Growth process of TiC clusters from Ti nanoparticles with evaporated carbon layer

Titanium carbide formation by the solid–solid reaction on the surface of Ti nanoparticles was studied in situ using a high-resolution transmission electron microscope with a heating stage. The cross-sectional image of the Ti surface was clearly observed. Vacuum-deposited carbon covered the whole the surface of Ti nanoparticles in spite of the partly evaporation on the nanoparticle surface. The diffusion of the carbon atoms inside the Ti nanoparticles depended on the size of the nanoparticles. When the Ti nanoparticle diameter was less than 30 nm, carbon atoms diffused into the Ti nanoparticle and formed TiC. The superstructure of the Ti nanoparticles was observed, which revealed the growth process of TiC to be the diffusion of carbon atoms. For Ti nanoparticles with diameter larger than 30 nm it was observed that diffusion of Ti atoms into the carbon layer was dominant, which resulted in formation of TiC in the carbon layer at the surface of Ti nanoparticles.     

Spectrophotometric determination of dopamine in microliter scale using microfluidic system based on polymeric technology

In this paper we report two simple and sensitive spectrophotometric procedures for the determination of dopamine in microfluidic system based on poly(dimethylsiloxane) (PDMS) technology and comparison of their interference-susceptibility. The analytical reactions and measurements were carried out at ambient temperature in a microreactor of total volume 6 μl coupled with a spectrophotometric flow-through cuvette.     

Intramolecular nucleophilic carbonyl trapping of alpha-ketenyl radicals by an amino group

Free-radical carbonylation of omega-alkynylamines with tributyltin hydride gives a mixture of alpha-methylene lactams and alpha-stannylmethylene lactams. Nucleophilic addition of an internal amino group to the carbonyl group of alpha-ketenyl radicals is proposed as the cyclization step. The subsequent unusual 1,4-H shift from the resulting 1-hydroxyallyl radical, followed by elimination of the beta-tributyltin radical leads to the formation of alpha-methylene lactams.     

Alloyed Tetranuclear Metal Chains of Pd4−nPtn (n=0–3) Scaffolded by a New Linear Tetraphosphine Containing a PNP Bridge

A new linear tetraphosphine containing a PNP phosphazane bridge, rac-bis[(diphenylphosphinomethyl)phenylphosphino]phenylamine (rac-dpmppan), was synthesized and utilized to support a series of Pd/Pt mixed metal tetranuclear chains, [Pd_4−nPt_n(μ-rac-dpmppan)₂(XylNC)₂](PF₆)₂ (XylNC=xylyl isocyanide; n=0: Pd₄ ( 1 ), 1: PtPd₃ ( 2 ), 2: PtPd₂Pt ( 3 ), 2: Pt₂Pd₂ ( 4 ), 3: Pt₂PdPt ( 5 )), in which the number and positions of additional Pt atoms were successfully controlled depending on the respective synthetic procedures using transformations from 1 to 3 through 2 and from 4 to 5 by redox-coupled exchange reactions. The ³¹P{¹H} NMR and ESI mass spectra and X-ray diffraction analyses revealed almost identical tetranuclear structures, with slight contraction of metal-metal bonds according to incorporation of Pt atoms. The electronic absorption spectra of 1 – 5 exhibited characteristic bands at 635–510 nm with an energy propensity depending on the number and positions of Pt centres, which were assigned to HOMO (dσ*σσ*) to LUMO (dσ*σ*σ*) transition by theoretical calculations. The present results demonstrated that the electronic structures of Pd/Pt mixed-metal tetranuclear complexes are finely tuned as orbital-overlapping alloyed metal chains by atomically precise Pt incorporation in the Pd₄ chain.     

Chiral Dinuclear EuIII,TbIII, and YIII Complexes Supported by P-Stereogenic Linear Tetraphosphine Tetraoxide

A P-stereogenic linear tetraphosphine tetraoxide, (R,R)- or (S,S)-dpmppm(=O)₄, was synthesized to prepare C₂ dinuclear M(hfa)₃ complexes (M=Eu, Tb, Y) as the first example of lanthanide(III) complexes with P-chiral multidentate phosphine oxides. The mononuclear M(hfa)₃ complexes (M=Eu, Y) with a P-chiral diphosphine dioxide, tpdpb(=O)₂, were also prepared, and comparison of their photophysical properties for the Eu^III complexes revealed that significant chiral induction from the P-chiral centers arises on the achiral M(hfa)₃ units through intramolecular π-π stacking constraint in the dinuclear system.     

Convenient synthesis of glycosyl bromide from 1-O-acetyl sugars by photo-irradiative phase-vanishing reaction of molecular bromine

The synthesis of glycosyl bromides from 1-O-acetyl sugars using a photo-irradiative phase-vanishing method involving molecular bromine was achieved. A bottom phase of molecular bromine was overlaid first with perfluorohexanes (FC-72), followed by overlaying with ethyl acetate containing a 1-O-acetyl sugar. Upon irradiation, the bromine layer gradually disappeared, leaving two phases. Glycosyl bromide was obtained in good yield from the ethyl acetate phase.     

Revisiting the Polymerization of Diphenylacetylenes with Tungsten(VI) Chloride and Tetraphenyltin: An Alternative Mechanism by a Metathesis Catalytic System

An alternative reaction mechanism of the polymerization of diphenylacetylelnes using a catalytic system composed of tungsten(VI) chloride and tetraphenyltin has been proposed through the optimization of reaction conditions and investigation of the effect of the electronic nature of diphenylacetylene monomers on the polymerizability. The detailed structures of the polymers have been suggested by mass spectrometric analysis of the obtained polymers and oligomers, which suggested that a phenyl group of tetraphenyltin has been introduced to an initiating end of the polymer chain. Mass spectrometric analysis also provided information about the termination processes of the polymerization. The experimental results strongly suggested that the polymerization of diphenylacetylenes using tungsten(VI) chloride and tetraphenyltin proceeds through a migratory insertion mechanism rather than the long‐accepted metathesis mechanism.     

Supramolecular ion channels from a transmembrane bischolic acid derivative showing two discrete conductances

Bischolic acid derivative 1 linked by m-xylylene dicarbamate at the 3,3'-position was synthesized and the single ion channel properties were examined. Compound 1 showed two clearly distinct conductances, 9.5 (type A) and 25.3 pS (type B), under 500 mM KCl symmetric salt conditions, whereas various conductances, ranging from 5-20 pS, were observed in the tetramethylether analogue reported previously. Results indicate that the replacement of four methylether groups with hydroxyls at the 7, 7', 12, and 12' positions in the bischolic acid framework influences the stability of aggregated (supramolecular) ion channel structures. Ion permeability ratios (potassium/chloride and potassium/sodium) for each type of channel were also determined.     

Carbon sources of natural cyanamide in Vicia villosa subsp. varia

The 13C labels of [13C]carbon dioxide and D-[13C?]glucose were incorporated into cyanamide (NH?CN) when they were administered to Vicia villosa subsp. varia shoots. In contrast, the administration of sodium [2,3-13C?]pyruvate did not affect the relative area of the [M + 1]+ ion of cyanamide in the gas chromatography-mass spectrometry analysis. [2,3-13C?]pyruvate was incorporated into organic acids that are part of the citric acid cycle, such as succinate and fumarate, confirming that the shoots absorbed and metabolised it. These observations demonstrated that the carbon atom of cyanamide is derived from any of the carbohydrates that are present upstream of pyruvate in the metabolic pathway.