Synthesis and Molecular Structure of a Tripodal Triaminostibine

Reaction of the tripodal trilithium triamide [MeSi{SiMe₂N(Li)(p‐Tol)}₃(thf)₂] ( 1 ) with SbCl₃ in toluene gave the corresponding triaminostibine [MeSi{SiMe₂N(p‐Tol)}₃Sb] ( 2 ) in good yield. Its [2,2,2]bicyclooctane‐related cage structure, comprising the trisilylsilane unit and the triamidostibine fragment, was established by a single crystal X‐ray structure analysis: Space group P1, Z = 2, lattice dimensions at 293 K: a = 8.645(4), b = 10.029(5), c = 19.678(9) Å, α = 98.50(3)°, β = 97.46(3)°, γ = 94.80(3)°, R = 0.0216.     

Determination of biogenic quaternary ammonium compounds on fused silica capillary columns with a splitless injector as a chemical reactor/pyrolysis chamber

A conventional splitless injector is used as a pyrolysis chamber or chemical reactor for the N-demethylation of acetylcholine and other choline esters. The novel uses of 2-aminoethanol as a N-demethylation reagent in splitless injection and bonded-phase fused silica capillary columns in the separation of the tertiary amine derivatives of choline esters are described. A comparison is made between non-polar and moderately polar fused silica capillary columns in the separation of choline esters.     

Protein synthesis in cell-free reticulocyte lysates on multi-hour incubation

Cell-free protein synthesis in rabbit reticulocyte lysate translation mixtures has been studied during multi-hour incubations. In an impaired lysate obtained from cells stored at 0°C before lysis, and showing a low initial rate of synthesis, translation could be stimulated by a factor of 4 by including RNase inhibitor and additional ATP and GTP. In translation mixtures prepared from normal lysates, protein synthesis could be improved by ∼50% by the addition of excess GTP. The observed increases in protein synthesis were obtained by improved maintenance of the initial rate of synthesis.     

Infrared photochemistry of bis(trifluoromethyl) peroxide

Bis(trifluoromethyl) peroxide is readily dissociated by multiple infrared photon excitation at CO₂ laser wavelengths. The primary dissociation product is CF₃O; approximately 85% of the nascent radicals are further dissociated in the laser field to form CF₂O and F. The F atoms then react with the remaining CF₃O to produce CF₃OF. The formation of CF₃OF is strongly inhibited by addition of HI, which reacts preferentially with the F atoms.     

Multi-exciton spectroscopy on a self-assembled InGaAs/GaAs quantum dot

We report about spatially resolved magneto-optical experiments on a self-assembled InGaAs quantum dot. Using electron beam lithograpy for patterning a metal shadow mask we can isolate a single dot. This allows us to study the optical response of a single dot as a function of excitation power and magnetic field. We investigate the influence of many body interaction in the emission spectra for different exciton occupation numbers of the dot. The diamagnetic/orbital shift as well as Zeeman splitting in a magnetic field can be fully resolved and are used to identify the observed emission lines. Further we report on absorption properties of the quantum dot as a function of magnetic field. We analyse in detail the phonon-assisted absorption process connected with the GaAs LO-phonon 36 meV above the single-exciton ground state.     

Remarkable tolerance of ethynyl steroids to air and water in microwave-assisted hydrophosphinylation: Reaction scope and limitations

The microwave-assisted hydrophosphinylation of propargyl alcohols has been investigated using group 9 catalysts under solvent-free conditions as well as with pure water, ethyl lactate, or THF as the solvent. Reactions involving simple propargyl alcohols gave mixtures containing significant amounts of elimination products. In contrast, analogous reactions involving ethynyl steroids afforded a single species with only trace amounts of elimination products. The molecular structures of several derivatives have been determined and are discussed.     

Metal-metal bonds between group 12 metals and tin: structural characterization of the complete series of Sn-M-Sn (M=Zn,Cd, Hg) heterodimetallic complexes

Reaction of the lithium triamidostannate [MeSi[SiMe(2)N(p-Tol)](3)SnLi(OEt(2))] (1) with 0.5 molar equivalents of MCl(2) (M=Zn, Cd, Hg) in toluene afforded the corresponding heterodimetallic complexes [MeSi[SiMe(2)N(p-Tol)](3)Sn](2)M [M=Hg (2), Cd (3), and Zn (4)]. The molecular structures of the mercury and cadmium complexes were determined by X-ray diffraction and found to adopt a linear Sn-M-Sn metal-metal bonded array (d(Sn-Hg) 2.6495(2), d(Sn-Cd) 2.6758(1) A), these being the first Hg-Sn and Cd-Sn bonds to be characterized by X-ray diffraction. That the Hg-Sn bonds are shorter than the Cd-Sn bonds in the isomorphous complexes is attributed to relativistic effects in the mercury system. In contrast, the structure of the Zn analogue is unsymmetrical with one stannate unit being Sn-Zn bonded (d(Sn(1)-Zn) 2.5782(4) A), while the Zn(II) atom bridges two amido functions of the second stannate cage, thus representing a second isomeric form of these complexes. The different degree of metal-metal bond polarity is reflected in the (119)Sn NMR chemical shifts of the three complexes. Variable-temperature NMR studies and a series of (1)H ROESY experiments of the cadmium complex 3 in solution revealed a dynamic exchange between the two isomers.