Influence of Al2O3 Nanoparticles on the Thermal Stability of Ultra-Fine Grained Copper Prepared by High Pressure Torsion

Summary.  Ultra-fine grained (UFG) Cu (grain size 80 nm) containing 0.5 wt.% Al₂O₃ nanoparticles (size 20 nm) was prepared by high pressure torsion (HPT). Positron lifetime spectroscopy was employed to characterize the microstructure of this material, especially with respect to types and concentration of lattice defects. The evolution of microstructure with increasing temperature was studied by positron lifetime spectroscopy and X-ray diffraction measurements. The thermal stability of the Cu + 0.5 wt.% Al₂O₃ nanocomposite was compared with that of pure UFG Cu prepared by the same technique. The processes taking place during thermal recovery of the initial nanoscale structure in both studied materials are described. Received October 5, 2001. Accepted (revised) December 20, 2001     

Coordination compounds of nickel with trithiocyanuric acid. Part IV. Structure of [Ni(pmdien)(ttcH)] (pmdien = N,N,N′,N′,N′′-pentamethyldiethylenetriamine,ttcH3 = trithiocyanuric acid)

Ni^II mixed-ligand complexes of compositions [Ni(pmdien)(ttcH)] (1), [Ni(baphen)₂(ttcH)] · 4H₂O (2), [Ni-(dpa)(ttcH)(H₂O)] (3), [Ni(cyclam)(ttcH)] · 2H₂O (4), [Ni(hexaa)](ttcH) (5) and [Ni(hexab)(ttcH)] · 2H₂O (6), (baphen = 4,7-diphenyl-1,10-phenanthroline, dpa = 2,2-dipyridylamine, cyclam = 1,4,8,11-tetraazacyclotetradecane, hexaa = 1,3,6,9,11,14-hexaazatricyclo[12.2.1.1^6,9]-octadecane, hexab = 1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane) have been prepared and characterized by means of i.r., u.v.–vis. spectroscopies and magnetochemical measurements. The redox properties of the complexes were studied by cyclic voltammetry. The crystal and molecular structure of [Ni(pmdien)(ttcH)] was determined. The nickel atom is penta-coordinated by three N atoms of pmdien, and by S and N atoms of trithiocyanurate(2–) anion.     

Gas phase intramolecular proton transfer in cationized glycine and chlorine substituted derivatives (M-Gly, M = Na+, Mg2+, Cu+, Ni+, and Cu2+): existence of Zwitterionic structures?

The intramolecular proton transfer in cationized glycine and chlorine substituted derivatives with M = Na+, Mg2+, Ni+, Cu+, and Cu2+ has been studied with the three parameter B3LYP density functional method. The coordination of metal cations to the oxygens of the carboxylic group of glycine stabilizes the zwitterionic structure. For all monocations the intramolecular proton transfer occurs readily with small energy barriers (1-2 kcalmol(-1)). For the dication Mg2+ and Cu2+ systems, the zwitterionic structure becomes very stable. However, whereas for Mg2+, the proton transfer process takes place spontaneously, for Cu2+ the reaction occurs with an important energy barrier. The substitution of the hydrogens of the amino group by chlorine atoms decreases the basicity of nitrogen, which destabilizes the zwitterionic structure. For monosubstituted glycine complexed with Na+, the zwitterionic structure still exists as a minimum, but for disubstituted glycine no minimum appears for this structure. In contrast, for Mg2+ complexed to mono- and disubstituted glycine, the zwitterionic structure remains the only minimum, since the enhanced electrostatic interaction with the dication overcomes the destabilizing effect of the chlorine atoms.     

Synthesis and crystal structure of [(η3-C3H5)(CO)2Mo(μ-S2CPCy3)-Mo(η3-CH2CMeCH2)(CO)2]

A novel dimolybdenum complex [(³-C₃H₅)(CO)₂Mo(-S₂CPCy₃)Mo(³-CH₂CMeCH₂)(CO)₂], obtained by reacting the [(CO)₂(³-C₃H₅)Mo(-S₂CPCy₃)Mo(CO)₃]^– anion with an excess of ClCH₂CMe=CH₂, has been characterized by i.r., ³¹P{¹H}, ¹H- and ¹³C-n.m.r. spectroscopy and by elemental analysis. The crystal structure of the complex, determined by X-ray diffraction, shows a definite preference for the central carbon of the S₂CPCy₃ bridge to bind to the Mo(2) atom coordinated by ³-2-methylallyl, rather than the Mo(1) atom attached to unsubstituted ³-allyl ligand.     

Barreleneiridium(I) complexes. Crystal structures of [Ir(Me3TFB)(η6-C6H4Me2)]ClO4 and [Ir(TFB)(η5-PhNPh2)]BF4·CH2Cl2 (TFB = tetrafluorobenzobarrelene)

A new series of cationic areneiridium(I) complexes of formula [Ir(barrelene)(arene)]⁺ or [Ir(barrelene)(PhNRPh)]⁺ (R= Ph or H) have been synthesized from neutral iridium complexes of the type [IrY(barrelene)]_x (barrelene = Me₃TFB, Y = Cl or OMe (x = 2), Y = acac (x = 1); barrelene = TFB, Y = OMe (x = 2), Y = acac (x = 1)). The crystal structures of [Ir(Me₃TFB)(1,4-C₆H₄Me₂)]ClO₄ and [Ir(TFB)(PhNPh₂)]BF₄·CH₂Cl₂ have been determined by X-ray diffraction. They crystallize in the space groups Pbca and Pna2₁ respectively with lattice constants of 17.6947(11), 15.8072(10), 16.0019(11) Å and 9.8059(2), 20.8097(9), 14.3367(4) Å. Final R factors were 0.063 and 0.042 for the observed data. Both complexes show a staggered arrangement between the arene and the TFB moieties and deviation from planarity of the coordinated arene ligands. In the second complex the IrC and NC distances, the CNC angle, the type of arene puckering, and the spectroscopic data indicate a distortion of the coordinated arene towards a η⁵-coordinated iminocyclohexadienyl form.     

Analysis of99Tc atmospheric samples

The analysis of⁹⁹Tc was carried out in filter, peat and rainwater samples. A solvent extraction technique was used to separate Tc from them, where tributylphosphate was the extracting agent. Radiochemical yield was obtained by using^99mTc as an internal tracer. A typical value of 60% was found for it. However, problems encountered in its determination are discussed in the text. Additionally, rainwater samples were analyzed for¹³⁷Cs. This was adsorbed in ammonium phosphomolibdate. Radiochemical yield was obtained by using¹³⁴Cs as an internal tracer.Work partially supported under Contract CAICYT No. 2849/83.     

Extraction-spectrophotometric determination of iron with 2-(2′-benzothiazolylazo)-4,6-dimethylphenol

An extraction-spectrophotometric method for the determination of trace amounts of iron based on its extraction into chloroform with 2-(2-benzothiazolylazo)-4,6-dimethylphenol (BTADMP) from a pH 6.5 medium has been developed. The extracted 12 FeBTADMP complex species allow the determination of 4–30gmg of iron (=3.92×10⁴1·mol^–1·cm^–1 at 790 nm). The method is highly selective and has been applied to the determination of iron in polymineral-polyvitamin pharmaceutical products.     

Reaction of N-(4-pyridylmethyl)benzamide N-oxides with ethyl cyanoacetate in the presence of acetic anhydride

Reaction of N-(4-pyridylmethyl)benzamide N-oxides 2a-f with ethyl cyanoacetate in the presence of acetic anhydride yield dimerization compounds 3a-f and (E)-ethyl 2-cyano-3-(4-pyridyl)-3(benzoylamino)acrylates 4a-f , which react with hydrazine to give 4-cyano-3-(4-pyridyl)-3-pyrazolin-5-one 9 and the corresponding benzamides 10a-f .     

Sensitive determination of probenecid in urine samples by reversed-phase liquid chromatography and UV-visible detection using solid-phase extraction techniques for sample clean-up

Summary This study describes a rapid method for the determination of probenecid in human urine by liquid chromatography with UV detection at 254 nm, after clean-up through a C8 solid-phase extraction column. Liquid chromatography was carried out on a C18-bonded phase using an acetonitrile-acetate buffer (pH=4) gradient elution. Ethacrynic acid was used as internal standard. The system has been applied to the determination of probenecid in the 0.10–100.0 g/ml concentration range; the limit of detection was 5 ng/mL.