Hexaaminobenzene derivatives: synthesis and unusual oxidation behavior

The syntheses and the electrochemical behavior of the monomeric peralkylated hexaamino(1,3)metacyclophane 4, the dimeric dodecaamino(1,3)cyclophane 5a, and the dodecaamino(1,3,5)cyclophane 6 are described. Electrochemical measurements show that the hexaaminobenzene units in 4 and 5a undergo an unusually slow two-electron transfer attributed to the deformation of the rings into bis-cyanine cations when oxidized to the respective dication. Further oxidations to tri-, tetra-, and hexacationic units occur at more positive potentials. In the dimeric structures, no interaction between the rings can be seen in the (1,3)cyclophane, but strong interaction for the (1,3,5)cyclophane is observed.     

Induced changes in stimulated Raman scattering intensities

The stimulated Raman scattering (SRS) intensity of neat liquids and of binary liquid mixtures was measured as a function of the power of the pump field and of an additional radiation field at the Stokes frequency. In neat p-xylene SRS intensity transfer, form one vibrational mode to another, was observed. In benzene/nitrobenzene mixtures it was found possible, at various concentrations, to selectively generate SRS from one component in the mixture, including the minor one. Implications of the results for the selective excitation by the SRS process of a single species in a mixture are discussed.     

Laser flash spectroscopy of iodine and iodoform

The absorption spectra and decay times of transient species produced by laser flash photolysis of iodine and iodoform solutions are reported. The results show that the primary process in the photolysis of iodoform is the formation of atomic iodine.     

Drug targeting by drug entrapment into ultrafine compartments as carriers

The incorporation of drugs into vesicles is one of several technological methods for the optimization of targeted drug delivery and controlled drug targeting. The main problems will always remain

? To design inert auxiliary accompanying materials in order to overcome side reactions

? To use body-friendly and biodegradable macromolecular carrier materials for the therapeutic system

? To miniaturize the dosage form dramatically in the submicroscopic size range in order to eliminate foreign body irritations

? To develop ultrafine solid and amorphous vesicular compartments (nanocapsules, nanopellets, nanoparticles) to get stable systems with good tissue transfer and organ targeting properties

The actual stand of the incorporation of drugs and biologic active material into ultrafine colloidal solid capsules is reviewed here as for instance:

? Immunoactive material

? Fluorescent indicators in body fluids

? Controlled and sustained release systems

? Nonspecific drug targeting of the first-order (passage through endothelial tissues)

? Second-order targeting (a specific transparenchymal migration), and a highly specific targeting of the third-order (transcellular passage, especially lysosomal transports)

Examples for some of these applications are given. It can be shown that such ultrafine vesiculated capsules offer some advantages when applied parenterally, but also partly for oral application. In the future, still more studies are necessary finally to clarify the importance and practical use of such ultrafine targeting carriers.     

Electron-Deficient Imidazolium Substituted Cp Ligands and their Ru Complexes

The synthesis of electron-poor mono-, di- and tri(imidazolium)-substituted Cp-ylides is presented and their electronic properties are discussed based on NMR spectroscopy, X-ray structure analyses, electrochemical investigations and DFT calculations as well as by their reactivity toward [Ru(CH₃CN)₃Cp*](PF₆). With mono- and di(imidazolium)-substituted cyclopentadienides the respective monocationic and dicationic ruthenocences are formed (X-ray), whereas tri(imidazolium) cyclopentadienides are too electron-poor to form the ruthenocenes. Cyclic voltammetric analysis of the ruthenocenes shows reversible oxidation at a potential that increases with every additional electron-withdrawing imidazolium substituent at the Cp ligand by 0.53–0.55 V in an electrolyte based on a weakly coordinating anion. A reversible oxidation can be observed for the free 1,3-disubstituted ligand as well.     

Probleme aus dem Gebiet der ganzen transzendenten Funktionen

Ohne Zusammenfassung