Electrochemical study of triphenyltin piperidyl dithiocarbamate

The reduction of triphenyltin piperidyl dithiocarbamate in acetone has been investigated using d.c. polarography and cyclic voltammetry. Polarographic reduction yielded four well-defined waves, two of which were diffusion-controlled and two of which appear to represent adsorption processes. The cyclic voltammetric study yielded results in close agreement with the polarographic data. Results appear to indicate the release of the dithiocarbamate moiety, followed by reduction to form the triphenyltin radical, which undergoes dimerization, as well as reduction to the triphenyltin anion. For comparison, the polarographic reduction of triphenyltinchloride was investigated. A mechanism similar to that proposed by earlier authors for the polarographic behaviour of tributyltin oxide was found. For convenience, the more commonly used terminology of piperidyl dithiocarbamate is used throughout the paper, in place of (piperidine-1-carbodithioato) triphenyltin (IV).     

Synthesis,Characterization and Magnetic Properties of New Dinuclear Copper(II) Complexes with N,N′‐Disubstituted Dithiooxamides derived from α‐Amino Acids

Four new dinuclear copper(II) complexes have been synthesized and have the general formula [Cu₂(L)(H₂O)₂], where L = GLYDTO [N,N′‐bis(carboxymethyl)dithiooxamide], ALADTO [N,N′‐bis(carboxyethyl)dithiooxamide], VALDTO [N,N′‐bis(1‐carboxy‐2‐methylpropyl)dithiooxamide] and LEUDTO [N,N′‐bis(1‐carboxy‐3‐methylbutyl)dithiooxamide]. The complexes were characterized by elemental analysis as well as by IR, electronic and EPR spectroscopy. These techniques provided evidence for the presence of the CuNO₂S chromophore. Magnetic susceptibility measurements on all the complexes in the range 4–300 K show the existence of a dominant antiferromagnetic interaction with ?J values greater than 300 cm^?1. Thermal decomposition behaviour of the complexes was studied by thermogravimetry.     

Electrical Behavior of New Orthophosphates Na2M3(PO4)3 (M3=GaMn2, GaCd2, InMn2 and FeMnCd) with Alluaudite-Like Structure

New sodium orthophosphates of general formula Na₂M₃(PO₄)₃ belonging to the alluaudite-type structure have been synthesized and characterized by neutron and X-ray powder diffraction. The nature of the M₃ elements (M₃=GaMn₂, GaCd₂, InMn₂ and FeMnCd) was chosen in order to analyze their influence on electrical and magnetic properties. The conductivity of these materials was measured by the complex impedance method and the transport mechanism was studied from complex permittivities and modulus formalism. Electrical results including charge/discharge experiments showed two main behaviors: GaCd₂ and FeMnCd behave as purely ionic conductors whereas GaMn₂ and InMn₂ are mixed ionic-electronic conductors. The magnetic susceptibility data reveal the antiferromagnetic behavior of FeMnCd, InMn₂ and GaMn₂, with a weak ferromagnetic transition at low temperatures.     

层状锑磷酸嵌接式卟啉锰制备与模拟细胞色素氧化催化研究

层状锑磷酸嵌接式卟啉锰制备与模拟细胞色素氧化催化研究胡希明，皮宗新，梅治乾，古国榜，黄仲涛（华南理工大学应用化学系，华南理工大学化学工程系，广州，５１０６４１）关键词卟啉锰，层状锑磷酸，嵌接，催化性能细胞色素Ｐ４５０是一种含血红素的单充氧化酶，在室温...     

Electrochemical behaviour of an indium electrode in concentrated KOH solutions at different temperatures

Summary The electrochemical behaviour of pure indium in KOH solutions (1–4M) was studied at different temperatures (25–70°C) by potentiostatic techniques. Two anodic peaks corresponding to the formation of In(OH)₃ and In₂O₃ were observed. The heights of the two peaks increased with the increase of alkali concentration. An increase of temperature increased the peak currents and shifted their corresponding potentials to more negative values. The variation of the peak currents and peak potentials with scan rate suggested that the anodic dissolution of indium was a diffusion controlled process. In cyclic voltammetry, the reverse scan consistently showed one peak which was attributed to the reduction of anodic oxidation products into indium. X-ray diffraction analysis confirmed the presence of In(OH)₃ at the first anodic peak, In(OH)₃ and In₂O₃ at the second anodic peak and In₂O₃ in the permanent passive region.

---

Zum elektrochemischen Verhalten einer Indium-Elektrode in konzentrierter Kalilauge bei verschiedenen Temperaturen

Zusammenfassung Es wurde das Verhalten von reinem Indium in 1 – 4M KOH-Lösungen bei Temperaturen zwischen 25 und 70°C mittels potentiostatischer Methoden untersucht. Zwei anodische Peaks, entsprechend der Bildung von In(OH)₃ und In₂O₃, traten auf. Die Höhe der beiden Peaks wurde mit zunehmender Alkalikonzentration gesteigert. Eine Temperaturerhöhung verstärkte die Peakströme und verschob die entsprechenden Potentiale zu negativeren Werten. Die Abhängigkeit der Peakströme und Peakpotentiale von der Scangeschwindigkeit legte den Schluß nahe, daß die anodische Lösung von Indium in einem diffusionskontrollierten Prozeß stattfindet. Bei der cyclischen Voltammetrie zeigte der reverse Scan einheitlich einen Peak, der der Reduktion der anodischen Oxidationsprodukte zu Indium zugeschrieben wurde. Röntgendiffraktionsanalyse bestätigte die Präsenz von In(OH)₃ beim ersten anodischen Peak, In(OH)₃ beim zweiten Peak und In₂O₃ im permanent passiven Bereich.

     

Degradation Kinetics of an Epoxy/Cycloaliphatic Amine Resin Under Isothermal and Non-isothermal Conditions

A study of an epoxy-cycloaliphatic amine system has been realized using a thermogravimetric technique (TG). Isothermal and non-isothermal (dynamic) methods were employed to determine the kinetic data of this system. Five methods were used for determining the activation energies of this system in the dynamic heating experiments. In two of them (Flynn-Wall-Ozawa, and Kissinger) it is not necessary to have a prior knowledge of the reaction mechanism of the degradation behaviour for this system. In the other ones (Coats and Redfern, Horowitz and Metzger, and Van Krevelen et al.) it is necessary to know this reaction mechanism, besides Criado et al. method was used for determining it. The results have shown that good agreement between the activation energies obtained from all methods can be achieved if it is assumed that the degradation behaviour of this system is of sigmoidal-rate type. This revised version was published online in August 2006 with corrections to the Cover Date.     

The drawing behavior of Y-Ba-Cu-O sol from non-aqueous solution by a complexing process

A complexing process is developed to prepare Y-Ba-Cu-O superconducting fibers. The process is not identical to typical sol-gel processes; here the resulting gel network is built up by hydrogen bonding linkage among complexing species in non-aqueous solution. Cu acetate, [Cu(OAC)₂], Ba methoxyethoxide [Ba(ORE)₂] and Y acetate [Y(OAC)₃] are used as precursors for preparing homogeneous gels while -methacrylic acid (HOAA) and diethylenetriamine (DETA) as complexing agents, and methoxyethanol (REOH) as solvent. Fibers drawn from a sol obtained through reduced pressure present no or little deformation at 80°MoC via adjusting the amount of DETA and HOAA. Cu(OAC)₂, Ba(ORE)₂ and Y(OAC)₃ in the complexing process have been demonstrated to form gels without hydrolysis and condensation at ambient atmosphere. The relationships between the drawing behavior of sols and gel structure with different amounts of DETA and HOAA are suggested. The concentration region of drawing the gel fibers with no or little deformation heated at 80°MoC is also found.     

Spin-transition behaviour of transition metal complexes with 2,6-bis-(benzimidazol-2′-yl)-pyridine induced by deprotonation of the complex

Summary 2,6-bis-(Benzimidazol-2-yl)-pyridine (bzimpy = H₂ L) acts as a bidentate ligand when combining with transition metal ions. The complexes [M(bzimpy)₂](ClO₄)₂ (M = Fe²⁺, Mn²⁺, Zn²⁺, Co²⁺, and Ni²⁺) were obtained as solids. The protonation constants (logK) for the ligand and the complexes were evaluated in 30:70 (v/v) H₂O:EtOH at 293 K and at constant ionic strength of 0.12M KCl. Coordination of the ligand to the metal ions leads to an increase of acidity of the imino-hydrogen of the benzimidazole group of the ligand as a function of the complex stability. Deprotonation leads to a spin-state transition (intermediate spin-state low-spin) of the iron(II)-complex, followed by a shift of the metal-to-ligandcharge transfer band (MLCT) to lower energies (_max=563 to 580 nm). The d-d absorption bands are found to shift to higher energies and the low-spin isomer is favoured at room temperature. An opposite shift of theMLCT band (_max=563 to 557 nm) is observed when HClO₄ is added to the complex solution, rendering the high-spin state of the complex more favourable.On leave from the Chemistry Department, Jahangirnagar University, Dhaka, Bangladesh     

Synthesis, characterisation and thermal behaviour of solid state compounds of 4-methylbenzylidenepyruvate with some bivalent metal ions

Solid state M-4-Me-BP compounds, where M stands for bivalent Mn, Fe, Co, Ni, Cu, Zn, Pb and 4-Me-BP is 4-methylbenzylidenepyruvate, have been synthesized. Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, elemental analysis, and complexometry were used to characterise and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, thermal stability and thermal decomposition of the isolated complexes.     

微圆盘电极上耦合—级均相反应的稳态电流

在电极袭面反应物浓度均匀的近似假设下,得到了微圆盘电极上暂态可逆反应的一般解.然后利用该一般解得到了微圆盘电极上耦合一级均相反应的可逆电极反应CE、EC、EC′和ECE 的稳态电流计算公式.