Nitrous Oxide as a Hydrogen Acceptor for the Dehydrogenative Coupling of Alcohols

The oxidation of alcohols with N₂O as the hydrogen acceptor was achieved with low catalyst loadings of a rhodium complex that features a cooperative bis(olefin)amido ligand under mild conditions. Two different methods enable the formation of either the corresponding carboxylic acid or the ester. N₂ and water are the only by‐products. Mechanistic studies supported by DFT calculations suggest that the oxygen atom of N₂O is transferred to the metal center by insertion into the Rh?H bond of a rhodium amino hydride species, generating a rhodium hydroxy complex as a key intermediate.     

Micellar spheres in a high frequency oscillatory field

The viscoelasticity of aqueous micellar solutions of two oxyethylene/oxybutylene block copolymers (E(92)B(18) and B(20)E(510)) has been investigated using a torsional resonator operated at 26 kHz. For both systems considered, values of the dynamic viscosity (eta'(infinity)) point to partial draining of the micellar corona induced by the high-frequency oscillatory field. At low effective volume fractions, values of the elastic modulus (G'(infinity)) indicate that the repulsive interactions between micelles can be modeled by a power law function u(r) proportional to 1/r(nu) with exponents close to 13 and 6 for copolymers E(92)B(18) and B(20)E(510) respectively. At a critical copolymer concentration (c*) plots of log(G'(infinity)) against log(c) deviate from the straight lines established at low concentrations, implying that the systems undergo ergodic/nonergodic transitions.     

Patterned polyfluorene surfaces by functionalization of nanoimprinted polymeric features

A new procedure is described for surface grafting polymer brushes by step-growth polymerization from initiator-embedded polymeric thin films and micron- and nanometer-scale patterns. An imprint lithographic process, nanocontact molding, was used to prepare thin patterned cross-linked polyacrylate network films on silicon wafers that incorporated 4-bromostyrene in the networks. These networks present reactive 4-bromophenyl functionality at the surface that act as attachment sites for the subsequent Ni(0)- mediated step-growth condensation polymerization of 2,7-dibromo-9,9-dihexylfluorene The step-growth polymerization medium consisted of 2,7-dibromo-9,9-dihexylfluorene, Ni(0)-catalyst, and bipyridine in a toluene/dimethylformamide solvent mixture. The resulting growth of polydihexylfluorene brushes from the patterned surface was monitored by contact angle, optical spectrometry, surface profilometry and AFM. Brush growth was conducted from patterned features ranging from 100 microm to 100 nm in width and 50 nm in height. The optical and fluorescence behavior of the polyfluorene brushes was similar to that of thin polyfluorene films made by spin coating.     

Isotopic pattern and accurate mass determination in urine drug screening by liquid chromatography/time-of-flight mass spectrometry

An efficient method was developed for toxicological drug screening in urine by liquid chromatography coupled with electrospray ionization time-of-flight mass spectrometry. The method relies on a large target database of exact monoisotopic masses representing the elemental formulae of reference drugs and their metabolites. Mass spectral identification is based on matching measured accurate mass and isotopic pattern (SigmaFit) of a sample component with those in the database. Data post-processing software was developed for automated reporting of findings in an easily interpretable form. The mean and median of SigmaFit for true-positive findings were 0.0066 and 0.0051, respectively. The mean and median of mass error absolute values for true-positive findings were 2.51 and 2.17 ppm, respectively, corresponding to 0.65 and 0.60 mTh. For routine screening practice, a SigmaFit tolerance of 0.03 and a mass tolerance of 10 ppm were chosen. Ion abundance differences from urine extracts did not affect the accuracy of the automatically acquired SigmaFit or mass values. The results show that isotopic pattern matching by SigmaFit is a powerful means of identification in addition to accurate mass measurement.     

Superhydrophobic surfaces having two-fold adjustable roughness prepared in a single step

A fast and reliable method is reported for fabricating superhydrophobic surfaces. The method combines microstructure replication with polymer phase inversion and can be applied to a wide variety of polymers. This method provides a surface that contains roughness on two independently controllable levels, i.e., the microstructure level and the level of porosity stemming from the phase inversion. Both levels were optimized separately, resulting in water contact angles up to 167 degrees.     

Indachlorins: Nonplanar Indanone‐Annulated Chlorin Analogues with Panchromatic Absorption Spectra between 300 and 900 nm

Indaphyrins, pyrrole‐modified porphyrins containing a cleaved pyrrole β,β′‐bond and two annulated indanone moieties, possess unusually broadened and redshifted UV/Vis spectra because of their π‐expanded chromophores. The parent free base indaphyrin has been crystallographically characterized, highlighting its strongly ruffled conformation incorporating a helimeric twist. It was shown to be susceptible to regiospecific derivatizations at the opposite side of the ring‐cleaved pyrrole (dihydroxylation, followed by functional group transformations of the resulting diol functionality), generating indaphyrin‐based chlorin analogues, indachlorins, that incorporate a dihydroxypyrroline, pyrrolindione, oxazolone, or a morpholine moiety. Structural modifications resulted in further broadening and hyper‐ and bathochromic shifts of the optical spectra, some of which possess a nearly panchromatic absorption between 300 to well above 900 nm. The extents to which these modifications affect their solid‐state conformations were analyzed.     

Elemental distribution and thermoelectric properties of layered tellurides 39R-M(0.067)Sb(0.667)Te(0.266) (M=Ge, Sn)

The isostructural phases 39R‐Ge_0.067Sb_0.667Te_0.266 (R$\bar 3The isostructural phases 39R-Ge(0.067)Sb(0.667)Te(0.266) (R3m, a=4.2649(1), c=75.061(2) ?) and 39R-Sn(0.067)Sb(0.667)Te(0.266) (R3m, a=4.2959(1), c=75.392(2) ?) were prepared by quenching stoichiometric melts of the pure elements and subsequent annealing at moderate temperatures. Their structures are comparable to "superlattices" synthesized by layer-by-layer deposition onto a substrate. These structures show no stacking disorder by electron microscopy. The structure of the metastable layered phases are similar to that of 39R-Sb(10)Te(3) (equivalent to Sb(0.769)Te(0.231)), which contains four A7 gray-arsenic-type layers of antimony alternating with Sb(2)Te(3) slabs. Joint refinements on single-crystal diffraction data using synchrotron radiation at several K edges were performed to enhance the scattering contrast. These refinements show that the elemental distributions at some atom positions are disordered whereas otherwise the structures are long-range ordered. The variation of the elemental concentration correlates with the variation in interatomic distance. Z-contrast scanning transmission electron microscopy (HAADF-STEM) on 39R-Ge(0.067)Sb(0.667)Te(0.266) confirms the presence of concentration gradients. The carrier-type of the isostructural metal (A7-type lamellae)-semiconductor heterostructures (Ge/Sn-doped Sb(2)Te(3) slabs) varies from n-type (Ge(0.067)Sb(0.667)Te(0.266)) to p-type (Sn(0.067)Sb(0.667)Te(0.266)). Although the absolute values of the Seebeck coefficient reached about 50-70 μV/K and the electrical conductivity is relatively high, the two isotypic phases exhibit a maximal thermoelectric figure of merit (ZT) of 0.06 at 400 °C as their thermal conductivity (κ≈8-9.5 W/mK at 400 °C) lies interestingly in between that of antimony and pure Sb(2)Te(3).     

Hydrosilylation of alkynes by Ni(CO)3-stabilized silicon(II) hydride

Not copy and paste: Although β-diketiminato ligands have been employed for the stabilization of Ge(II) and Sn(II) hydrides, the corresponding Si(II) hydride is not accessible. However, coordination of silicon(II) to a {Ni(CO)(3)} fragment allowed the isolation of the first Si(II) hydride metal complex 1. This complex was used for the first silicon(II)-based and Ni(0)-mediated, stereoselective hydrosilylation of alkynes. R = phenyl, tolyl.     

Efficient copper(II)-catalyzed transamidation of non-activated primary carboxamides and ureas with amines

Amid(e) them all: primary carboxamides and ureas react with aromatic and aliphatic amines in the presence of a copper catalyst to give a wide range of functionalized amides.