Synthesis and Host-abilities of some New Corands Bearing Uncommon Chiral Spacer Units

Benzo- and naphtho-ethylene glycols are prepared from dihydroxy-benzenes or -naphthalenes and the corresponding chloroethoxyethanols using known procedures. Cyclocondensation reactions of these open-chain diols with the chiral and concave tetra-t-butyl-2,6,9-trioxabicyclo[3.3.1]nonadiene (“bridged bisdioxine”) bisacid chloride afford several new corands. In one case, besides the expected macrocycle, an open-chain podand is obtained and further cyclized to a large 2:2 macrocycle. The bridged bisdioxine spacer may also be converted into the tetraoxaadamantane scaffold as shown with an example. Extraction experiments employing selected corands towards various metal ions show a significant host-property towards Hg(II) salts for those macrocycles having o-disubstituted aryl groups incorporated, thus forming 1:1 complexes. NMR titration studies with sodium thiocyanate as well as with some organic guests do not exhibit significant host–guest interactions, in the case of Hg(II) thiocyanate a weak complexation was determined.     

Techniques for measuring the elastic wave velocities of melts and partial molten systems under high pressure conditions

The Earth's deep interior is accessible only by indirect methods, first and foremost seismological studies. The interpretation of these seismic data and the corresponding numerical modelling require measurements of the elastic properties of representative Earth materials under experimental simulated in situ pressure-temperature conditions. Various experimental techniques for velocity measurements under crustal and mantle conditions and the results are described.     

Zur Extraktion von Cu(II) mit α-Dioximen

Es wird über die Extraktion von Cu(II) mit Pentan-2,3-diondioxim und Oktan-2,3-diondioxim aus nitrathaltiger wäßriger Lösung berichtet. Die untersuchten Extraktionsgleichgewichte werden diskutiert.     

Ultrafast Photodynamics of the Indoline Dye D149 Adsorbed to Porous ZnO in Dye‐Sensitized Solar Cells

We investigate the ultrafast dynamics of the photoinduced electron transfer between surface‐adsorbed indoline D149 dye and porous ZnO as used in the working electrodes of dye‐sensitized solar cells. Transient absorption spectroscopy was conducted on the dye in solution, on solid state samples and for the latter in contact to a I^?/I₃^? redox electrolyte typical for dye‐sensitized solar cells to elucidate the effect of each component in the observed dynamics. D149 in a solution of 1:1 acetonitrile and tert‐butyl alcohol shows excited‐state lifetimes of 300±50 ps. This signature is severely quenched when D149 is adsorbed to ZnO, with the fastest component of the decay trace measured at 150±20 fs due to the charge‐transfer mechanism. Absorption bands of the oxidized dye molecule were investigated to determine regeneration times which are in excess of 1 ns. The addition of the redox electrolyte to the system results in faster regeneration times, of the order of 1 ns.     

Investigation of magnetic active core sizes and hydrodynamic diameters of a magnetically fractionated ferrofluid

In this work we address the question which relates between the size of the magnetically active core of magnetic nanoparticles (MNPs) and the size of the overall particle in the solution (the so-called hydrodynamic diameter d _hyd) exists. For this purpose we use two methods of examination that can deliver conclusions about the properties of MNP which are not accessible with normal microscopy. On the one hand, we use temperature dependent magnetorelaxation (TMRX) method, which enables direct access to the energy barrier distribution and by using additional hysteresis loop measurements can provide details about the size of the magnetically active cores. On the other hand, to determine the size of the overall particle in the solution, we use the magnetooptical relaxation of ferrofluids (MORFF) method, where the stimulation is done magnetically while the reading of the relaxation signal, however, is done optically. As a basis for the examinations in this work we use a ferrofluid that was developed for medicinal purposes and which has been fractioned magnetically to obtain differently sized fractions of MNPs. The two values obtained through these methods for each fraction shows the success in fractioning the original solution. Therefore, one can conclude a direct correlation between the size of the magnetically active core and the size of the complete particle in the solution from the experimental results. To calculate the size of the magnetically active core we found a temperature dependent anisotropy constant which was taken into account for the calculations. Furthermore, we found relaxation signals at 18 K for all fractions in these TMRX measurements, which have their origin in other magnetic effects than the Néel relaxation.     

Recent advances in sulfoxidation reactions: a metal-free approach

Through the oxidation of sulfides useful elements of stereocontrol in asymmetric synthesis and important targets of pharmaceutical interest can be obtained. A number of metal-free methods have been developed over recent years for sulfoxidation reactions. The results published after 1998 through the beginning of 2010 have been reviewed with a focus being placed on sulfoxidations with hypervalent iodine compounds; iminium- and oxaziridinium derivatives; organic hydroperoxides and organocatalysts. In addition, autocatalytic and catalyst-free variants are discussed. Although, the asymmetric organocatalytic sulfoxidation is still in its infancy, the reported results show the high potential and versatility of this metal-free methodology.