Ma?analytische Bestimmung des Quecksilbers

Ohne Zusammenfassung     

A theoretical investigation of the complete valence ionization spectra of cyanamide,isocyanamide, diazirine and diazomethane

The ionization potentials of the four isomeric molecules cyanamide, isocyanamide, diazirine and diazomethane are computed in the entire valence region by the Green function method. The Koopmans' ordering of the one-electron level is confirmed. The computations permit to unambiguously assign the photoelectron spectra of cyanamide and diazirine, and to reassign part of the spectrum of diazomethane. For isocyanamide, for which a PES spectrum is not available, the results of the computations are believed to represent a good approximation to the true ionization potentials. The usual breakdown phenomenon of the molecular-orbital model of ionization in the inner valence shell is observed and discussed. A strong hole-mixing effect is found in the isocyanamide molecule.     

ESR of selenium pairs (Se+2) in silicon

A slight anisotropy of the Se⁺₂ ESR is resolved, revealing [111] axial symmetry. The pair groundstate is a_2u in D_3d symmetry, consistent with the almost complete s-character at the Se sites. The value of g₆ is correlated with the binding energy of Se⁺₂ in a way recently established for simple deep donors in Si.     

Syntheses and cation binding properties of 12-membered ring nitrogen-pivot lariat ethers

The efficient synthesis of several 12-membered ring, N-pivot lariat ethers are reported and it is shown that binding to sodium cations is generally weak except when an oligoethyleneoxy sidearm is long enough to provide additional solvation.     

Synthesis and characterization of cross-linked reverse micelles

The design and synthesis of a new cross-linkable amphiphile is reported. Solutions of the amphiphile in a toluene/water mixture form reverse micelles as indicated by dynamic light scattering and NMR spectroscopy. As indicated by dynamic light scattering, TEM, and NMR spectroscopy data, these reverse micelles can be cross-linked without drastically changing the radius of the reverse micelles. Mixed reverse micelles are also characterized and cross-linked. The cross-linked reverse micelles are demonstrated to facilitate phase transfer and can be used to site isolate a catalyst.     

Detection of homocysteine and cysteine

At elevated levels, homocysteine (Hcy, 1) is a risk factor for cardiovascular diseases, Alzheimer's disease, neural tube defects, and osteoporosis. Both 1 and cysteine (Cys, 3) are linked to neurotoxicity. The biochemical mechanisms by which 1 and 3 are involved in disease states are relatively unclear. Herein, we describe simple methods for detecting either Hcy or Cys in the visible spectral region with the highest selectivity reported to date without using biochemical techniques or preparative separations. Simple methods and readily available reagents allow for the detection of Cys and Hcy in the range of their physiologically relevant levels. New HPLC postcolumn detection methods for biological thiols are reported. The potential biomedical relevance of the chemical mechanisms involved in the detection of 1 is described.     

New polyamide cryptand for anion binding

An anion receptor derived from a tren-based amide cryptand with pyridine spacers has been synthesized and characterized. Two crystal structures are reported: the hydrochloride salt and the fluoride complex. The cryptand shows extremely high binding with fluoride ion in DMSO-d6. Both the crystal structure and solution 19F NMR data indicate an encapsulated fluoride ion with very high symmetry.     

One-pot multi-step synthesis: a challenge spawning innovation

Creating one-pot synthetic routes is a challenge that is already spawning new chemistry, enzymes, materials, and mechanistic insight. Through one-pot reactions, the chemical products that add value to our lives can be produced with less waste and greater economic benefits. Within this Emerging Area, we describe models for designing one-pot reactions as well as advanced catalysts created to facilitate their realization.