K5(UO2)2[Si4O12(OH)]: a uranyl silicate containing chains of four silicate tetrahedra linked by SiO...HOSi hydrogen bonds

A new uranium(VI) silicate, K5(UO2)2[Si4O12(OH)], has been synthesized by a high-temperature, high-pressure hydrothermal method. It crystallizes in the orthorhombic space group Pbcm (No. 57) with a = 13.1274(7) A, b = 12.2635(7) A, c = 22.233(1) A, and Z= 8. Its structure consists of unbranched chains of four silicate tetrahedra extending along the b axis linked together via corner-sharing by UO6 tetragonal bipyramids to form a 3-D framework, which delimits intersecting channels along the c and b axes to accommodate K+ cations. A hydrogen atom is bonded to a terminal oxygen of a terminal silicate in the oligosilicate anion. Adjacent chains are linked along the b axis by hydrogen bonds. The sample shows a resonance at 14.7 ppm the 1H MAS NMR spectrum, which is assigned to the SiO...HOSi hydrogen bond. A comparison of uranyl silicate structures is made.     

Trace Analysis of Heavy Metals with Two New Disodium Bisdithiocarbamates

Two chelating reagents, disodium N,N′-dibenzylethylenebisdithiocarbamate 1 and disodium piperazinebisdithiocarbamate 2, were synthesized and used to preconcentrate trace metals in aqueous samples. For analysis of Cu(II) using a UV-vis spectrometer, Beer's law was obeyed from 5.0 μg L^?1 to 6.0 mg L^?1 for reagent 1, and from 0.2 mg L^?1 to 6.0mg L^?1 for reagent. 2. The chelation ratio for reagent 1 to Cu(II) was determined to be 1:1, with a formation constant 1.0 × 10⁹ M^?l. The dependence of extraction and extraction efficiency of reagent 1 on pH was also studied with an atomic absorption spectrometer for nine heavy-metal ions-Cu(II), Fe(III), Pb(II), Co(II), Cr(VI), Ni(II), Zn(II), Mn(II) and Cd(II). Except Cr(VI) and Mn(II), the recovery yields of the other seven metal ions were almost quantitative at pH = 4 ? 6. The recovery was 82% for Cr(VI) at pH = 4 ? 5, and 52% for Mn(II) at pH = 6 ? 7.     

Upper rim allyl- and arylazo-coupled calix[4]arenes as highly sensitive chromogenic sensors for Hg2+ ion

The syntheses and chromogenic properties of calix[4]arenes, carrying 5,17-bisallyl-11,23-bis(p-X-phenyl)azo 3a-c, 5,11,17-triallyl-23-(p-X-phenyl)azo 4a-c, and 5,17-bis(hydroxypropyl)-11,23-bis(p-X-phenyl)azo groups on the upper rims 5a,b, are described. Unexpectedly, UV/vis spectra of the very popular 4-(4-nitrophenyl)azophenol-coupled calix[4]arenes 3c and 4c did not show any shift in lambda(max) when 10 different metal perchlorates were added separately to the host in a methanol-chloroform (v/v = 1/399) cosolvent. In contrast, the absorption spectra of calix[4]arenes with either 4-methoxyphenylazo (3b-5b) or 4-phenylazo (3a-5a) on the upper rim showed substantial bathochromic shifts (Deltalambda = 128-162 nm) upon the addition of soft metal ions (such as Hg(2+), Cr(3+), and Cu(2+)). The 4-(4-methoxyphenyl)azophenol-coupled calix[4]arenes (the 3b-5b series) are found to be highly sensitive for mercury ion (Hg(2+)) among the 10 different metal ions screened. Strong interactions between Hg(2+) ion and the 4-(4-methoxyphenyl)azophenol(s) as well as the p-allyl groups are corroborated by the (1)H NMR studies of 3a,b.Hg(2+) complexes. Furthermore, Job's plots revealed 1:1 binding stoichiometry for all these p-allyl- and arylazo-coupled calix[4]arenes with transition metal ions, and Benesi-Hilderbrand plots were used for the determination of their association constants.     

A Convenient Halogenation Procedure for the Preparation of α-Halocarbonyl Compounds

Except for substituted acetophenones (p-Y-C₆H₄COCH₃, Y=H, Br, CH₃O), simple ketones, β-ketoesters and 1,3-diketones reacted smoothly with a preformed homogeneous mixture of hydrochloric acid and potassium permanganate in acetonitrile to give moderate to good yields of the corresponding α-chlorocarbonyl compounds. Mixtures of α-chloro- and α,α-dichlorocarbonyl compounds were obtained for substituted acetophenones. Brominations proceeded similarly with higher yields when the hydrochloric acid was replaced with hydrobromic acid.     

1,4—双（苯基乙炔基）苯及其双取代苯基衍生物的研究

合成了1,4-双(苯基乙炔基)苯及其双取代苯基衍生物。测定了它们的荧光量子产率、激光转换效率、红外光谱、拉曼光谱,指派了主要官能团的特征频率,讨论了化合物结构和取代基效应。     

Four-wave mixing between a soliton and noise in a system with large amplifier spacing

Depletion of soliton energy by four-wave mixing between a soliton and amplifier noise in a system with 100-km amplifier spacing is studied. Dispersion exponentially decreasing fiber is used as transmission fiber. Improvement of the system by the use of a sliding-frequency filter to reduce noise power and the depletion of soliton energy is shown. The system can be further improved by compensation for depleted soliton energy.