Ascorbic Acid Oxidation at Nonmodified and Copper‐Modified Polyaniline and Poly‐ortho‐methoxyaniline Coated Electrodes

The electrochemical oxidation of ascorbate ions is comparatively studied at polyaniline (PANI) and poly‐ortho‐methoxyaniline (POMA) layers in absence and presence of electrodeposited copper species. In comparison to PANI, POMA layers allow decreasing the overpotential necessary for driving the ascorbate oxidation reaction. A nonlinear dependence of the ascorbate oxidation current on the polymer layer redox charge is found. Copper electrodeposited in PANI and POMA layers is electrocatalytically active for the investigated reaction. Two separate oxidation waves are observed in the case of Cu‐PANI whereas a single ascorbate oxidation wave and enhanced currents are found in the Cu‐POMA case.     

ACu9X4 ‐ Neue Verbindungen mit der CeNi8, 5Si4, 5‐Struktur (A: Sr,Ba; X: Si,Ge)

ACu₉X₄ ‐ New Compounds with CeNi_{8, 5}Si_{4, 5} Structure (A: Sr, Ba; X: Si, Ge) The new compounds SrCu₉Si₄ (a = 8.146(1), c = 11.629(2)Å), BaCu₉Si₄ (a = 8.198(2), c = 11.735(2)Å), SrCu₉Ge₄ (a = 8.273(2), c = 11.909(5)Å), and BaCu₉Ge₄ (a = 8.338(4), c = 12.011(7)Å) are formed by reaction of the elements at 1000° ‐ 1100 °C. They are isotypic (I4/mcm, Z = 4) and crystallize in an ordered variant of the cubic NaZn₁₃ type structure, also built up by the binary phase BaCu₁₃. In the ternary compounds the positions of Cu2 are orderly occupied by copper and silicon and germanium, respectively. This results in a lowering of symmetry and a distortion of the polyhedra. The metallic conductivity of the compounds was confirmed by measurements on BaCu₉Si₄.     

Prescriptions and Ingredients for Controlled CC Bond Formation with Organometallic Reagents. New synthetic methods (5)

Merits and drawbacks of known carbon-carbon linking procedures are outlined. Two novel methods are discussed in some detail: the copper-catalyzed alkylation of Grignard reagents and reactions with allylpotassium compounds. Both methods provide a very efficient access to saturated, unsaturated, as well as functionally substituted hydrocarbons and moreover permit an astonishing degree of regio- and stereoselective control of olefin synthesis.     

Advanced Current Collectors for Alkali Metal Anodes

High-energy-density batteries are in urgent need to solve the ever-increasing energy storage demand for portable electronic devices, electric vehicles, and renewable solar and wind energy systems. Alkali metals, typically lithium(Li), sodium(Na) and potassium(K), are considered as the promising anode materials owing to their low electrochemical potential, low density, and high theoretical gravimetric capacities. However, the problem of dendrite growth of alkali metals during their plating/stripping process will lead to low Coulombic efficiencies, a short lifespan and huge volume expansion, eventually hindering their practical commercialization. To resolve this issue, a very effective approach is engineering the anodes on structured current collectors. This review summarizes the development of the alkali metal batteries and discusses the recent advances in rational design of anode current collectors. First, the challenges and strategies of suppressing alkali-metal dendrite growth are presented. Then the special attention is paid to the novel current collector design for dendrite-free alkali metal anodes. Finally, we give conclusions and perspective on the current challenges and future research directions toward advanced anode current collectors for alkali metal batteries.     

Lewis-Base Adducts of Group 11 Metal(I) Compounds. LXXVI Structural Studies in the Copper(I) Halide : Norbornadiene System

The structural characterizations of some copper(I) halide (CuX) adducts with norbornadiene (nbd) are recorded. CuCl : nbd (1:1)₄ (a redetermination), (2:1)_2(|), are systems both based around Cu₄Cl₄ cubane-type cluster arrays. CuBr : nbd (7:3)_(|)( 0.5 MeOH), a complex polymer with 3-symmetry, is believed to be the complex previously described as an adduct of 2:1 stoichiometry. Attempts to obtain an iodide counterpart have resulted in the definition of an ephemeral adduct CuI : MeCN (3:2)_(|). 0.5 C₇H₈ in which, remarkably, the nbd is uncoordinated; the complex is a polymer, related to the [AgX(quinoline)]_(|) (X = Cl, Br) saddle polymer.     

Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for N-tert-butoxycarbonylation of amines under solvent-free conditions at room temperature

Commercially available copper(II) tetrafluoroborate hydrate was found to be a highly efficient catalyst for chemoselective N-tert-butoxycarbonylation of amines with di-tert-butyl dicarbonate under solvent-free conditions and at room temperature. Various aromatic amines were protected as their N-tert-butyl carbamates in high yields and in short times. No competitive side reactions such as isocyanate, urea, and N,N-di-t-Boc formation was observed. Chemoselective N-tert-butoxycarbonylation was achieved with substrates bearing OH and SH groups. Chiral α-amino acid esters afforded the corresponding N-t-Boc derivatives in excellent yields.     

ZnO超细纳米线阵列的制备及其电化学性能

以Zn(NO₃)₂· 6H₂O和C₆H₁₂N₄为原材料,采用二步水热法在碳纤维布上合成了形貌尺寸均匀的ZnO超细纳米线阵列。用 X 射线衍射(XRD)和扫描电镜(SEM)对其晶体结构和形貌进行了表征,利用恒流充放电测试等手段对其进行电化学性能测试。测试结果表明,材料表现出优异的电化学性能。在200 mA/g的电流密度下循环150次后,ZnO超细纳米线阵列仍然约有730 mAh/g的充放电比容量,库伦效率保持在95%以上。在1 200 mA/g的大倍率条件下,材料的充放电比容量依旧可达481 mAh/g左右,表现出十分良好的循环稳定性和可逆性能,是一种较为理想的锂离子电池负极复合材料。     

火焰原子吸收法测定氧化钼中铜、铅

本文介绍了用火焰原子吸收法测定氧化钼中铜、铅的方法,确定了两种元素最佳仪器工作条件,该方法快速、简便、准确,对试样的回收为９８．８－１０２％,样品测定的相对偏差小于１％,对实际样品了测定获得满意结果。     

Use of a Tensammetric Wave for the End-Point Detection in Chelatometry

Abstract

A new method for the end-point detection in complexometric titration using a tensammetric wave of organic reagents such as oxine and alizarin complexone (ALC) was studied. The tensammetric wave of these reagents disappears by their chelate formation and reappears by the liberation of free indicator during the exchange reaction between indicator chelate and EDTA. This mechanism is utilized for the end-point detection in complexometric titration of metals. Since the sensitivity of tensammetric wave is extremely high, very sharp end-point can be obtained for the titration of metals even in the concentration of 10^?5M.     

Synthesis,structure, spectral and magnetic properties of 4-methoxy- and 3-methylsalicylatocopper(II) complexes with 2-pyridylmethanol

The synthesis and characterization of [Cu(4-MeOsal)₂(2-pyme)₂] (1) and [Cu(3-Mesal)₂(2-pyme)₂] (2) (where 4-MeOsal?=?4-methoxysalicylate, 3-Mesal?=?3-methylsalicylate and 2-pyme?=?2-pyridylmethanol) are reported. The composition and stereochemistry as well as the mode of coordination have been determined by elemental analysis, IR, electronic and EPR spectra as well as magnetization measurements over the temperature range 1.8–300?K. The crystal structures of Cu(4-MeOsal)₂(2-pyme)₂ and Cu(3-Mesal)₂(2-pyme)₂ have been determined.