S(IV) induced autoxidation of Cu(II)/tetraglycine complexes in the presence of aldehydes: mechanistic considerations and analytical applications

An indirect amperometric method for the determination of sulfite in a flow injection configuration is described. The procedure is based on the amperometric measurement (E=0.1 V) of Cu(III) chemically generated by the S(IV) induced oxidation of Cu(II)/tetraglycine by dissolved oxygen. The dynamic analytical range was 5-100 muM with a detection limit of 1 muM. The repeatability for the determination (10 muM) was evaluated to be 1.4% (n=20). The method was employed for the determination of S(IV) in wine after its extraction from acidified samples by bubbling argon and the results were in agreement with those obtained by the iodometric procedure. The influence of formaldehyde and acetaldehyde on the Cu(III) formation is also discussed on the basis of the mechanism of the induced reaction.     

Surface modification of metallic Co nanoparticles

Monodisperse Co nanoparticles were synthesized by thermal decomposition in the presence of aluminium alkyls yielding air-stable Co nanoparticles after surface passivation. Several procedures for surface modification of these pre-stabilized, metallic Co nanoparticles are presented, including direct anchoring of surface-active functional groups and biocompatible dextran layers as well as silica and polymer coatings. As a result, individually coated nanoparticles as well as microspheres can be obtained.     

Fluorometric and NMR Studies of the Naproxen–Cyclodextrin Inclusion Complexes in Aqueous Solutions

Inclusion complexation processesinvolving four cyclodextrins and naproxen have beenstudied for the protonated and unprotonated forms ofthe guest molecule. The association constants havebeen evaluated from changes in the fluorescenceintensity of naproxen following addition of acyclodextrin to an aqueous naproxen solution. ¹HNMR NOESY and ROESY spectra have shown that twoorientations of the guest molecule relative to-cyclodextrin are possible.     

Alkylation of schleyer's lithiocarbon C4Li4 by methyl iodide

Alkylation of lithiocarbon C₄Li₄ gives the hydrocarbon C₈H₁₂ to which the structure of tetramethyltetrahedrane has been ascribed.     

A simple and fast procedure for efficient synthesis of β- and γ-azidoarylketones

A simple and efficient method for preparing β- and γ-azido substituted arylketones has been achieved by short microwave irradiation of the corresponding halo arylketones and sodium azide in DMSO.     

Absolute stereochemistry of allylic alcohols,amines, and other ene moieties: a microscale cross metathesis/exciton chirality protocol

A microscale chemical/chiroptical protocol for the determination of absolute configurations of allylic alcohols, amines, and related systems has been developed. The method is based on the conversion of the double bonds into a styrene, lambdamax 248 nm (epsilon 15 000), or other styrenoid chromophores by cross olefin metathesis. The obtained styrenoid chromophore then couples with the allylic acylate to yield a distinct couplet. The proposed method allows one to determine the absolute configuration of both moieties flanking the double bond. It also overcomes the restriction of the conventional allylic benzoate method that gives rise to weak CD couplet, for which in many cases only one wing of the couplet is observable.     

Resonant second-order nonlinear optical processes in quantum cascade lasers

We demonstrate an efficient intracavity nonlinear interaction of laser modes in a specially adapted quantum cascade laser. A two-wavelength quantum cascade laser structure emitting at wavelengths of 7.1 and 9.5 micrometer included cascaded resonant optical intersubband transitions in an intracavity configuration leading to resonantly enhanced sum-frequency and second-harmonic generation at wavelengths of 4.1, 3.6, and 4.7 micrometer respectively. Laser peak optical powers of 60 and 80 mW resulted in 30 nW of sum-frequency signal and 10-15 nW of second-harmonic signal, both in good agreement with theoretical calculations.