Synthesis and structures of silicon-, germanium- and tin-containing tungsten imido alkyl complexes (ArN)2W(CH2EMe3)2 (E = Si, Ge, Sn)

The novel silicon-, germanium- and tin-containing imido alkyl complexes of tungsten of the type (ArN)₂W(CH₂EMe₃)₂ (; E = Si (1), Ge (2), Sn (3)) have been prepared by the reactions of (ArN)₂WCl₂(dme) (dme = 1,2-dimethoxyethane) with heteroelement-containing alkyllithium or Grignard reagents Me₃ECH₂Li (E = Si, Ge), Me₃ECH₂MgCl (E = Ge, Sn). The title compounds were isolated in high yields as crystalline solids and characterized by elemental analysis, IR, ¹H, ¹³C, ²⁹Si and ¹¹⁹Sn NMR spectroscopy and X-ray diffraction studies. The geometry of the W atoms in the compounds can be described as a distorted tetrahedron.     

Investigations and application in piezoelectric phenol sensor of Langmuir-Schäfer films of a copper phthalocyanine derivative functionalized with bulky substituents

An octa-substituted copper phthalocyanine was dissolved in chloroform and spread on ultrapure water subphase in a Langmuir trough. The floating films were characterized at the air–water interface by the Langmuir isotherm, Brewster angle microscopy, and UV–Vis reflection spectroscopy and transferred by Langmuir–Schäfer technique on a silicon substrate, and thickness, refractive index, and extinction coefficient of the phthalocyanine derivative thin film were calculated by means of spectroscopic ellipsometry. A different number of layers were deposited using Langmuir–Schäfer method onto QCM crystals, and the active layers were tested as sensors for the detection of phenols in aqueous solution. The piezoelectric sensor response, totally reversible, is influenced by the number of transferred layers and by the nature of the substituent; on the contrary, the pK_a value of the injected analytes slightly affects the device performances. Repeatability of the sensor responses was tested, and the frequency variation appears unchanged at least for 100 days.     

Local particle densities and global multiplicities in central heavy ion interactions at 3.7, 14.6, 60 and 200A GeV

The energy and centrality dependence of local particle pseudorapidity densities as well as validity of various parametrizations of the distributions are examined. The dispersion, , of the rapidity density distribution of produced particles varies slowly with centrality and is 0.80, 0.98, 1.21 and 1.41 for central interactions at 3.7, 14.6, 60 and 200A GeV incident energy, respectively, is found to be independent of the size of the interacting system at fixed energy. A novel way of representing the window dependence of the multiplicity as normalized variance versus inverse average multiplicity is outlined.     

Multiplicities in84Kr interactions in emulsion at 800–950 MeV/nucleon

Inelastic interactions induced by⁸⁴Kr nuclei at 800–950 MeV/nucleon have been studied using a high angular resolution emulsion detector. Data on multiplicities of the produced particles, projectile and target fragments are shown. Comparisons with cascade calculations have been performed.We thank to Swedish Research Council for Natural Sciences for the financial support. Scanning and measurements performed by E.G. Broomé and V. Kopljar are acknowledged.     

Synthesis and Structure of the Complex [Mo3(μ3-S)(μ2-S2)3(Et2NCS2)3 +Br-

Tri-₂-disulfido-₃-thiotris(diethyldithiocarbamato)-S,S'-triangle-trimolybdenum bromide [Mo₃(₃-S)(₂-S₂)₃(Et₂NCS₂)₃ ⁺Br^- was obtained and characterized.     

Synthesis and structures of silicon-, germanium-, and tin-containing imido-alkyl molybdenum complexes (ArN)2Mo(CH2EMe3)2 (E = Si, Ge, Sn)

New silicon-, germanium-, and tin-containing imido-alkyl molybdenum complexes (ArN)₂Mo(CH₂EMe₃)₂ (Ar is 2,6-diisopropylphenyl; E = Si (1), Ge (2), Sn (3)) were prepared in the crystalline state in 58–66% yields by the reactions of the (ArN)₂MoCl₂(DME) complex with alkyllithium derivatives Me₃ECH₂Li (E = Si or Ge) or the Grignard reagents Me₃ECH₂MgCl (E = Ge or Sn). The structures of complexes 1–3 and the known analog (ArN)₂Mo(CH₂Bu^t)₂ (4) were established by X-ray diffraction analysis. Complexes 1–3 were found to be isostructural. The coordination environment about the Mo atom can be described as a distorted tetrahedron. Complex 4 has a similar structure. The Mo-C distance tends to decrease with increasing electron donating ability of the EMe₃ group.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 597–600, March, 2005.     

Destructive effect of polystyrene sulfonate on the structure of hemoproteins

The mechanism of the destruction of horse heart hemoglobin (Hb) and spermwhale muscle myoglobin (Mb), two hem-containing proteins, by polystyrene sulfonate, an anionic polyelectrolyte, was studied. Measurements of the optical absorption of the prostetic group of the hem in the visible spectrum and of the circular dichroism in the absorption bands of the peptide groups and aromatic amino acid residues demonstrated that the compact structure of both proteins experiences destruction in the presence of polystyrene sulfonate (PSS) at PSS concentrations ten times as low as that of the protein (in wt %) and that the content of α-helix structure in Hb and Mb decreases from 81% in the native state to 43% in their complexes with PSS. The distinctions in the mechanisms of the destruction of Hb and Mb by PSS were found to be as follows: (1) in contrast to Mb, Hb forms insoluble complexes with PSS at low PSS concentrations and (2) Mb-PSS solutions at Mb-to-PSS ratios >1 were found to contain free hems (that absorb at 397 nm), a feature not observed for Hb; the kinetics of the destruction of both the proteins by the polyelectrolyte was demonstrated to be a two-stage process. The first stage of the destruction of Hb (τ ≈ 24.5 s) was found to be four times as slow as that of Mb (τ ≈ 6 s); the second (slow) stage had a halftime of ～6 h for both the proteins under study. To determine the localization of regions at the protein molecule surface that are capable of binding polyelectrolyte molecules, the distribution of the electrostatic potential over the surface of the Hb and Mb molecules was numerically calculated with the help of the Poisson-Boltzmann equation at pH 6.2 and an ionic strength of 100 mmol/l. Based on experimental and theoretical studies of the mechanism of the interaction of the polyelectrolyte with the proteins, the structural-functional properties of proteins responsible for their destruction by the polyelectrolyte are determined.     

Chromatographic separation of paracetamol,caffeine, and aspirin on an adsorbent with immobilized nitrile groups and the analysis of Askofen P tablets

The chromatographic properties of the pharmaceutical preparations of paracetamol, caffeine, and aspirin are studied on adsorbents with immobilized nitrile groups. The effects of the concentration of acetonitrile and potassium phosphate in the mobile phase and the pH of the mobile phase on the retention of analytes and a possible additive, salicylic acid, are studied. In comparison to a column with a C18 adsorbent used earlier for routine analysis, the chromatograms obtained are characterized by higher separation efficiency, while the proposed separation procedure is more cost-effective and rapid.     

Use of supercritical fluids in inorganic analysis

The possibilities, advantages, shortcomings, and prospects of using supercritical fluids for separating and extracting metal complexes with organic reagents are considered. The theoretical bases of supercritical fluid chromatography and factors influencing the separation of metal complexes (nature of the organic reagent, solubility of reagents and complexes in a supercritical fluid, type of column, motionless phase, addition of a modifier into the mobile phase, and the test solvent) are discussed. The processes occurring in complexes during chromatography are discussed. The bases of supercritical fluid extraction and factors influencing extraction of metals (nature and solubility in a supercritical fluid of an organic reagent and complexes; concentration and ways of introducing the reagent into the system; addition of the modifier, water, and surfactants; the collector; and the matrix) are considered. The possibilities of methods for determining metals in various objects are shown.     

An immunochemical test for rapid screening of zearalenone and T-2 toxin

An immunochemically based test for non-instrumental simultaneous detection of zearalenone (ZEA) and T-2 toxin (T2) in feed was developed. The method combines clean-up of sample extract, pre-concentration of analytes by immunoextraction and immunodetection through the enzymatic reaction of horseradish peroxidase (HRP). The test is housed inside a standard 1-mL solid-phase extraction column and consists of three layers: two test layers (one for ZEA and another for T2) with immobilised specific antibodies and one control layer with bound anti-HRP antibodies. Feed extract was passed through an additional column with clean-up layer, which was disconnected after extract application. Total assay time was about 15 min for six samples and detection time was 4 min after chromogenic substrate application. Under optimised conditions a cut-off level for ZEA and T2 of 100 µg/kg was established. Different feed types were analysed for ZEA and T2 contamination by the proposed method and results were confirmed by LC-MS/MS.