Studying Molecular Rearrangement of P1 Dye at a Passivating Alumina Surface Using Vibrational Sum-Frequency Generation Spectroscopy: Effect of Atomic-Level Roughness

The effect of roughness and thickness of alumina layers, mimicking the passivation layer commonly used in dye-sensitized photoelectrodes, on the molecular adsorption of P1 dye, 4-(bi(4-(2,2-dicyano-vinyl)-thiophene-2-yl]-phenyl]-aminobenzoic acid) has been studied using surface-sensitive vibrational sum frequency generation(VSFG) spectroscopy. The VSFG spectra reveal the formation of poorly ordered dye layers on relatively rough surfaces where XPS measures a higher dye loading. Furthermore, these poorly ordered dye molecules are responsible for the generation of trapped electronic states as probed by successive photoluminescence (PL) measurements. Surface sensitive VSFG spectroscopy in combination with XPS and PL measurements provide complementary spectral information on ordering of the adsorbed dyes, their density on the surface and electronic states of the adsorbed monolayer which are prerequisite for improving our understanding of molecularly functionalized photoelectrodes and their further development.     

First Measurement of a Thermochemical Property of a Seaborgium Compound

With only a few atoms of seaborgium (Sg, element 106), in the form of volatile SgO₂Cl₂, it was possible to determine the sublimation enthalpy of this compound using gas chromatography. Furthermore, it was demonstrated that in Group 6 Sg is chemically more similar to W than to Mo.     

Investigation of the feeding effect on the 13C/12C isotope ratio of the hormones in bovine urine using gas chromatography/combustion isotope ratio mass spectrometry

The effect of the feeding on the 13C/12C isotope ratio of four endogenous steroid hormones testosterone (T), epi-testosterone (epi-T), dehydroepiandrosterone (DHEA) and etiocholanolone (ETIO) in bovine urine was investigated. An analytical method to determine the accurate isotope ratio was developed including an extensive clean up followed by enrichment of the analytes in two steps of HPLC fractionation. Feeding experiments with four young animals were performed using C3 and C4 plants (grass, maize silage, hay, etc.) over a time period of about 280 days. One cattle was used as a control animal with no change of its diet over the full period. The detection of the 13C/12C isotope ratio of the acetylated extracts was performed by gas chromatography/combustion isotope ratio mass spectrometry. After the first change of the feeding from C4 to C3 plants significant changes of the delta 13C % values were observed from the -19 to -23% level to the -24 to -32% level for etiocholanolone and epi-testosterone in urine of three animals, whereas the DHEA values remained under the level of the two metabolites. Testosterone could not be detected with GC-C-IRMS due to its low concentration in young animals. After the second change of the diet from C3 to C4 plants (after 222 days), the measured delta 13C % values have been stabilised at the original level. The results show that in case of the feeding with only C3 plants the endogenous delta values of -32% can be reached. In this case the contribution of exogenous material with a delta value of -32% could not be detected independently of the concentration. If the diet contains C4 plants the difference or the ratio of the delta 13C % values becomes the determinant in the discriminatory power. For validation of the method a human and a cattle were treated with testosterone and the delta 13C % values were measured in incurred human and cattle urine.     

Electron beam curing of methacrylated gelatin studied by EPR and FT-Raman spectroscopy

Gelatin was modified with glycidyl methacrylate. The methacrylated gelatins were cross-linked by electron irradiation. The cross-linking process was studied by FT-Raman and EPR spectroscopy.     

Domino Reactions with Fluorinated Five-membered Heterocycles – Syntheses of Trifluoromethyl Substituted Butenolides and γ-Ketoacids

A new approach to trifluoromethyl substituted butenolides and their thioanalogues is described starting from 2-fluoro-3-trifluoromethylfurans and -thiophenes, respectively. The reaction sequence includes three steps – nucleophilic displacement reaction, Claisen, and finally Cope rearrangement – which can be run as domino reaction. A modification of the domino reaction (transesterification instead of Cope rearrangement) provides a concise access to α-trifluoromethyl-γ-ketoacids.     

A convenient method for the synthesis of 2-amino substituted aza-heterocycles from N,N′-disubstituted thioureas using TsCl/NaOH

p-Toluenesulfonyl chloride (TsCl)/NaOH has been introduced as reagent combination for the synthesis of 2-amino-oxa- or 2-amino-thiazolidines from N-(2-hydroxyethyl)-thioureas, but its general application in heterocycle synthesis has not been investigated. In this paper the convenient and efficient synthesis of a variety of 2-amino-substituted 1-aza 3-(aza, oxo or thio) heterocycles of different substitution and ring sizes is described. The application of polymer-supported TsCl facilitates work-up and renders the reaction conditions very suitable for parallel or robot synthesis.