Deposition of molecular probes in heavy ion tracks

By using polarized fluorescence techniques the physical properties of heavy ion tracks such as the dielectric number, molecular alignment and track radius can be traced by molecular fluorescence probes. Foils of poly(ethylene terephthalate) (PET) were used as a matrix for the ion tracks wherein fluorescence probes such as aminostyryl-derivatives can be incorporated using a suitable solvent, e.g. N,N′-dimethylformamide (DMF) as transport medium. The high sensitivity of fluorescence methods allowed the comparison of the probe properties in ion tracks with the virgin material. From the fluorescence Stokes shift the dielectric constants could be calculated, describing the dielectric surroundings of the molecular probes. The lower dielectric constant in the tracks gives clear evidence that there is no higher accomodation of the highly polar solvent DMF in the tracks compared with the virgin material. Otherwise the dielectric constant in the tracks should be higher than in the virgin material. The orientation of the molecular probes was examined by polarized fluorescence spectroscopy. It is shown that deposited molecular probes witha high aspect ratio have a preferential orientation parallel to the ion track axis.     

Combinatorial Criteria for Ramifiable Ordered Sets

The tree‐property (classica in cardina theory) and its variants make sense also for directed sets and even for partially ordered sets. A combinatoria approach is developed here, with characterizations and criteria involving (inter alia) adequate families of special substructures of directed sets. These substructures form a natural hierarchy that is also investigated.     

Calorimetrie

Ohne Zusammenfassung     

Syntheses and X‐Ray Structures of μ‐Carbamoyl Complexes of Iron; Isomers of [(CO)3Fe(μ‐Me2NCO)2Fe(CO)2(NHMe2)] with Symmetrical and Asymmetrical Intramolecular NH···O Contacts

Reaction of the carbamoyl complex [C(NMe₂)₃][(CO)₄FeC(O)NMe₂] ( 1 ) with silver salts gives the dinuclear μ‐carbamoyl complex [(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)₂(HNMe₂)] ( 2 ). Depending on the solvent, crystals of 2a with an asymmetrical or of 2b with a symmetrical internal NH···O bridge are formed. The dimethylamino group is originated from a further molecule of 1 from which an amino group is transferred to the “α‐CO” ligand of an intermediate oxidation product while the H⁺ ion probably comes from deprotonation of a guanidinium cation. The HNMe₂ ligand cannot be replaced by CO but easily by PPh₃ to give [(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)₂(PPh₃)] ( 3 ). All complexes were studied by X‐ray diffraction analyses and the usual spectroscopic methods.