Die Zerlegungsgesetze für die Primideale eines beliebigen algebraischen Zahlkörpers im Körper derl-ten Einheitswurzeln

Ohne Zusammenfassung     

Group 6 metal carbonyl complexes of a bulky phosphine: The crystal structures of tris(trimethylsilyl)phosphine-M(0)pentacarbonyl, M = chromium, molybdenum, and tungsten

The crystal structures of M(P{Si(CH₃)₃}₃)(CO)₅, M = Cr (1), Mo (2), and W (3), have been determined. Crystal data for 1, trigonal crystal system, space group = P3₁, a, b = 9.2118(6) ?, c = 22.416(3) ?, V = 1647.3(2) ?³, Z = 3; for 2, trigonal crystal system, space group = P3₂, a, b = 9.3394(3) ?, c = 22.7375(12) ?, V = 1717.56(12) ?³, Z = 3; trigonal crystal system, space group = P3₂, a, b = 9.3147(5) ?, c = 22.6955(16) ?, V = 1705.33(18) ?³, Z = 3. All three structures show distorted octahedral coordination environments around the metal center and exhibit especially long M–P bond distances, illustrating the unique steric and electronic properties of this bulky phosphine ligand. The ³¹P{¹H} NMR spectra of the compounds are also reported.     

Insulator-to-metal transition in selenium-hyperdoped silicon: observation and origin

Hyperdoping has emerged as a promising method for designing semiconductors with unique optical and electronic properties, although such properties currently lack a clear microscopic explanation. Combining computational and experimental evidence, we probe the origin of sub-band-gap optical absorption and metallicity in Se-hyperdoped Si. We show that sub-band-gap absorption arises from direct defect-to-conduction-band transitions rather than free carrier absorption. Density functional theory predicts the Se-induced insulator-to-metal transition arises from merging of defect and conduction bands, at a concentration in excellent agreement with experiment. Quantum Monte Carlo calculations confirm the critical concentration, demonstrate that correlation is important to describing the transition accurately, and suggest that it is a classic impurity-driven Mott transition.     

Preparation,Structure, and Properties of All Possible Cyclic Dimers (Diolides) of 3-Hydroxybutanoic Acid

In connection with the proposed structure of a trans-membrane cellular ion channel consisting of a complex between poly[(R)-3-hydroxy butanoate] (P(3-HB)) and calcium polyphosphate, CaPP_i (ca. 150 units each), which is supposed to contain s-cis-bonds or even more highly strained ester conformations, we have prepared and studied the properties of the cyclic dimer of 3-HB, the diolide 1 . All possible forms of 1 , the rac-, the meso-, and the enantiomerically pure (R,R)- and (S,S)-compounds were prepared, purified, and characterized. The synthesis (Scheme 1) started from dimethyl succinate with the key step being the Baeyer-Villiger oxidation of the rac- and meso-2,5-dimethylcyclohexane-1,4-diones 5 . The rac-diolide 1 was resolved by preparative chromatography on a Chiralcel OD column (Fig.1). The crystal structures of rac- 1 (Fig.3) and of meso- 1 (Fig.5) were determined by X-ray diffraction: the diolides 1 contain s-cis-ester bonds and an ester group with a conformation half way to the transition state of rotation (Fig.2). Strain energies for the diolides 1 of up to 17.8 kcal/mol are suggested. Accordingly, these compounds show reactivities similar to those of carboxylic-acid anhydrides or even acid chlorides. They cannot be chromatographed on silica gel, and they react with primary, secondary, and tertiary alcohols, and with amines to form derivatives of open chain 3-HB ‘dimers’, hydroxy acids 6 , esters 7 , and amides 8 (Scheme 2). The rate of acid-catalyzed ring opening of the diolides 1 with alcohols has been measured (Fig.6 and 7). From the results described, we conclude that it is unlikely for strained and reactive ester conformations to occur as part of ion channels through phospholipid bilayers of cells.