Supramolecular phthalocyanine dimers based on the secondary dialkylammonium cation/dibenzo-24-crown-8 recognition motif

[formula: see text] New unsymmetrically substituted DB24C8-phthalocyanines, which are able to form complexes with suitable dialkylammonium cations, have been prepared. These complexes most probably have a pseudorotaxane geometry.     

Untersuchungen an oxidischen Katalysatoren. XXXV. Redoxverhalten des Nickels in NiNaY-Zeolithen 2. Untersuchungen zur Dispersität von Ni- und Ni/NiO-Teilchen in reduzierten und reoxydierten NiNaY-Proben

Studies on Oxide Catalysts. XXXV. Redoxbehaviour of Nickel in Zeolite NiNaY. 2. Investigation on the Dispersion of Ni- und Ni/NiO-Species in Reduced and Reoxidized NiNaY Samples Oxygen chemisorption and electronmicroscopic measurements (ultramicrotome technique) correspondingly show a decrease of the metal dispersion with increasing reduction temperature (470–870 K) and exchange degree (10, 29, 54 equ.-% resp.). Contrary to this results electronmicroscopic measurements with replica technique don't reflect such a dependence. Increase of particle size after reoxidation (470 K) and reduction at 470 to 870 K (regeneration) of the NiNaY samples are attributed on the one hand to the aggregation of oxidic particles and on the other hand to metal sintering by the subsequent reduction step. A decrease of dispersion after a reoxidation process at 670 K is caused by formation and relocalisation of isolated nickel ions.     

Untersuchungen an oxidischen Katalysatoren. XLII. Redoxverhalten des Nickels in NiNa?Y-Zeolithen 4. Einfluß der Zusammensetzung auf die Reduzierbarkeit von Nickel in NiNa?Y-Zeolithen

Studies on Oxide Catalysts. XLii. Redox Behaviour of Nickel in Zeolites NiNa? Y. 4. Influence of Composition on the Reducibility of Nickel in Zeolites NiNa? Y By chemical analysis (reaction with K₂Cr₂O₇) and ESCA investigations we determined the degree of reduction in reduced samples NiNa-Y as function of the mole ratio SiO₂/Al₂O₃ (module), of the Ni²⁺ degree of exchange and the kind of the second cations. (NH₄₊, Ca²+, Co²+, and Nd³+) in the temperature region of 620–770 K. The degree of nickel reduction increases with increasing module, decreasing degree of exchange and decreasing number of Brönsted acidic centres. This behaviour is caused by the influence of the interaction between cations Ni²⁺ and zeolite lattice on the reduction equilibrium.     

Synthesis and characterization of novel carbene complexes of phosphorus(V) fluorides with potential liquid-crystalline properties

A series of novel push–pushI and push–pullII carbene-stabilized complexes of phosphorus(V) fluorides bearing substituents with liquid-crystalline properties were synthesized by the oxidative addition of difluoroamines to phosphorus(III) halides. These octahedral complexes were characterized by NMR spectroscopy and X-ray analysis.     

Incomplete relaxation and plasmon formation in the K emission band of copper

A method of calculating the effect of self-absorption in X-ray emission spectra and which is suitable for non-adiabatic excitation processes is presented. The Fermi-level E_F and the “true” profile of the electron-excited (20–40keV) CuKβ_2,5 band are determined. A deviation from the calvulated one-electron spectrum in the energy interval [-12 eV, -7 eV] below E_F is interpreted as a result of plasmon formation and Auger broadening. A pronounced disagreement is found also in the range [-1 eV, + 10eV]. Above E_F, a part of the intensity may be due to incomplete electron relaxation.     

Low temperature scanning force microscopy of the Si(111)-(7x7) surface

A low temperature scanning force microscope (SFM) operating in a dynamic mode in ultrahigh vacuum was used to study the Si(111)- (7x7) surface at 7.2 K. Not only the twelve adatoms but also the six rest atoms of the unit cell are clearly resolved for the first time with SFM. In addition, the first measurements of the short range chemical bonding forces above specific atomic sites are presented. The data are in good agreement with first principles computations and indicate that the nearest atoms in the tip and sample relax significantly when the tip is within a few A of the surface.