57Fe Mössbauer study of FeNx (x=0.25≈0.91) alloys

⁵⁷Fe Mössbauer measurements have been perforned at the first time on iron nitrides, FeN_x(x>0.5), films prepared by rf sputtering and the measurements for γ-FeN_0.09, γ'-Fe₄N, ε-Fe_2–3N and ζ-Fe₂N have been also performed. Two new phases for x>0.5 have been identified: One has a ZnS-type structure denoted by γ" Another phase is denoted by γ''' in which iron atoms constitute a fcc lattice but the details of occupation sites of nitrogen atoms are not yet clear. The isomer shift of γ" relative to α-Fe at 300 K is rather small in comparison with that of other well known nitrides. The roam temperature Mössbauer spectra of γ''' consist of a sum of two doublets. Mössbauer spectra of γ" at 10 K do not indicate magnetically split pattern, but those of γ''' show magnetically split patterns at 10 K with the hyperfine fields of 30 T and 48 T, respectively. The component of 48 T is due to oxides, not due to nitrides.     

Synthesis of di-branched heptasaccharide by one-pot glycosylation using seven independent building blocks

[reaction: see text] We describe an efficient synthesis of di-branched heptasaccharide 1 having phytoalexin elicitor activity in soybeans by one-pot glycosylation. The synthesis involves chemo- and regioselective sequential six-step glycosylations using seven independent building blocks and sequential removal of acyl- and benzyl ether-type protecting groups. The coupling of seven building blocks requires only four chemoselective activitable leaving groups of glycosyl donors. Both the glycosylation and deprotection reactions can be achieved utilizing a parallel manual synthesizer.     

Intermolecular-medium and intramolecular-weak hydrogen bonding chains in the crystals of chiral trifluoromethylated amino alcohols

A structural feature of hydrogen bonding chains found in the crystals of trifluoromethylated amino alcohols is reported. Hydrogen bondings of 3-(N,N-dialkylamino)-1,1,1-trifluoro-2-propanols construct chiral spiral hydrogen bonding chains. Lone pairs on the nitrogen atoms of the amino alcohols participate in two hydrogen bondings. Detailed structural analysis of the hydrogen bonds of the 3-(N,N-dimethylamino)-1,1,1-trifluoro-2-propanol suggested that the chain built up with alternating intermolecular-medium and intramolecular-weak hydrogen bonds. The medium intermolecular hydrogen bond, which transfers a proton from the hydroxy group to the amino nitrogen, would make a tentative zwitterionic form of the molecule. Then, electrostatic attraction between the charges in the zwitterion centers induced a weak intramolecular hydrogen bond.     

Microchip-based immunoassay system with branching multichannels for simultaneous determination of interferon-gamma

A bead-bed immunoassay system suitable for simultaneous assay of multiple samples was constructed on a microchip. The chip had branching multichannels and four reaction and detection regions; the constructed system could process four samples at a time with only one pump unit. Interferon gamma was assayed by a 3-step sandwich immunoassay with the system coupled to a thermal lens microscope as a detector. The biases of the signal intensities obtained from each channel were within 10%, and coefficients of variation were almost the same level as the single straight channel assay. The assay time for four samples was 50 min instead of 35 min for one sample in the single-channel assay; hence higher throughput was realized with the branching structure chip.     

Palladium-catalyzed preparation of α-allyl esters and α,β-unsaturated esters from saturated esters via their silyl acetals

Reaction of ketene silyl acetals with allylic carbonates in the presence of palladium-phosphine catalyst in dioxane gives α-allyl esters in high yields. When the reaction is carried out with phosphine-free palladium catalyst in nitriles, α,β-unsaturated esters are obtained in good yields.     

Excitation-energy migration in self-assembled cyclic zinc(II)-porphyrin arrays: a close mimicry of a natural light-harvesting system

The excitation-energy-hopping (EEH) times within two-dimensional cyclic zinc(II)-porphyrin arrays 5 and 6, which were prepared by intermolecular coordination and ring-closing metathesis reaction of olefins, were deduced by modeling the EEH process based on the anisotropy depolarization as well as the exciton-exciton annihilation dynamics. Assuming the number of energy-hopping sites N = 5 and 6, the two different experimental observables, that is, anisotropy depolarization and exciton-excition annihilation times, consistently give the EEH times of 8.0 +/- 0.5 and 5.3 +/- 0.6 ps through the 1,3-phenylene linkages of 5 and 6, respectively. Accordingly, the self-assembled cyclic porphyrin arrays have proven to be well-defined two-dimensional models for natural light-harvesting complexes.