Sr2Si5N8 und Ba2Si5N8 werden phasenrein durch Umsetzung von Siliciumdiimid mit den jeweiligen Metallen Strontium bzw. Barium unter Stickstoffatmosphäre in einem speziellen Hochfrequenzofen bei 1 550 bis 1 650°C synthetisiert. Sr2Si5N8 (Pmn21, a = 571,0(2), b = 682,2(2), c = 934,1(2) pm, Z = 2, R = 0,037, wR = 0,021) und Ba2Si5N8 (Pmn21, a = 578,3(2), b = 695,9(2), c = 939,1(2) pm, Z = 2, R = 0,022, wR = 0,018) kristallisieren isotyp und sind aus M2+‐Ionen (M = Sr bzw. Ba) sowie einer kovalenten dreidimensionalen Raumnetzstruktur eckenverknüpfter SiN4‐Tetraeder aufgebaut. Je 4 N sind an zwei bzw. drei Si gebunden. Die an je zwei Si gebundenen N leisten den dominierenden koordinativen Beitrag für die M2+‐Ionen.

Using differential scanning calorimetry (DSC) measurements in combination with structural and optical characterization we have investigated the formation conditions of different phases of tris(8‐hydroxyquinoline)aluminum (Alq3). We have identified the δ‐phase as a high‐temperature phase of Alq3 being composed of the facial stereoisomer, and report an efficient method to obtain blue luminescent Alq3 by a simple annealing process. This allows the preparation of large amounts of pure δ‐Alq3 by choosing appropriate annealing conditions, which is necessary for further characterization of this blue‐luminescent phase, and offers the possibility of fabricating blue organic light‐emitting devices (OLEDs) from this material.

We report on two different crystalline phases of tris͑8-hydroxyquinoline͒ aluminum (Alq 3) which were obtained by thermal sublimation in a horizontal glass tube. These phases are investigated by x-ray powder diffraction, Raman and infrared spectroscopy, and low temperature photoluminescence measurements. Apart from the already known ␣ phase we could identify a new crystalline phase of Alq 3 (␦-Alq 3) showing blueshifted fluorescence. As compared to the ␣ phase this new phase is characterized by a larger unit cell volume, a reduced number of Raman lines in the energy range between 70 and 700 cm Ϫ1 , a blueshift of the photoluminescence maximum by about 0.2 eV, and a decreased intersystem crossing to the triplet state. These differences are interpreted in terms of the isomery of the Alq 3 molecule. It is supposed that the new phase contains the facial isomer, whereas in the other phases only the meridianal isomer was reported. Low temperature photoluminescence spectra show a well-resolved vibronic progression with about the same spacing of 550 cm Ϫ1 for both crystalline phases of Alq 3. Site-selective photoluminescence measurements reveal the existence of an additional redshifted featureless emission, which is ascribed to energy relaxation into low-lying states.

Crystal structures of both one-and two-layer hydrates of sodium fluorohectorite were refined against single crystal data for the first time because melt synthesis yielded a sodium fluorohectorite showing little stacking disorder as compared to natural clays. In both hydrate phases, the relative shift of adjacent 2:1 layers is fixed by hydrogen-bonding between water molecules coordinated to interlayer cations and basal oxygen atoms of tetrahedral sheets encompassing the interlayer space. Despite some apparent diffuse scattering, a decent single crystal refinement of the semi-ordered structure of the onelayer hydrate is achieved, revealing structural details of the interlayer spacing for the first time. For the two-layer hydrate the structural model proposed for vermiculites is confirmed but a different ordering pattern of interlayer [Na(H 2 O) 6 ] + is suggested. While in the two-layer hydrate sodium cations reside at the centre of the interlayer space, in the one-layer hydrate sodium is displaced from the centre of the interlayer space either towards the upper or towards the lower tetrahedral sheet. This displacement allows for coordination to the hexagonal cavity on one side while the coordination sphere of sodium is completed by three coordinating water molecules on the other side. These three water molecules in turn are involved in hydrogen bonding to the opposite tetrahedral sheet.

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The various reactive sites in the 16 e complex 1 invite addition reactions with alkynes. After addition of 2 to one of the Rh-S bonds, B-H activation takes place which finally leads to the complex 3, in which a B(3)/B(6)-disubstituted o-carborane cage is present for the first time.

A route to fully miscible polyethylene (PE) nanocomposites has been established based on polymer-brush-coated nanoparticles. These nanoparticles can be mixed with PE at any ratio, with homogeneous dispersion, and without aggregation. This allowed a first systematic study of the thermomechanical properties of PE nanocomposites without interference from aggregation effects. We observe that the storage modulus in the semicrystalline state and the softening temperature increase significantly with increasing nanoparticle content, whereas the melt viscosity is unaltered by the presence of nanoparticles. We show that the complete miscibility with the semicrystalline polymer matrix and the improvement of thermomechanical properties in the solid state is caused by the PE-coated nanoparticles being nucleating agents for the crystallization of PE. This provides a general route to fully miscibility nanocomposites with semicrystalline polymers.

The resistance of metal-organic frameworks towards water is a very critical issue concerning their practical use. Recently, it was shown for microporous MOFs that the water stability could be increased by introducing hydrophobic pendant groups. Here, we demonstrate a remarkable stabilisation of the mesoporous MOF Al-MIL-101-NH2 by postsynthetic modification with phenyl isocyanate. In this process 86 % of the amino groups were converted into phenylurea units. As a consequence, the long-term stability of Al-MIL-101-URPh in liquid water could be extended beyond a week. In water saturated atmospheres Al-MIL-101-URPh decomposed at least 12-times slower than the unfunctionalised analogue. To study the underlying processes both materials were characterised by Ar, N2 and H2 O sorption measurements, powder X-ray diffraction, thermogravimetric and chemical analysis as well as solid-state NMR and IR spectroscopy. Postsynthetic modification decreased the BET equivalent surface area from 3363 to 1555 m(2)  g(-1) for Al-MIL-101-URPh and reduced the mean diameters of the mesopores by 0.6 nm without degrading the structure significantly and reducing thermal stability. In spite of similar water uptake capacities, the relative humidity-dependent uptake of Al-MIL-101-URPh is slowed and occurs at higher relative humidity values. In combination with (1) H-(27) Al D-HMQC NMR spectroscopy experiments this favours a shielding mechanism of the Al clusters by the pendant phenyl groups and rules out pore blocking.