Cu<Superscript>I</Superscript> complexes with 2,2′-biquinolyl-containing polymeric ligands as electrocatalysts for the oxidative coupling of alkynes in the presence of dioxygen

Electrocatalytic oxidative coupling of terminal alkynes in the presence of atmospheric oxygen catalyzed by Cu^I complexes with polymeric biquinolyl ligands leads to the corresponding diynes in high yield. The reaction proceeds under mild conditions at a potential of Cu^II/Cu^I electroreduction (−0.55 V vs. Ag/AgCl/KCl) and is accompanied by O₂ reduction to H₂O.     

Inverse opal based on a polymer filler and transformation of its optical characteristics

Opal-like photonic crystals based on opal and inverse opal, which exhibit shifts of selective reflection bands toward both the long-wavelength and short-wavelength ranges with respect to the diffraction band of the initial opal consisting of SiO₂ spheres, have been grown. The contributions from the skeletons forming three-dimensional periodic structures and from the fillers to the spectral position of diffraction bands have been determined.     

Free radicals: XXVIII. Reaction of 2,4,6-triphenylpyranyl with (diacetoxy-λ3-iodanyl)benzene

The major product of the reaction of 2,4,6-triphenylpyranyl with (diacetoxy-λ³-iodanyl)benzene in acetonitrile and acetone was 2,4,6-triphenylpyrylium acetate. Analogous reaction in isopropyl alcohol resulted in the formation of methane, carbon dioxide, 1,3,5-triphenylpent-2-ene-1,5-dione, 2-benzoyl-3,5-diphenylfuran, 1,3,5-triphenylpenta-2,4-dien-1-one, and a small amount of 2,4,6-triphenylpyrilium acetate.     

Sequence of Phase Transitions in Solid Mbba

Combined neutron diffraction and Raman scattering measurements were carried out on a series of different phases of the same MBBA sample. The change in the diffraction patterns and in the optical spectra are used to indicate the transitions between the different phases investigated in the whole temperature range of interest. Besides the isotropic and nematic liquid crystalline phases, 7 different solid structures were found and a schematic phase diagram was constructed to show the thermal procedur for producing these phases.     

Gap Reduction of C60 and C70 at High Pressure

Abstract

The absorption spectra of the C₆₀ and C₇₀ are measured at pressures up to 19 GPa. The pressure dependence of the fundamental absorption edge position E(P) is determined for both materials. The initial value of dE/dP=?0.15 eV/GPa for the stronger-absorption region of C₆₀ decreases up to ?0.019 eV/GPa at 12 GPa. The weaker-absorption region located near the fundamental absorption edge shifts slower dE/dP=?0.05 eV/GPa. For the C₇₀ the initial value of dE/dP=?0.1 eV/GPa decreases up to ?0.029 eV/GPa at 10 GPa. All pressure induced changes are reversible in this pressure range.     

Electrochemical Properties of N-Methyl- and N-Phenyl-2,4,6-Triphenylpyridium Perchlorate

Russian Journal of Electrochemistry - The electrochemical properties of N-methyl- and N-phenyl-2,4,6-triphenylpyridinium perchlorates were studied by cyclic voltammetry (CV). The substituent at the...     

Collective behavior of light-induced droplets in smectic membranes

Collective behavior and organization of droplets in thin smectic membranes were investigated using polarized light microscopy. Droplets were nucleated in membranes by light illumination. We observed the formation of periodic hexagonal and square lattice structures from droplets at large droplet concentration. Nearly linear dependence between period of structure and droplet size was found. We observed that droplets are nucleated on dislocations and periodic chain of droplets may be formed along a dislocation.Received: 29 september 2003, Published online: 5 February 2004PACS: 61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures - 64.70.Md Transitions in liquid crystals - 68.03.Cd Surface tension and related phenomena     

Stability of a free-standing liquid-crystal film: The measurement of the interaction between the film surfaces

The interaction energy of the surfaces of a free-standing liquid-crystal film has been determined. The measurements are performed in a smectic phase below the melting temperature of a bulk sample T _C, in the temperature range of structural instability of thin films at T > T _C, and in a quasi-smectic phase at T > T _C. Two modes of smectic-layer motion in the film are detected: they lead to film thinning at T > T _C and film thickening at a low temperature. The measurement results are discussed in terms of recent theoretical concepts.