Band 224, Heft 11

A highly diastereoselective synthesis (>98%) of novel chiral (3a S )-4-oxo-6-phenyl-2,3,3a,4,6,14-hexahydro-1H-naphtho[1,2-e]pyrrolo[1′,2′:3,4][1,3,2]oxazaborolo-[2,3-b][1,3,2]oxazaborinin-15-ium-6-uide ( 2a ) and (3a S )-6-(naphthalen-2-yl)-4-oxo-2,3,3a,4,6,14-hexahydro-1H-naphtho[1,2-e]pyrrolo[1′,2′:3,4][1,3,2]oxazaborolo[2,3-b][1,3,2] oxazaborinin-15-ium-6-uide ( 2b ) compounds is described and details of the crystal structures are presented.

The paper reports structural and microchemical investigations of low-dimensional semiconducting materials by combined imaging and spectroscopical techniques of transmission electron microscopy (TEM). The materials systems under investigation comprise graded (Al,Ga)As layers, (In,Ga)As quantum wires in V-grooved (001)InP, and (In,Ga)As quantum dots in GaAs. In order to elucidate structural peculiarities of these objects conventional and high-resolution TEM (CTEM/HRTEM) were performed, whereas information about the chemical composition and element distribution was obtained through electron energy loss spectroscopy (EELS), energy-filtered TEM (EFTEM), and energy-dispersive X-ray spectroscopy (EDXS). Particularly, the application possibilities of EFTEM are here demonstrated for revealing the local element content at high lateral resolution in a semi-quantitative manner.

Cyclic multiple twins as nanoobjects that display nearly regular polyhedron shape variety together with strongly anisotropic shape variations due to growth processes are reviewed with regard to their unique shape evolution based on the specific formation modes as well as on the particular structure of twin-related subunits. The review includes (i) the shape variations due to growth by stacking of tetrahedral subunits, (ii) the role of growth conditions in the shape evolution of multiply twinned nanoparticles, and (iii) the modes of twin-based anisotropic growth including branching growth and unidirectional growth. The particular structures are introduced making use of electron microscopy structural characterization of multiply twinned metal nanoparticles as well as some non-metal examples, and instructive models of the various configurations.

Powder neutron diffraction was used to investigate Zr 10 Sc 4 O 26 , the so called γ -phase in the zirconia scandia system. This fluorite related anion deficient compound with composition MX 1.86 crystallizes in space group R -3 and lattice constants a = 952.7(3) pm and c = 1745.3(4) pm. Anion vacancies are inserted on the 6c sites in R -3. The neutron data as well as the periodic density-functional calculations performed count for a divacancy model. The paired defect is more stable by 29 kJ/mol than any model with unpaired vacancies including the model with the 1/2[111] F (index F = fluorite) vacancy separation along an empty anion cube.

The synthesis, spectroscopic characterization and crystal structures of two uranyl complexes, [UO 2 (SALEN)(DMF)] ( 1 ) and [UO 2 (BPHA) 2 (DMF)] ( 2) {SALEN = N,N′-ethylenebis(salicylimine), DMF = N,N-dimethylformamide, BPHA = N-phenyl benzohydroxamate} are described. The coordination geometry around the metal center in the mononuclear complexes can be best described as distorted pentagonal bipyramidal with an almost linear uranyl moiety. In addition to the van der Waal´s interactions, the crystal packing in the complexes is stabilized by weak intermolecular C–H…O hydrogen bonds involving the uranyl oxygen atoms, so generating two-dimensional arrays in both crystal structures.

The synthesis, characterization and crystal structure of the title compound, N -ferrocenoyl- L -Pro- L -Leu-Gly-OMe (Fc-PLG), were reported in this paper. The title compound crystallized in a monoclinic system, space group C2 with Z = 4, a = 20.803(3) Å, b = 6.4428(4) Å, c = 20.557(2) Å, α = 90°, β = 115.498(5)°, γ = 90°; R = 0.0451. The Cp rings in the ferrocenoyl group are nearly coplanar, making a dihedral angle of 178.2 (4)°, while the substituted cyclopentadienyl ring and the proline ring are virtually coplanar with a very small twist angle of 14.0°. Strong hydrogen bonds between the Gly amide group N13 and the Pro carbonyl group O11 (d (N … O) = 2.835 Å) make the molecules fold into a β -turn conformation.

Bisazomethine compounds with 2-hydroxynaphthalene moieties belong to the few organic pigments which show fluorescence in the solid state. The condensation products of hydrazine with 4-formyl-3-hydroxy-2-naphthoic acid-4′-methoxyanilide (C 38 H 30 N 4 O 6 ), as well as the corresponding 4′-chloro and 2′,5′-dichloro derivatives (C 36 H 24 Cl 2 N 4 O 4 and C 36 H 22 Cl 4 N 4 O 4 ) are almost insoluble in all common solvents, even at temperatures of 200 °C. The 4′-methoxy derivative exists in at least two polymorphs. Small crystals of the a-phase could be obtained from N -methylpyrrolidone at 150 °C. A crystal with a size of just 1 × 2 × 10 μm 3 was sufficient to determine the crystal structure by micro-focus synchrotron-X-ray diffraction. The phenyl groups are disordered. The crystal structure of the β -phase of the 4′-methoxy derivative, as well as the structures of the two other derivatives were determined from X-ray powder diffraction data. The crystal structures were solved by real-space methods using the program DASH , the Rietveld refinement was done with the program TOPAS . The 2′,5′-dichloro derivative crystallises in P -1, Z = 1, all other phases in P 2 1 / c with Z = 2. All compounds form intramolecular hydrogen bonds, which explain the solid state fluorescence.