New possibility for an organic semiconductor: a smectic liquid crystalline semiconductor having a long conjugated core and two long alkyl chains

We report a new possibility for liquid crystalline organic semiconductors. These materials exhibit smectic liquid crystalline phases, in which the molecules assume a smectic molecular order by self-assembly. Because of the strong dispersion force among long alkyl chains, on cooling, smectic molecular order was retained at room temperature. A charge transport ability was also retained. The conductivity of a device having smectic liquid crystalline order is about 5×10⁷ that of a device with no smectic order. The current - voltage characteristic of the device has a very sharp increase at low threshold voltage (5 V). A high carrier mobility of 1.8×10^-2 was observed in the smectic phase of one of the compounds studied (e).     

X-ray diffraction analysis of the layer structure in a ferroelectric liquid crystal with a chiral nematic-chiral smectic C phase transition

A half-V-shaped switching ferroelectric liquid crystal (FLC) is a promising candidate for fast response displays. In the half-V FLC display, a liquid crystal with a chiral nematic-chiral smectic C phase transition is used, and the smectic layer is formed by cooling from N* to SmC* with an applied d.c. field. We studied the layer structure by means of X-ray measurements for two axes (ω and χ). By using a point-focused X-ray tube and optimizing the slit width, we succeeded in the two-axis measurement with a commercial X-ray system. The ω-χ profile of the half-V FLC showed two broad peaks in an arc-shaped high-intensity area. Our interpretation of this result is that the major part of the layer consists of a tilted-bookshelf structure and that the minor part consists of a near-bookshelf structure. Since optical microscopy observations on the half-V FLC cells showed a stripe-shaped texture, we consider that the coexistence of the tilted-bookshelf and the near-bookshelf structures forms the stripe-shaped patterns. The radius of the arc-shaped high-intensity area was nearly equal to the molecular tilt angle. This result can explain why the half-V FLC showed a desirable black appearance in spite of the stripe-shaped texture.     

Catalysis of giant palladium cluster complexes. Highly selective oxidations of primary allylic alcohols to α,β-unsaturated aldehydes in the presence of molecular oxygen

A giant Pd cluster, Pd₅₆₁phen₆₀(OAc)₁₈₀, has high catalytic activity for the selective oxidations of various primary allylic alcohols to the corresponding α,β-unsaturated aldehydes in the presence of molecular oxygen under mild reaction conditions. A Pd cluster anchored on TiO₂ also catalyzes the above oxidations; the heterogeneous Pd₅₆₁ cluster catalyst is easily separated from the reaction mixture and is reusable.     

A novel class of materials for ferroelectric liquid crystals containing siloxy chain end groups

Novel liquid crystals containing a siloxy chain as an end tail group instead of an alkyl chain were synthesized. The substitution effects were studied for ferroelectric liquid crystal materials. It was found that the temperature range for the chiral smectic C phase was reduced and shifted to lower temperature in comparison with the analogous alkyl chain derivatives. The crystallinity of the siloxy chain derivatives decreased and cholesteric phases were not observed. The influence of siloxy chains on ferroelectric liquid crystal properties, especially spontaneous polarizations and tilt angles, also greatly depended upon the mesogenic group structure. The X-ray diffraction results showed that the end tail group occupied a larger thickness in the chiral smectic C layer for the siloxy chain derivative than that for the alkyl chain derivative.     

In vivo fate of superparamagnetic iron oxides during sepsis

The enzymatic generation of nitric oxide (NO) in vivo has been reported to be modulated by ions, such as copper and iron. Superparamagnetic iron oxide (SPIO) or ferumoxides is a liver-specific magnetic resonance contrast agent that is taken up by the Kupffer cells, where NO is generated by inducible nitric oxide synthase (iNOS). Thus, it is important to evaluate SPIO in vivo under conditions, such as infectious disease, where significant amounts of NO are generated by iNOS. In this study, we monitored the pharmacokinetics of SPIO in the liver of septic-shock mice and rats. A significant decrease in the ferric iron EPR signal was observed during NO generation in septic-shock mice compared with control mice doped with only SPIO. These results were also confirmed in a model reaction system consisting of SPIO and the NO donor, S-nitroso-N-acetyl DL penicillamine (SNAP). We compared NO generation quantitatively in the liver of the septic-shock rats, either in the presence or absence of SPIO, and found that the presence of SPIO did not affect the NO-generating activity of NOS expressed in the liver. T2-weighted MR images of an agarose gel phantom containing different SPIO to NO donor (SNAP) ratios clearly demonstrated that the contrast enhancement by SPIO decreased with increasing NO at constant SPIO levels. The reduced contrast is most probably due to the reduction of ferric to ferrous irons, resulting in a decrease in paramagnetic relaxation of water protons. These results show that SPIO can be a versatile NO-sensitive indicator, especially employing MRI as a powerful tool to 'visualize' sites of NO generation.     

Grazing‐incidence small‐angle X‐ray scattering from Ge nanodots self‐organized on Si(001) examined with soft X‐rays

Grazing‐incidence small‐angle X‐ray scattering (GISAXS) measurements with soft X‐rays have been applied to Ge nanodots capped with a Si layer. Spatially anisotropic distribution of nanodots resulted in strongly asymmetric GISAXS patterns in the q_y direction in the soft X‐ray region, which have not been observed with conventional hard X‐rays. However, such apparent differences were explained by performing a GISAXS intensity calculation on the Ewald sphere, i.e. taking the curvature of Ewald sphere into account.     

Olefin hydrogenation catalysis of platinum nanocrystals with different shapes

We have investigated the catalysis of Pt nanocrystals for olefin hydrogenation in liquid phase by using several kinds of Pt nanocrystals with different shapes, whose results suggest that Pt cube shows the highest catalytic activity without significant shape change after the repeated hydrogenation. We prepared four nanocrystals according to our original methods: four kinds of Pt cubes (6.7, 8.2, 9.5, and 10.1 nm), Pt tetrahedron (4.6 nm), Pt nanowire (2.0 nm), and Pt cuboctahedron (7.5 nm) with high shape selectivity and narrow size distributions. To avoid the effect of different surface protecting agent on hydrogenation, we use the same polymer (polyacrylic acid) to stabilize four kinds of Pt nanocrystals. We adopted olefins with different structural characteristics, such as hexene, cyclohexene, cis-, and trans-stilbene. Turnover frequency (TOF) values for the hydrogenation of both cis- and trans-stilbene exhibit the following order: Pt cube > Pt cuboctahedron > Pt tetrahedron ≈ Pt nanowire, in accord with the ratio of Pt(100) on the surface of Pt nanocrystals. Raman spectroscopy of chemically adsorbed trans-stilbene on Pt cube and Pt tetrahedron indicates that the C–C double bonds of olefin group and phenyl group prefer to interact with Pt(100) facet, coinciding with its highest activity for olefin hydrogenation. The hydrogenation of cyclohexene as well as 1-hexene over Pt cubes with different sizes gave similar TOF values, suggesting that the hydrogenation takes place preferentially on the planes of Pt(100) facet in liquid phase.     

Environmentally friendly one-pot synthesis of alpha-alkylated nitriles using hydrotalcite-supported metal species as multifunctional solid catalysts

A ruthenium-grafted hydrotalcite (Ru/HT) and hydrotalcite-supported palladium nanoparticles (Pd(nano)/HT) are easily prepared by treating basic layered double hydroxide, hydrotalcite (HT, Mg(6)Al(2)(OH)(16)CO(3)) with aqueous RuCl(3)n H(2)O and K(2)[PdCl(4)] solutions, respectively, using surface impregnation methods. Analysis by means of X-ray diffraction, and energy-dispersive X-ray, electron paramagnetic resonance, and X-ray absorption fine structure spectroscopies proves that a monomeric Ru(IV) species is grafted onto the surface of the HT. Meanwhile, after reduction of a surface-isolated Pd(II) species, highly dispersed Pd nanoclusters with a mean diameter of about 70 A is observed on the Pd(nano)/HT surface by transmission electron microscopy analysis. These hydrotalcite-supported metal catalysts can effectively promote alpha-alkylation reactions of various nitriles with primary alcohols or carbonyl compounds through tandem reactions consisting of metal-catalyzed oxidation and reduction, and an aldol reaction promoted by the base sites of the HT. In these catalytic alpha-alkylations, homogeneous bases are unnecessary and the only by-product is water. Additionally, these catalyst systems are applicable to one-pot syntheses of glutaronitrile derivatives.     

Novel catalysis of dendrimer-bound Pd(0) complexes: sterically steered allylic amination and the first application for a thermomorphic system

Phosphinated dendrimer-bound Pd(0) complex catalysts show high stereoselectivity for allylic amination due to the surface congestion of dendrimers and can be easily recycled without loss of activity under thermomorphic conditions.