On finite intersections of “henselian valued” fields

In this note we study finite intersections of henselian valued fields, i.e. fields carrying either a henselian valuation ring or a henselian absolute value which is (real-) archimedean. To be more precise, we intersect a finite number of henselian valued respectively real closed fields such that the induced valuation rings respectively orderings generate different V-topologies on the intersection, and investigate its algebraic and valuation-theoretic properties.     

Ermittlung optimaler Meßbedingungen für die atomabsorptions-spektroskopische Bestimmung von Edelmetallen

The parameters for the determination of noble metals by atomic absorption technique are optimized by minimizing of the coeffizients of variation. The optimal conditions for the determination of the elements Ag, Au, Ir, Pd, Pt, Rh and Ru are given.     

Stereospecific capillary electrophoresis assays using pentapeptide substrates for the study of Aspergillus nidulans methionine sulfoxide reductase A and mutant enzymes

Stereospecific capillary electrophoresis‐based methods for the analysis of methionine sulfoxide [Met(O)]‐containing pentapeptides were developed in order to investigate the reduction of Met(O)‐containing peptide substrates by recombinant Aspergillus nidulans methionine sulfoxide reductase A (MsrA) as well as enzymes carrying mutations in position Glu99 and Asp134. The separation of the diastereomers of the N‐acetylated, C‐terminally 2,4‐dinitrophenyl (Dnp)‐labeled pentapeptides ac‐Lys‐Phe‐Met(O)‐Lys‐Lys‐Dnp, ac‐Lys‐Asp‐Met(O)‐Asn‐Lys‐Dnp and ac‐Lys‐Asn‐Met(O)‐Asp‐Lys‐Dnp was achieved in 50 mM Tris‐HCl buffers containing sulfated β‐CD in fused‐silica capillaries, while the diastereomer separation of ac‐Lys‐Asp‐Met(O)‐Asp‐Lys‐Dnp was achieved by sulfated β‐CD‐mediated MEKC. The methods were validated with regard to range, linearity, accuracy, limits of detection and quantitation as well as precision. Subsequently, the substrates were incubated with wild‐type MsrA and three mutants in the presence of dithiothreitol as reductant. Wild‐type MsrA displayed the highest activity towards all substrates compared to the mutants. Substitution of Glu99 by Gln resulted in the mutant with the lowest activity towards all substrates except for ac‐Lys‐Asn‐Met(O)‐Asp‐Lys‐Dnp, while replacement Asn for Asp134 lead to a higher activity towards ac‐Lys‐Asp‐Met(O)‐Asn‐Lys‐Dnp compared with the Glu99 mutant. The mutant with Glu instead of Asp134 was the most active among the mutant enzymes. Molecular modeling indicated that the conserved Glu99 residue is buried in the Met‐S‐(O) groove, which might contribute to the correct placing of substrates and, consequently, to the catalytic activity of MsrA, while Asp134 did not form hydrogen bonds with the substrates but only within the enzyme.     

Intramolecular Reactivity of π-Coordinated P-Heterocycles: How to Form Five-Membered Rings out of Phosphaalkynes

Experimental and theoretical evidence is presented for a novel metal-dependent intramolecular reactivity of ~ -bonded, unsaturated P-heterocycles like 1,3-diphosphete and 1,3,5-triphosphinine. The nucleophilic attack of a P lone pair of 1,3-diphosphete toward a neighboring ligand leads to new bicyclic ligands with unique structural features. A metal-initiated intramolecular hydrogen transfer and C--C bond formation are observed for (1,3,5-triphosphinine)(COD)Fe to result in the formation of [(CO) 5 Cr(4,5,6-trihydro-1,3,5-triphosphinine)(trihydropentalene)Fe].     

Structural chemistry of polycyclic heteroaromatic compounds. Part XI. Photoelectron spectra and electronic structures of tetracyclic hetarenes of the triphenylene type

The UV photoelectron spectra of several tetracyclic heteroaromatic compounds (2-9) which are pi-isoelectronic with triphenylene (1) have been recorded and analysed making use of semiempirical AM1 and PM3 as well as ab initio/DFT B3LYP calculations. In one series of compounds (2-7), the peripheral benzene rings of 1 are successively substituted by thiophene rings that are either [b]- or [c]-annellated with the central benzene unit. In 2-7 only marginal shifts are found for most of the IPs of electrons. In the benzotrithiophenes 5-7, a systematic variation is displayed by IP(pi7). Compared to 1, the pi electron system of benzo[c]trithiophene (7) is approximately two times as much destabilized as in the isomers 5 and 6 with [b]annellated thiophene rings. The IP[n(S)] values of the thiophene derivatives 2-7 indicate that these orbitals are clearly destabilized relative to thiophene. The same holds for the n(O) orbital of the furane derivative 9 in comparison with that of furane. In 9, only the higher pi MOs (pi7-pi9) are destabilized whereas the lower levels (pi1-pi4) are stabilized, and those in between (pi5-pi6) remain essentially unshifted. In the pyrrole derivative 8, all pi MOs are substantially destabilized by about 0.5-1.6 eV relative to 1.     

Dynamic Phenomena in Self‐Complementary {2}‐Metallocryptates Probed by Solution 133Cs‐NMR. New Insights into Ion Pairing Processes: X‐Ray Structure and Solid‐State NMR Spectra of a Meandering Species

Two self‐complementary {2}‐metallocryptates, differing in methyl and phenyl substituents, respectively, have been studied by X‐ray analysis, and solid‐state and solution NMR. Mixed Mg/Cs metal methyl complex 2 is a linear polymer in the solid state. The two different Cs sites are confirmed by ¹³³Cs‐solid‐state NMR. By contrast, the analog mixed Mg/Cs metal phenyl complex 4 is a meandering polymer as shown by an actual X‐ray analysis. The four non‐equivalent Cs‐sites in 4 are reflected in the solid‐state NMR spectra. Solution ¹³³Cs‐NMR spectra of 4 reveal two independent dynamic processes: a fast exchange of Cs within contact ion‐pairs and solvent‐separated ion‐pairs (CIP, SSIP), and a slower exchange of ‘inside’ endo Cs, surrounded by three ligands, and ‘outside’ exo Cs involved in the CIP/SSIP equilibrium. Complete line‐shape analysis of variable‐temperature ¹³³Cs‐NMR spectra of 4 yield kinetic parameters of =10.8 kcal/mol for the fast SSIP‐CIP exchange and =13.2 kcal/mol for the slower endo/exo exchange of Cs. DOSY‐NMR Measurements confirm the monomeric nature of 4 in solution.     

Observation of the inverse trans influence (ITI) in a uranium(V) imide coordination complex: an experimental study and theoretical evaluation

An inverse trans influence has been observed in a high-valent U(V) imide complex, [(((Ad)ArO)(3)N)U(NMes)]. A thorough theoretical evaluation has been employed in order to corroborate the ITI in this unusual complex. Computations on the target complex, [(((Ad)ArO)(3)N)U(NMes)], and the model complexes [(((Me)ArO)(3)N)U(NMes)] and [(NMe(3))(OMe(2))(OMe)(3)U(NPh)] are discussed along with synthetic details and supporting spectroscopic data. Additionally, the syntheses and full characterization data of the related U(V) trimethylsilylimide complex [(((Ad)ArO)(3)N)U(NTMS)] and U(IV) azide complex [(((Ad)ArO)(3)N)U(N(3))] are also presented for comparison.     

Formation of a uranium trithiocarbonate complex via the nucleophilic addition of a sulfide-bridged uranium complex to CS2

The uranium(IV)/uranium(IV) μ-sulfide complex [{(((Ad)ArO)(3)N)U}(2)(μ-S)] reacts with CS(2) to form the trithiocarbonate-bridged complex [{(((Ad)ArO)(3)N)U}(2)(μ-κ(2):κ(2)-CS(3))]. The trithiocarbonate complex can alternatively be formed in low yields from low-valent [(((Ad)ArO)(3)N)U(DME)] through the reductive cleavage of CS(2).