Å, c=22.7134(1)Å). Their crystal structures were determined by the Rietveld analysis (I—R_p=6.47, R_wp=8.54; II—R_p=5.67, R_wp=6.40; III—R_p=7.30, R_wp=9.91). Structure of Ag₃In(PO₄)₂ is related to the sodium chromate structure type and is isotypic to α-Na₃In(PO₄)₂. The polymorphous modifications of β- and α-Ag₃In₂(PO₄)₃ are isostructural to sodium analogs (β- and α-Na₃In₂(PO₄)₃) and are related to alluaudite (II) and NASICON (III) structure types. Compounds I and II are not stable at temperature above 850 °C. Ag₃In(PO₄)₂ is decomposed providing silver orthophosphate Ag₃PO₄ and α-Ag₃In₂(PO₄)₂. β-Ag₃In₂(PO₄)₃ is transformed to α-Ag₃In₂(PO₄)_3.     

Study of a Catalytic Mechanism in Additive Differential Pulse Techniques

The new electrochemical double pulse technique, known as additive differential normal pulse voltammetry (ADNPV) when there is no restriction on the duration of both pulses, and additive differential pulse voltammetry (ADPV) when t₂?t₁, has been applied to a pseudo‐first‐order catalytic mechanism. The expressions obtained here are applicable to planar and spherical electrodes, of any radius. This is of great interest since the size of the electrode plays an important role in the preponderating of diffusive and kinetics processes. The signal obtained with this technique presents the same morphological characteristics as the triple pulse technique, double differential pulse voltammetry (DDPV) and is more advantageous than DDPV and than the double pulse one, differential pulse voltammetry (DPV).     

Double pulse laser-induced breakdown spectroscopy of explosives: Initial study towards improved discrimination

Detecting trace explosive residues at standoff distances in real-time is a difficult problem. One method ideally suited for real-time standoff detection is laser-induced breakdown spectroscopy (LIBS). However, atmospheric oxygen and nitrogen contributes to the LIBS signal from the oxygen- and nitrogen-containing explosive compounds, complicating the discrimination of explosives from other organic materials. While bathing the sample in an inert gas will remove atmospheric oxygen and nitrogen interference, it cannot practically be applied for standoff LIBS. Alternatively, we have investigated the potential of double pulse LIBS to improve the discrimination of explosives by diminishing the contribution of atmospheric oxygen and nitrogen to the LIBS signal. These initial studies compare the close-contact (< 1 m) LIBS spectra of explosives using single pulse LIBS in argon with double pulse LIBS in atmosphere. We have demonstrated improved discrimination of an explosive and an organic interferent using double pulse LIBS to reduce the air entrained in the analytical plasma.     

Diffusion Coefficients of Tris(<Emphasis Type="Italic">β</Emphasis>-diketonato)ruthenium Complexes of Different Charge Numbers in Acetonitrile Solutions,Measured by Chronoamperometry

The diffusion coefficients of several tris(β-diketonato) ruthenium complexes in acetonitrile solutions containing a supporting electrolyte were determined by chronoamperometry. The diffusion coefficients of the charged complexes, which were produced by electrochemical oxidation or reduction, were also determined by double potential step chronoamperometry. Two kinds of radii of the complexes were evaluated. One was the Van der Waals radius and the other was the geometric distance from the center of the complex to the outer surface of the farthest atom. The latter quantity was determined from X-ray diffractometric data. The diffusion coefficients of the neutral complexes were discussed on the basis of the Stokes-Einstein equation. Those of charged complexes could not be explained by the theoretical equation presented by Hubbard and Onsager.