Synthesis and characterization of dichlorodicarbonylruthenium(II) complexes of oxygen,sulphur and nitrogen donor ligands

Complexes of dichlorodicarbonylruthenium(II) of formula [RuCl₂(CO)₂L₂] (L = tetramethylthiourea, monomethylthiourea, dimethylthiourea, pyridine 2-thiol, piperidine or pyridine) and [RuCl₂(CO)₂L′ (L′= 1,2-diaminoethane or tetramethylurea), have been prepared. The complexes were characterized by their IR, NMR and elemental analyses.     

Core-level electronic spectra in ADC(2) approximation for polarization propagator: Carbon monoxide and nitrogen molecules

An effective ab initio approach to core-level electronic spectral studies is discussed. The approach uses polarization propagator theory in a second-order algebraic diagram construction ADC(2) approximation for calculating the characteristics of electron transitions; it also uses the linear vibronic model LVM for investigating the vibrational structure of transitions. The core excitation specialization of ADC(2) is achieved by introducing the core valence separation (CVS) approximation. K-excitation spectra of CO and N₂ molecules are calculated to examine the potential of the approach. The calculated spectra and the available experimental data are analyzed to characterize the method. A number of additional facts of methodological and practical value are found, and new transitions are predicted. It is concluded that ADC(2)/CVS/LVM is a promising approach to problem solving in core level spectroscopy, which requires qualitatively reliable theoretical estimations. Translated fromZhurnal Strukturnoi Khimii, Vol. 41, No. 3, May–June, 2000, pp. 590-604.     

Complexation of nitrogen and sulphur donor Schiff's base ligand to Cr(III) and Ni(II) metal ions: synthesis, spectroscopic and antipathogenic studies

2,6-diacetyl pyridine based ligand was synthesized by the reaction of 2,6-diacetyl pyridine with thiocarbohydrazide in presence of acetic acid. The coordination compounds with Cr(III) and Ni(II) metal ions having [Cr(L)X]X2 and [Ni(L)X]X compositions (where L=ligand and X=NO3-, Cl- and CH3COO-) were synthesized and characterized by physicochemical and spectral studies. The studies like elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, UV-Vis, NMR, mass and EPR reveal that the complexes are octahedral. The compounds were examined against the pathogenic fungal and bacterial strains like Alternaria brassicae, Aspergillus niger, Fusarium oxysporum, Xanthomonas compestris and Pseudomonas aeruginosa. A. niger causes the diseases Apergillosis and Otomycosis in humans.     

Multicomponent analysis of poly(propylene) using fractionation,tacticity and molecular weight data

Heterogeneous Ziegler-Natta catalysts are known to contain multiple catalytic sites and produce polymers that contain multiple components. An approach is described in this work that combines fractionation, ¹³C NMR and molecular weight distribution data to determine the number and the characteristics of the different components found in the polymer. The methodology is applied to published data on poly(propylene). The analyses indicate that poly(propylene) made with heterogeneous Ziegler-Natta catalysts consists of at least four components. Three of these components obey enantiomorphic-site models, and the fourth component obeys Bernoullian model.     

Energy-dispersive x-ray fluorescence analysis for sulphur,chlorine, potassium and calcium in aerosols

Problems in the use of x-ray spectrometry for the fast multi-element analysis of environmental samples such as aerosols collected on filters arise from absorption of the fluorescence intensity in the filter and in the collected matter. A procedure is described for the determination of the elements sulphur to calcium in aerosols collected on Whatman 41 filters. Two methods are compared for deconvolution of the spectra. These are based on counting in fixed energy channels or on non-linear least-squares analysis. Corrections for absorption effects have been calculated. Calibration is done with thin film standard deposits. The accuracy of the method is better than 15%. Difficulties in ascertaining the chlorine content of the filter are discussed. The evaporation of the chlorine fraction from the filter was studied in detail.     

Carbon and nitrogen distribution in the sediments of lagoon of Ravenna (Italy)

The distribution and the origin of carbon and nitrogen in sediments of an Italian lagoon--located north-east of Ravenna town--were investigated. From 1957 to 1976, the lagoon had been affected by a strong industrial pollution due to an important petrochemical complex. At present, industrial and domestic waste waters undergo a treatment process before being discharged into the lagoon. Sediment samples from 10 locations throughout the lagoon were analysed, in order to document the spatial and vertical distribution of C and N. Data show a very strong variability (organic carbon content varies between 8.9% and 0.14%) and the highest values were found in the immediate vicinity of the industrial discharge. Sediment organic matter shows allochthonous origin in proximity of industrial discharge and autochthonous origin in the remaining areas.     

Carbon dots codoped with nitrogen and sulfur are viable fluorescent probes for chromium(VI)

Microchimica Acta - Carbon dots codoped with nitrogen and sulfur (N,S-CDs) were synthesized by a single-step hydrothermal method. The N, S-CDs were characterized by transmission electron...     

Determination of sulphur species arising from the reaction of sulphur and sulphide in a (K, Na)SCN eutectic melt

Sulphur and sulphide ions react in (K,Na)SCN eutectic melt with the formation of polysulphide. The electrolytic oxidation of SCN(-) at 155 degrees forms S(4) which gives S(2-)(5) with S(2-); at 165 degrees the sulphur electrogenerated is S(2) that reacts according to S(2) + S(2-) = S(2-)(3). The equilibrium constants of these reactions have been obtained by voltammetric measurements. The formation of S(2) at 155 degrees by irradiation from a xenon lamp was confirmed. The S(2) reacts with S(2-) to give S(2-)(3), and the equilibrium constant for this reaction is the same as that found for the reaction at 165 degrees .     

Carbon isotopic ratio analysis by gas chromatography/combustion/isotope ratio mass spectrometry for the detection of gamma-hydroxybutyric acid (GHB) administration to humans

Since GHB (gamma-hydroxybutyric acid) is naturally produced in the human body, clinical and forensic toxicologists must be able to discriminate between endogenous levels and a concentration resulting from exposure. To suggest an alternative to the use of interpretative concentration cut-offs, the detection of exogenous GHB in urine specimens was investigated by means of gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). GHB was isolated from urinary matrix by successive purification on Oasis MCX and Bond Elute SAX solid-phase extraction (SPE) cartridges prior to high-performance liquid chromatography (HPLC) fractioning using an Atlantis dC18 column eluted with a mixture of formic acid and methanol. Subsequent intramolecular esterification of GHB leading to the formation of gamma-butyrolactone (GBL) was carried out to avoid introduction of additional carbon atoms for carbon isotopic ratio analysis. A precision of 0.3 per thousand was determined using this IRMS method for samples at GHB concentrations of 10 mg/L. The (13)C/(12)C ratios of GHB in samples of subjects exposed to the drug ranged from -32.1 to -42.1 per thousand, whereas the results obtained for samples containing GHB of endogenous origin at concentration levels less than 10 mg/L were in the range -23.5 to -27.0 per thousand. Therefore, these preliminary results show that a possible discrimination between endogenous and exogenous GHB can be made using carbon isotopic ratio analyses.     

Towards universal potentials for (H2)2 and isotopic variants: post-Born-Oppenheimer contributions

Adiabatic corrections are evaluated for the interaction of two hydrogen molecules (H(2))(2) and isotopic variants. Their contribution to the cluster formation amount up to 10% of the interaction energy. Added to the best ab initio Born-Oppenheimer isotropic potential, they correct especially its short range repulsive part. Calculations of second virial coefficients are improved in general, with an impressive agreement with experiments for gaseous D(2) in a large range of temperatures. The potentials are available in both analytical and numerical forms.     

Separation scheme for the determination of alkali metals (K, Rb, Cs), alkaline earths (Sr, Ba) and rare earths (Ce, Nd, Sm, Eu) in silicate materials by isotopic dilution analysis

A scheme is outlined for the separation of Li, K, Rb, Cs, Sr, Ba, Ce, Nd, Sm and Eu from silicate materials. The elements are separated by cation-exchange to provide groups suitable for mass spectrometric analysis, and are then further purified by anion-exchange. Results obtained by isotopic dilution analysis are reported for G-1, W-1, and the Harwell meteorite-in these measurements the alkali metals were determined separately from the other elements. Requirements are discussed for combining the procedures to form a more comprehensive method for use with a single sample.     

Advances in field-flow fractionation for the analysis of biomolecules: instrument design and hyphenation

Field-flow fractionation (FFF) separates analytes by use of an axial channel-flow and a cross-field. Its soft separation capability makes it an ideal tool for initial fractionation of complex mixtures, but large elution volumes and high flow rates have limited its applicability without significant user handling. Recent advances in instrumentation and miniaturization have successfully reduced channel size and elution speed, and thus the volume of each fraction, making it possible to conveniently couple FFF with orthogonal separation techniques for improved resolution. More detailed analysis can also be performed on the fractions generated by FFF by use of diverse analytical techniques, including MS, NMR, and even X-ray scattering. These developmental trends have given FFF more power in the analysis of different types of molecule, and will be the direction of choice for further advances in FFF technology.     

Kinetic 12C/13C isotope fractionation by invertase: evidence for a small in vitro isotope effect and comparison of two techniques for the isotopic analysis of carbohydrates

The natural ¹³C/¹²C isotope composition (δ¹³C) of plants and organic compounds within plant organs is a powerful tool to understand carbon allocation patterns and the regulation of photosynthetic or respiratory metabolism. However, many enzymatic fractionations are currently unknown, thus impeding our understanding of carbon trafficking pathways within plant cells. One of them is the ¹²C/¹³C isotope effect associated with invertases (EC 3.2.1.26) that are cornerstone enzymes for Suc metabolism and translocation in plants. Another conundrum of isotopic plant biology is the need to measure accurately the specific δ¹³C of individual carbohydrates. Here, we examined two complementary methods for measuring the δ¹³C value of sucrose, glucose and fructose, that is, off‐line high‐performance liquid chromatography (HPLC) purification followed by elemental analysis and isotope ratio mass spectrometry (EA‐IRMS) analysis, and gas chromatography‐combustion (GC‐C)‐IRMS. We also used these methods to determine the in vitro ¹²C/¹³C isotope effect associated with the yeast invertase. Our results show that, although providing more variable values than HPLC～EA‐IRMS, and being sensitive to derivatization conditions, the GC‐C‐IRMS method gives reliable results. When applied to the invertase reaction, both methods indicate that the ¹²C/¹³C isotope effect is rather small and it is not affected by the use of heavy water (D₂O). Copyright © 2009 John Wiley & Sons, Ltd.