Angle-resolved photoemission of the c(2 × 2) and c(3 × 1) oxygen overlayers on Fe(110)

Angle-resolved photoemission spectroscopy utilizing synchrotron radiation has been used to study the band structure of the c(2×2) and (3×1) oxygen overlayers on Fe(110). The symmetries of the O-2p-derived states at the center of the surface Brillouin zone $\text{(}\text{Γ}\text{)}$ were identified using polarized light. At $\text{Γ}$ the p_xp_y- and p_z-derived levels are at about 5.5 and 7.0 eV below the Fermi level, respectively, for both ordered overlayers. The p-states of the c(2×2)-O structure show very little dispersion (?0.1 eV) with $\text{k}{}_{\mathrm{}}$. On the other hand, the c(3×1)-O overlayer exhibits considerable dispersion of ～1.6 eV. The essential features of the measured dispersion are reproduced well by the dispersion predicted in a qualitative way for an isolated c(3×1) oxygen monolayer.     

Nuclear magnetic resonance studies on microstructure of ethylene copolymers. VII. Proton resonance spectra of hydrolyzed ethylene–vinyl acetate copolymers1

Complete and partial alcoholyses of ethylene–vinyl acetate (E–VA) copolymers yield ethylene–vinyl alcohol (E–VOH) copolymers and ethylene–vinyl acetate–vinyl alcohol (E–VA–VOH) terpolymers, respectively. From the 220-MHz proton NMR spectra of E–VOH copolymers the stereoregular and chemical sequence distributions of the comonomers can be readily determined. Partially hydrolyzed E–VA polymers were acetylated with perdeuterated acetic anhydride. The monomer distributions in the terpolymers were then quantitatively determined by examining the proton spectra of the derived products. It was found that alcoholysis of E–VA polymers occurs preferentially at VA units which have neighboring VA groups.     

Fluorescent products of the reaction of mono-substituted guanidino compounds with benzoin-dimethylformamide

The fluorescent products formed from methylguanidine or phenylguanidine and benzoin in the presence of dimethylformamide are shown to be the corresponding 2-substituted amino-4, 5-diphenylimidazoles. They fluoresce most intensely at pH 9–10 and the fluorescence is stabilized by β-mercaptoethanol.     

Calculation of the electronic structure of ethylene by the SCF-Xα scattered wave method

The electronic structure of ethylene is investigated by the implementation of the Xα scattered wave method and a comparison is made with SCF LCAO results. Calculations are also carried out for different geometrical configurations of the molecule, in which one HCH plane is rotated through different angles relative to the other.     

Synthesis and characterization of nickel(II) complexes with potentially pentadentate macrocyclic ligands having N3O2 donor set

Nickel(II) complexes of N₃O₂ donor macrocycles incorporating 17- to 19-membered macrocyclic rings have been prepared. Physical measurements ind     

Rhenium carbonyl complexes with monodentate-coordinated diphosphines: activation of terminal phosphino groups towards amine-oxide oxidation

Terminal phosphino groups of [Re₂(CO)₉(η¹-P-P)] (P-P = diphosphines) are activated towards oxidation by Me₃NO. The respective reactions of Me₃NO with [Re₂(CO)₉{η¹-P(o-anisyl)₂(CH₂)₃PPh₂}], [Re₂(CO)₉{η¹-PPh₂(CH₂)₃P(o-anisyl)₂}] and [Re₂(CO)₉(η¹-trans-PPh₂CHCHPPh₂)] were studied to investigate the mechanism of this oxidation. The results are consistent with an intramolecular pathway involving a cyclic intermediate, without exchange of the coordinated and terminal phosphino groups. A mechanism which involves an interaction of the terminal phosphino group with a carbonyl ligand is proposed. In sharp contrast to eq-[Re₂(CO)₉(η¹-P-P)] (P-P = Ph₂P(CH₂)_nPPh₂, n = 1-6), eq-[Re₂(CO)₉(η¹-trans-PPh₂CHCHPPh₂)] appears to be indefinitely stable towards equatorial → axial isomerization at room temperature, thus, allowing its crystal structure to be determined.     

Preparation of new bis(oxazoline) ligand bearing non-covalent interaction sites and an application in the highly asymmetric Diels-Alder reaction

New asymmetric bis(oxazoline) (Box) ligand bearing amide group at the oxazoline 4-position, (S,S)-2,2′-methylenebis(4-tert-butylcarbamoyl-2-oxazoline) (1S), was designed and synthesized for selective catalytic reaction. The crystal structure of the ternary copper complex, consisting of 1S and N-benzoyl-N-phenyl-hydroxylamine, demonstrated interligand interactions, such as hydrogen bonding and CH-π interaction. Catalytic performance of the copper complex with 1S was investigated for an asymmetric Diels-Alder reaction using benzylidene-2-acetylpyridine and 1,3-cyclohexadiene (CHD). The reaction product was enantio-pure endo-(pyridin-2-yl)(3-phenylbicyclo[2,2,2]oct-5-ene-2-yl)methanone (BPCD), of which crystal structure was analyzed by the X-ray method. No stereo- and enantio-isomer of BPCD was detected by chiral HPLC analysis. Introduction of hydrogen bonding site into 1S can promote the Diels-Alder reaction even though using poor reactive CHD. Without 1S, this reaction did not give any product. Addition of 2-propanol to this reaction system inhibited the formation of BPCD, indicating that the designed interligand interaction sites, especially hydrogen bonding, play an important role for catalytic performance.     

FT-IR study of the interlamellar water confined in glycolipid nanotube walls

The local hydrogen-bonding environment of water confined in glycolipid nanotubes (LNTs) was investigated by Fourier transform infrared (FT-IR) spectroscopy. Using X-ray diffraction (XRD), we estimated the thickness of an interlamellar water layer, which was confined between the bilayer membranes constructing the walls of the LNTs, to be 1.3 +/- 0.3 nm. FT-IR spectroscopic measurement of the confined water showed an obvious reduction in IR absorption in both the low-energy (around 3000 cm(-1)) and high-energy regions (around 3600 cm(-1)) of the OH stretching band as compared to bulk water. The reduction around 3000 cm(-1) indicated a decrease in the relative proportion of the water molecules with a long-range network structure due to a geometrical restriction. This agrees with the results obtained for other multilamellar systems. On the other hand, the remarkable reduction around 3600 cm(-1), which was not observed in the other systems, indicated the absence of weakly hydrogen-bonded water aggregates due to the effect of sugar headgroups.