Bis- and tetrakis(organosilyl) decatungstosilicate,

The high propensity of organosilanes towards polycondensation and reaction with nucleophilic moieties has facilitated the formation of new organic-inorganic hybrids based on the lacunary divacant heteropolyanion [gamma-SiW10O36]8-. Depending on the experimental conditions two different types of derivatives were obtained with the general formula [gamma-SiW10O36(RSi)2O]4- (1) (>90% yield) and [gamma-SiW10O36(RSiO)4]4- (2) (>85% yield) (R = H (1a, 2a), vinyl (1b), -C3H6OC(O)C-(Me)=CH2 (1c, 2c), phenyl (1d, 2d)). The structures of the hybrid anions have been inferred from spectroscopic data, in particular from multinuclear (29Si and 183W) NMR solution studies and from MALDI-TOF mass spectrometry. Both species correspond to the grafting of an oxo-bridged siloxane unit onto the surface of the lacunary polyoxoanion.     

The structure of higher order C60-fullerene-γ-cyclodextrin complexes

C₆₀ inclusion complexes in γ-cyclodextrin are studied by molecular mechanics and semi-empirical methods with the aim of comparing measured and calculated induced circular dichroism (ICD) spectra. Low energy geometries of the complexes are generated by Monte Carlo simulations, also accounting for solvation effects by an aqueous environment. The ICD spectrum of the complex is then obtained from an exciton model based on semi-empirical calculations of the transition energies and the corresponding transition moments. Highly symmetric, tightly bound complexes of two γ-cyclodextrins and buckminsterfullerene are found as the most probable structures. The main bands of the experimentally derived ICD spectrum are assigned to the excitation transitions of the chromophore and are discussed in comparison to calculations on the magnetic circular dichroism (MCD) spectrum of C₆₀.     

Influence d'un fort champ electrique statique sur le spectre d'absorption du polyester mylar

Electrical fields induce a shift towards lower frequencies of the absorption spectrum of mylar, this shift, proportional to the square of the field, is three orders of magnitude smaller than a typical Franz-Keldysh effect and is sensitive to the relative orientation of the static field with respect to the polarization vector of the light. We suggest that the measured shift is mostly due to Stark effects in this amorphous material. This kind of measurement could be used to estimate the degree of crystalline order in partially amorphous solids.     

Synthese von optisch aktiven,natürlichen Carotinoiden und strukturell verwandten Verbindungen. III. Synthese von (+)-Abscisinsäure, (−)-Xanthoxin, (−)-Loliolid, (−)-Actinidiolid und (−)-Dihydroactinidiolid

Synthesis of optically active natural carotenoids and structurally related compounds. III. Synthesis of (+)-abscisic acid, (?)-xanthoxin, (?)-loliolide, (?)-actinidiolide, and (?)-dihydroactinidiolide The syntheses of (+)-abscisic acid ( 1 ), (?)-xanthoxin ( 2 ), (?)-loliolide ( 3 ), (?)-actinidiolide ( 4 ), and of (?)-dihydroactinidiolide ( 5 ) from one common starting material are reported. The syntheses yield also some enantiomeric or diastereomeric analogues.     

Einfluß der Donoreigenschaften organischer Lösungsmittel auf die Ionisation von Tritylhalogeniden

Zusammenfassung Die Ionisation vonPh ₃CCl undPh ₃CBr durch aprotische Donoren wurde in Nitrobenzol mit Hilfe von Leitfähigkeitsmessungen untersucht. Das Ausmaß der Ionisation ist proportional den Donizitäten. Ausnahmen werden auf sterische Hinderung zurückgeführt. Die Verbindung [Ph ₃C·py]⁺Br^– wurde isoliert.

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Influence of the donicity of organic solvents on the ionization of triphenylhalomethanes

The ionization ofPh ₃CCl andPh ₃CBr by aprotic donors was studied conductometrically in nitrobenzene solution. The degree of ionization increases with increasing donicity of the donor except when sterical hindrance is operative. The compound [Ph ₃C·py]⁺Br^– was isolated.

     

Electron hole condensate radiation from Ge double injection devices between 1.5° and 4.2°

Carrier injection in Ge at helium temperatures produces radiation characteristic of the electron hole condensate. Time resolved spectra are used to analyze the presence of both condensate and free exciton radiation at high power levels. Device heating is indicated.