Solvent-assisted mechanochemical synthesis of metal complexes

The application of solvent-assisted mechanochemical synthesis to the study of metal complex formation is illustrated by examples involving complexes of silver halides with ethylenethiourea.     

Electrochemistry of metal adlayers on metal chalcogenides

Electrodeposition of metal adlayers on semiconductor metal chalcogenides (CdSe, CdS, PbTe, PbSe, PbS, Bi₂Te₃) is reviewed. Cathodic underpotential deposition of metal adlayer on metal chalcogenide is the electrochemically irreversible surface limited reaction. The irreversibility of the upd increases in the row from tellurides to selenides and further to sulfides. The underpotential shift on chalcogenide nanoparticles increases with particle size. Metal upd on chalcogenides is applied as a means of measurement of electroactive surface area of chalcogenide electrodes. The method is especially advantageous for multicomponent systems with other component not supporting upd, such as CdSe-TiO₂, CdSe-ZnO. Differences of voltammetric profiles of Pb upd on Bi₂Te₃ and Te are applied for detection of Bi₂Te₃ surface contamination by elemental tellurium. The further tasks in the electrochemistry of metal adlayers are their incorporation as interlayers in layered chalcogenides and electrodeposition of superlattices.

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The role of short-range diffusion in solvent-assisted mechanochemical synthesis of metal complexes

The role of short-range diffusion in solvent-assisted mechanochemical synthesis is demonstrated in studies of a polymorphic transition and a ligand dissociation reaction involving copper(I) thiocyanate complexes.     

准二维金属硫属化合物类石墨烯结构的化学合成与组装

无机类石墨烯属于准二维纳米结构体系,因其具有比纯碳石墨烯本身更多的调控参数,比如带隙类型及其带隙宽度可调节等,在电子器件构筑和能量转化存储等领域有着重要的科学意义和广阔的应用前景．近年来,具有准二维特征的金属硫属化合物（metalchalcogenides,MCs）作为类石墨烯结构的重要材料体系受到了广泛关注．本文概述了近年来金属硫属化合物类石墨烯结构的化学制备方法及其可能的组装应用,提出了通过系列方法影响层间作用力及利用晶体各向异性等材料设计与合成策略来实现类石墨烯的化学合成,并展望了类石墨烯的组装结构在能量存储与智能传感领域的应用前景．     

Room temperature synthesis of coinage metal (Ag, Cu) chalcogenides

Coinage metal chalcogenides in their nanoregime have been synthesized in aqueous medium at room temperature by mixing the nanoparticles of silver or copper with selenium nanoparticles which are authenticated by UV-vis, XRD and TEM analyses.     

Cluster synthesis via ligand-arrested solid growth: triethylphosphine-capped fragments of binary metal chalcogenides

A new and potentially highly generalizable technique for synthesizing molecular fragments of binary solids is demonstrated through application to selected transition metal chalcogenides. Employing a metal atom reactor, the solids are evaporated with a tungsten heating boat, and the resulting vapor is co-condensed with triethylphosphine. Major cluster products identified from a survey of first-row transition metal sulfides include the known species Cr6S8(PEt3)6, Co6S8(PEt3)6, and Cu12S6(PEt3)8, as well as the unprecedented species Fe4S4(PBun3)4, Ni4S4(PEt3)8, and Cu6S4(PEt3)4. Reactions utilizing Cu2Se resulted in the much larger clusters Cu26Se13(PEt3)14 and Cu70Se35(PEt3)21. The core of the former has a Th-symmetry structure featuring a body-centered icosahedron of Se2- anions, while the latter adopts a triangular structure based on three hexagonal closest packed layers of Se2- anions. In both cases, the Cu+ cations occupy distorted tetrahedral or trigonal planar sites similar to those encountered in Cu2Se; however, emergence of the face-centered cubic anion lattice of the bulk solid is not yet apparent at these cluster sizes.     

Use of ionic liquids in the synthesis of nanocrystals and nanorods of semiconducting metal chalcogenides

We have synthesized nanoparticles of hexagonal CdS in the diameter range 3-13 nm by the reaction of cadmium acetate dihydrate with thioacetamide in imidazolium [BMIM]-based ionic liquids. We have obtained three different particle sizes of CdS by changing the anion of the ionic liquid. Addition of trioctylphosphine oxide (TOPO) to the reaction mixture causes greater monodispersity as well as smaller particle size, while addition of ethylenediamine produces nanorods of 7 nm average diameter. Hexagonal ZnS and cubic PbS nanoparticles with average diameters of 3 and 10 nm, respectively, have been prepared by the reaction of the metal acetates with thioacetamide in [BMIM][BF4]. Hexagonal CdSe nanoparticles with an average diameter 12 nm were obtained by the reaction of cadmium acetate dihydrate with dimethylselenourea in [BMIM][BF4]. In this case also we observe the same effect of the addition of TOPO as in the case of CdS. Addition of ethylenediamine to the reaction mixture gives rise to nanorods. ZnSe nanowires with a cubic structures, possible diameters in the range 70-100 nm by the reaction of zinc acetate dihydrate with dimethylselenourea in [BMIM][MeSO4]. The nanostructures obtained are single crystalline in all the cases. Most of the nanostructures show characteristic UV/Vis absorption and photoluminescence emission spectra. The thermodynamically most stable structures are generally produced in the synthesis carried out in ionic liquids.     

Phosphine-free synthesis of metal chalcogenide quantum dots by means of in situ-generated hydrogen chalcogenides

We proved that various organic solvents react with elemental chalcogens (sulfur and selenium) by liberating hydrogen chalcogenide (H₂X, X = S, Se) during the phosphine-free hot-matrix synthesis of quantum dots. The in situ-produced H₂X reacts further with the metal salt to form the corresponding nanosized metal chalcogenide CdX. The effect of temperature on the rate of H₂X generation was quantitatively studied in various organic solvents. We found that the organic amines reduce the reaction temperature of the phosphine-free quantum dots synthesis, being more effective in situ generators of H₂S than the other tested organics at relatively low temperatures (140–170 °C).     

几种卟啉及其配合物合成方法的改进

本文首先改进了meso位有强推电子基团的四-[4-(N,N-二甲基)苯胺基]卟啉(TDMAPPH~2)的合成方法.在此基础上, 改进了最近报道的一种新型水溶性卟啉四-[4-(N,N,N-二甲基, 丙磺酸基)苯胺基]卟啉(TDMAPPTPSH~2)的合成, 进而合成了系列水溶性金属卟啉(M'TDMAPPTPS, M'=Co,Cu,Zn,Mg,Mn,Ni).并由IR,UV-vis光谱法和元素分析得到确证.     

Effects of various atmospheres and some metal oxide additives on the thermal decomposition on ammonium chromate

The thermal decomposition of ammonium chromate (AC) in dynamic air, CO₂ and N₂ and in static atmospheres and in the presence of MoO₃, V₂O₅, Fe₂O₃, CuO, MnO₂ and Nd₂O₃ additives was studied by means of TG, DTA, IR spectroscopy and electrical conductivity measurements. It was found that AC decomposes in four stages, forming unstable intermediates which produce Cr₂O₃ as a final product. The presence of the different atmospheres and the oxide additives affected the decompositions of these intermediates and the oxidation state of the chromium ions. Finally, the mechanisms associated with the different decomposition stages are discussed.     

Solid-state mechanochemical synthesis of ferrocene

Solid-state mechanochemical reactions of iron(II) chloride with cyclopentadienides of alkaline metals or thallium, which lead to the formation of ferrocene, were studied. The dependence of the yield of the product on the parameters of mechanical loading for the reaction with cyclopentadienylthallium was determined.     

Solvent-free mechanochemical Buchwald-Hartwig amination of aryl chlorides without inert gas protection

A solvent-free Buchwald-Hartwig amination had been developed under high-speed ball-milling conditions, which afforded the desired products with moderate to high yields. The addition of sodium sulfate was found to be crucial for improving both the performance and the reproducibility. Comparative solvent-free stirring experiments implicated the importance of mechanical interaction for the transformation, and the inert gas was proved to be unnecessary for this amination.     

The effect of high intensity ultrasound on the synthesis of some polyurethanes

High intensity ultrasound has been applied to the preparation of polyurethanes from a number of diisocyanates and diols. In all cases, the sonochemical reactions proceeded faster in the early stages and led to higher molecular weight polymers. The effect of changing the ultrasound intensity is discussed and some speculation as to the mechanism of the reaction enhancement is given.     

Synthesis and properties of low-dimensional metal chalcogenides

The search of new one-dimensional (1D) conducting compounds cannot be conducted only from geometrical considerations, for example, by looking at the various ways to associate coordination polyhedra to form chains. Two other conditions must be fulfilled: a condition external to the chain that implies that they be stable with respect to one another, in relation with a certain ionicity of the network, and an internal condition on cation-cation direct interaction to obtain metallic conductivity. A more empirical way to start with consists in considering the charge density wave type phenomenon and to see the various possible evolutions from a given material. These considerations are illustrated on the basis of a continuous evolution from di- to trichalcogenides, then halogenotetrachalcogenides, doped materials, and finally waved 1D compounds.     

Solvent-free mechanochemical synthesis of diacylfuroxans

Acetophenones with a variety of substituents could be converted to diacylfuroxans in a solvent-free reaction by combining the reagents Fe(NO₃)₃·9H₂O and P₂O₅ under high-speed ball milling. This reaction was facile and eco-friendly, and exhibits advantages in terms of better toleration, safety, and easier operation. The nitrate acid and nitrogen dioxide generated in situ should play a major role in this mechanochemical reaction.     

The effect of additives on organolithiums

The effect of additives on the “apparent” acidities of weak carbon acids as measured versus lithiated amides is found to be small (< 2 pK units). TMEDA is found to be the most effective in accelerating the rates of deprotonation of triphenylmethane.     

Investigation of some chalcogenides with spinel structure

The unusual combination of magnetic, semiconducting, and optical properties of the chalcochromites and other chalcogenide phases with spinel structure AB₂X₄ has attracted considerable attention for researchers (1–3). Although the physics of magnetic semiconductors is based on highly developed theoretical models and numerous experiments, the physical chemistry of these materials has many gaps. Knowledge of the thermal stability of the chalcogenide spinels, of the equilibrium conditions of their formation, and of their thermodynamics is lacking, although extremely important for the synthesis and thermal processing of single crystals and polycrystalline materials of the AB₂X₄ type. This paper presents the results of a study of the thermal stability and thermochemical, thermodynamic, and crystallochemical properties of the chalcochromites MeCr₂X₄ (Me = Cd, Co, Zn, Fe, Cu; X = S, Se, Te), thiocobaltites MeCo₂S₄ (Me = Cu, Co), thiorhodites Me_xRh_3−xS₄ (Me = Cu, Co, Fe), thioaluminates MeAl₂S₄ (Me = Zn, Cr), and solid solutions based on these. An attempt is made to show how much the investigated properties influence the magnetic and electrical properties of the chalcogenide spinels. This work is a continuation of the systematic investigation of chalcospinels, including, in particular, nonstoichometry and defect formation in the chalcochromites (4–7) homo- and heterovalent replacement in the chalcochromites (6, 8), and compound chalcochromites with replacement in the cation sublattice (9–11).     

Application of the zone melting technique to metal chelate systems-V Zone chromatographic separation of metal chelates on columns of some inert solid solvents

Binary mixtures of acetylacetone and 8-hydroxyquinoline chelates of copper(II), nickel(II), cobalt(II) and cobalt(III) were processed by zone-chromatography on columns of some naphthylalkyl ethers as inert solid solvents. The metal chelates were separated to give chromatograms on the columns according to the ratio of their distribution coefficients. Distribution coefficients of metal ions varied with the type of chelating agent used and the solid solvent, and were found to be strongly affected by operating conditions, especially zone length, zone travelling speed and initial concentration of the metal chelate.     

Thermogravimetric studies on catalytic effect of metal oxide nanoparticles on asphaltene pyrolysis under inert conditions

This study investigated the catalytic effect of NiO, Co₃O₄ and Fe₃O₄ nanoparticles toward asphaltene thermal decomposition (pyrolysis) under inert conditions. Asphaltene adsorbed onto the selected nanoparticles were subjected to thermal decomposition up to 800?°C in a thermogravimetric analyzer. The presence of nanoparticles caused a significant decrease in the asphaltene decomposition temperature and activation energy. Activation energies for the process were calculated using the Ozawa?CFlynn?CWall method. All the selected metal oxide nanoparticles showed high catalytic activity toward asphaltene decomposition in the following order NiO?>?Co₃O₄?>?Fe₃O₄. This study confirms that metal oxide nanoparticles can significantly enhance the thermal decomposition of heavy hydrocarbons, like asphaltenes.