Binding of single gold atoms on thin MgO(001) films

In the present Letter the first electron paramagnetic resonance spectra of single metal atoms on a single crystalline oxide surface are presented. For Au atoms on a MgO(001) film investigated here an analysis of the angular dependent resonance positions and the hyperfine coupling to (17)O shows that the atoms are bound on top of oxygen ions on the terrace of the film. This result is in perfect agreement with scanning tunneling microscopy measurements at 5 K presented here. The measured hyperfine matrix components allow an experimental verification of the theoretically proposed binding mechanism of Au atoms on MgO. In particular, the large reduction of the isotropic hyperfine coupling constant of supported Au as compared to free atoms is not due to a charge transfer at the interface but a hybridization of orbitals and a resulting polarization of the unpaired electron.     

A core–shell structured BaTiO3 precursor preparation,characterization and potential

A new procedure for the preparation of a core-shell-structured BaTiO(3) precursor (core=TiO(2); shell=BaCO(3)) will be described. The structure of this precursor is characterized by electron microscopy (environmental scanning electron microscopy; energy disperse X-ray spectroscopy), whereas the development of phases during thermal treatment is followed by X-ray powder diffraction.     

Synthese von Benzofulvenen und Dibenzofulvenen über 1-Chloralkyl-acetate

Synthesis of benzofulvenes and dibenzofulvenes via 1-chloroalkyl-acetates 1,2-Benzofulvene (6a) and 1,2,3,4-dibenzofulvene (7a) as well as the corresponding 6-methyl- and 6-phenyl-derivatives are prepared by reaction of sodium indenide and sodium fluorenide with 1-chloroalkyl acetates (3) , followed by elimination with KOC(CH₃)₃. The over-all yields are comparable with the results of the fulvene series and are in most cases considerably higher than the yields of the Thiele-method.     

High-pressure absorption spectroscopy in polymerizing systems

Quantitative high-pressure absorption spectroscopy in the mid infrared, near infrared, and ultraviolet region enables direct and precise investigation of high-pressure ethylene polymerizations with thermal, chemical, and laser-photochemical initiation. The special advantages of kinetic studies via quantitative near infrared spectroscopy in an extended wavenumber range are outlined. Extensions of the method on copolymer systems are indicated. The spectroscopic technique is of general applicability in studies on reactions and equilibria in dense fluid states including liquids and compressed gases.     

Telechelic Polyisobutenes with Asymmetrical Reactivity

3-Chlorocyclopentene-(1) has been used as initiator in the quasiliving cationic polymerization of isobutene. Polyisobutenes in the molecular weight range Mw = 300 - 60000 Dalton with a molecular weight distribution MWD between 1.17 and 1.34 have been synthesized. The linear polymer was selectively hydrosilated on one or both ends. With a furan coupling agent, the PIB (polyisobutene) was dimerized, yielding polymers with a cyclopentene head- and tail group.     

Chlorophosphaethenyl phosphonium ions by chloride abstraction from dichlorophosphanyl ylides

Dichlorophosphanyl ylides readily lose a chloride ion to Lewis acidic metal chlorides. In the cations so generated, a considerable part of the phosphenium charge is transferred to the phosphonium center leading to a chlorophosphaalkene structure. This is demonstrated by NMR data as well as by an X-ray structure analysis. The residual phosphenium charge becomes visible in weak but definite contacts with the GaCl⁻₄ anions that expand the coordination sphere of the P(III) atom from ψ-trigonal two-coordination to ψ-trigonal bipyramidal (ψ-TBP) tetra-coordination. © 1996 John Wiley & Sons, Inc.