Electrocatalytic oxidative cleavage of electron-deficient substituted stilbenes in acetonitrile-water employing a new high oxidation potential electrocatalyst. An electrochemical equivalent of ozonolysis

A series of symmetrical and unsymmetrical stilbenes bearing two or more strong electron-withdrawing groups were oxidatively cleaved to the corresponding aldehydes in high yield by electrocatalytic anodic oxidation in aqueous acetonitrile employing a new high oxidation potential triphenylamine electrocatalyst. The oxidations apparently involve the corresponding 1,2-diols, which are also converted to aldehydes in high yield under the same conditions.     

Solid-state NMR and computational chemistry study of mononucleotides adsorbed to alumina

Solid-state NMR spectroscopy and ab initio computational chemistry are used to determine the structure of the complex formed upon adsorption of the mononucleotide 2'-deoxyadenosine 5'-monophosphate (dAMP) to the surface of a mesoporous alumina. In this multi-technique approach, rotational-echo double-resonance NMR results reveal that the phosphate group of dAMP interacts predominantly with octahedrally coordinated aluminum species at the surface, and therefore, adsorption is modeled with both mono- and bidentate sorption of the nucleotide phosphate group with octahedral aluminum. 31P chemical shielding tensors are calculated from the structure of the lowest energy conformations, and these results are compared to tensor values extracted from analysis of spinning-sideband patterns in the experimental 31P cross-polarization magic-angle-spinning NMR spectrum. The chemical shift anisotropy and asymmetry parameter indicate that the binding is via a monodentate, inner-sphere complex.     

Na(1.5)Ag(1.5)MO3F3 (M = Mo, W): an ordered oxyfluoride derivative of the LiNbO3 structure

Na(1.5)Ag(1.5)MoO(3)F(3) and Na(1.5)Ag(1.5)WO(3)F(3) have been synthesized by solid state reactions and structurally characterized using synchrotron X-ray and neutron powder diffraction. Unlike the vast majority of salts containing [MO(3)F(3)](3-) anions (M = Mo, W) the oxyfluoride groups in Na(1.5)Ag(1.5)MoO(3)F(3) and Na(1.5)Ag(1.5)WO(3)F(3) are orientationally ordered, so that the Na(+) ions are coordinated by fluorine and the Ag(+) ions by oxygen. The resulting structure type, which has not previously been reported, is related to the LiNbO(3) structure, but the combination of Na/Ag ordering and orientational ordering of the [MO(3)F(3)](3-) anions produces a supercell that doubles the c-axis and changes the space group symmetry from R3 to R3. The use of hard (Na(+)) and soft (Ag(+)) cations to direct the orientational ordering of polar oxyfluoride building units provides a new approach to the design of polar materials.     

Acentric 2-D ensembles of D-br-A electron-transfer chromophores via vectorial orientation within amphiphilic n-helix bundle peptides for photovoltaic device applications

We show that simply designed amphiphilic 4-helix bundle peptides can be utilized to vectorially orient a linearly extended donor-bridge-acceptor (D-br-A) electron transfer (ET) chromophore within its core. The bundle's interior is shown to provide a unique solvation environment for the D-br-A assembly not accessible in conventional solvents and thereby control the magnitudes of both light-induced ET and thermal charge recombination rate constants. The amphiphilicity of the bundle's exterior was employed to vectorially orient the peptide-chromophore complex at a liquid-gas interface, and its ends were tailored for subsequent covalent attachment to an inorganic surface, via a "directed assembly" approach. Structural data, combined with evaluation of the excited state dynamics exhibited by these peptide-chromophore complexes, demonstrate that densely packed, acentrically ordered 2-D monolayer ensembles of such complexes at high in-plane chromophore densities approaching 1/200 ?(2) offer unique potential as active layers in binary heterojunction photovoltaic devices.     

Electrochemical behavior of layered annulenes

The cyclic voltammetric behavior of a series of dimeric [14] annulenes was examined and compared with the monomer. The data suggest a signigficant degree of interaction between the annulene rings when a three-carbon chain connects them, little or no interaction with an eight-carbon chain, and weak interaction with a four-carbon chain.     

Laser-deposited thin films for butane detection

Thin films of ZnO and BaTiO₃, prepared by pulsed laser deposition (PLD), were studied as sensors for butane detection. The layers of ZnO, prepared on special substrates, were used as conductive-type sensors. The layers of ZnO and BaTiO₃, deposited on fused silica substrates, were tested by the optical m-line technique. Butane concentrations as low as 100 ppm were detected at room temperature.     

Stereochemical studies of fluoride ion-assisted reductions of ketones by organosilicon hydrides

The stereochemistry at the silicon and carbon centers has been studied in the fluoride ion-catalyzed reaction between ($\text{R}$)?(+)-α-naphthylphenylmethylsilane and several prochiral aromatic ketones which gives alkoxysilane product.     

Observation of epithermal 2S muonium

A slow muon beam was passed through a thin aluminium foil and the emerging beam was studied for the presence of muonium in the 2S state. The fraction and the velocity distribution of the 2S muonium was determined.