Chelation of Na+ cations in nonaqueous solvents. Structural requirements and methodological considerations

Intrinsic formation constants for complexes of Na⁺ ions with a series of polyamines have been determined from²³Na NMR measurements in binary mixtures of tetrahydrofuran (THF) and amines. The results show in a totally unambiguous manner a regular decrease in the magnitude of the chelate effect with the number of atoms intervening between the nitrogen ligators. The key assumption, tetracoordination of the cation, is critically examined, and experimental evidence is adduced in its support.     

On a site-selective exafs experiment using optical emission

X-ray-excited optical luminescence (XEOL) is known to offer an alternative detection scheme of EXAFS spectra. Although this secondary emission appears restricted to a rather limited number of systems, we show that it can afford, under appropriate circumstances, an interesting property of site selectivity. The case of a ZnO + ZnTPP mixture was chosen as an illustrative example. The relevant formulation of the phenomenon for powdered samples is developed and the requirements for site selectivity are discussed.     

Chemistry of the phenoxathiins and isosterically related heterocycles. XXV . Synthesis of 1,6-diazathianthrene from 3-mercaptopyridin-2(1H)-thione via a novel dehydrothiolation reaction in the presence of triethylamine

The generation of the dianion of 3-mercaptopyridin-2(1H)-thione with triethylamine in N,N-dimethylform-amide followed by reaction in the presence of 2-chloronitrobenzene fails to give 1-azathianthrene which is formed in good yield when sodium hydride was employed as the base. The principle product isolated from the reaction was instead 1,6-diazathianthrene. Mechanistic considerations are discussed.     

Makroskonische Diffusion von Methanol in einen Natrium-und einen dekationisierten Y-Zeolith

Ohne Zusammenfassung