Presence Of Transition Metal Salts Research Articles

Transition Metal Ions Assisted Trimerization of Polyisocyanurate and Their Pyrolyzed Derivatives as Synergistic Electrocatalysts for Oxidation of Alcohols

We demonstrate the trimerization of polyisocyanurate nanoporous foams by reacting aromatic isocyanate in the presence of transition metal salts (NiCl2·2H2O and CoCl2·6H2O) as catalysts. The metal ions were found to accelerate the gelation of the polyisocyanurate networks. The nickel–cobalt–polyisocyanurate (Ni-Co-PIR-RT) hybrid monoliths were pyrolyzed under inert atmosphere at varying temperatures (from 600 to 1000 °C) to yield oxide and metallic forms of Ni and Co with significant carbon content. Pyrolysis of Ni-Co-PIR-RT at 600 °C (Ni-Co-PIR-600) resulted in the complete reduction of Ni and Co ions to metallic Ni and Co, whereas samples pyrolyzed at 800 °C (Ni-Co-PIR-800) resulted in the partial transformation of the metallic Ni and Co to its respective oxides. The complete transformation of metallic Co to CoO was obtained at 1000 °C (Ni-Co-PIR-1000) with a significant amount of metallic Ni and NiO. The Ni-PIR-1000 sample displayed minimal activity toward methanol oxidation reaction (MOR) with an onset potential and maximum current density of 1.44 V (vs reversible hydrogen electrode) and 0.6 mA/cm2 respectively, whereas the Co-PIR-1000 sample displayed oxygen evolution reaction (OER) at an onset potential of 1.33 V with no evident activity toward MOR in 0.1 M KOH with 0.2 M CH3OH. On the other hand, under the same conditions Ni-Co-PIR-1000 displayed 5 manifold increase in current density and reduction in onset potential by 100 mV toward MOR (with an onset potential of 1.34 V and current density 4 mA/cm2) relative to Ni-PIR-1000. The synergistic and superior activity of Ni-Co-PIR-1000 can be attributed to the combined presence of Ni, NiO, and CoO. Here, (1) Ni and NiO act as the catalysts for methanol oxidation by electrochemically transforming to NiOOH (active centers for methanol oxidation) via Ni(OH)2, (2) the presence of CoO facilitates the electrochemical generation of atomic oxygen ([O]) (an intermediate in oxygen evolution reaction and a well-known oxidizing agent) by transforming to CoOOH, the [O] formed here may be responsible for the formation of NiOOH by chemically reacting with Ni(OH)2 resulting in increased activity toward MOR.

Desulfurization of Light Distillates by Oxidation and Rectification of Gas Condensate

The possibility that a process comprising the oxidation of sulfur compounds present in gas condensate and its subsequent rectification can be used to desulfurize light petroleum fractions has been explored. Oxidation of gas condensate with hydrogen peroxide in the presence of transition metal salts followed by its rectification makes it possible to decrease the sulfur content in the gasoline and diesel fractions by 95 and 75%, respectively in the fraction, with the sulfur content of -the residual fraction (350°C–FBP) remaining almost unchanged.

Декарбоксилирование 2'-дикарбокси-5-(метил-5'индолил-3')-индолил-3-уксусной кислоты с использованием одновалентной меди

In this article a decarboxylation method based on the use of quinoline with a copper salt is discussed. Decarboxylation is the elimination of CO2 from the carboxylic group of carboxylic acids or the carboxylate group of their salts. The process is used to produce a large number of organic compounds, such classes as alkanes, alkenes, alcohols, ketones, ethers and esters. Decarboxylation plays an important role in the metabolism of living organisms, namely in the decarboxylation of amino acids. From this we can conclude that the process is important to study. Decarboxylation proceeds in different ways. The most common methods of decarboxylation includes heating in various conditions. For example, such as heating in the presence of acids and alkalis, under severe conditions with quinoline, thermal oxidation in the presence of transition metal salts, Kolbe reaction. In the procces of the CO2 removal group in relation to amino acids there are several types: α-decarboxylation, decarboxylation, associated with the trans-amination reaction and the condensation reaction of molecules. In the synthesis of substituted auxin 2'-dicarboxy-5-(methyl-5'indolyl-3')-indolyl-3-acetic acid, the yield of the product was not high. The usual heating in the presence of alkali output was less than 5%, and in this work it was decided to use other methods of decarboxylation to increase the yield of the product. The aim of the work is to improve the method of decarboxylation of carboxyindolyl substrates for increasing product yield and to compare with the result obtained by ordinary heating of this substances in the presence of alkali. At the end of the work summed up. Found the optimal conditions for the process of decarboxylation of investigated substrates. Optimal conditions chosen based on product yield. To confirm the chemical structures of the substances, 1H NMR, IR spectroscopy, and elemental analysis were used.

Highly Graphitic Mesoporous Fe,N-Doped Carbon Materials for Oxygen Reduction Electrochemical Catalysts.

The synthesis, characterization, and electrocatalytic properties of mesoporous carbon materials doped with nitrogen atoms and iron are reported and compared for the catalyzed reduction of oxygen gas at fuel cell cathodes. Mixtures of common and inexpensive organic precursors, melamine, and formaldehyde were pyrolyzed in the presence of transition-metal salts (e.g., nitrates) within a mesoporous silica template to yield mesoporous carbon materials with greater extents of graphitization than those of others prepared from small-molecule precursors. In particular, Fe,N-doped carbon materials possessed high surface areas (∼800 m2/g) and high electrical conductivities (∼19 S/cm), which make them attractive for electrocatalyst applications. The surface compositions of the mesoporous Fe,N-doped carbon materials were postsynthetically modified by acid washing and followed by high-temperature thermal treatments, which were shown by X-ray photoelectron spectroscopy to favor the formation of graphitic and pyridinic nitrogen moieties. Such surface-modified materials exhibited high electrocatalytic oxygen reduction activities under alkaline conditions, as established by their high onset and half-wave potentials (1.04 and 0.87 V, respectively vs reversible hydrogen electrode) and low Tafel slope (53 mV/decade). These values are superior to many similar transition-metal- and N-doped carbon materials and compare favorably with commercially available precious-metal catalysts, e.g., 20 wt % Pt supported on activated carbon. The analyses indicate that inexpensive mesoporous Fe,N-doped carbon materials are promising alternatives to precious metal-containing catalysts for electrochemical reduction of oxygen in polymer electrolyte fuel cells.

NITRILE COMPLEXES AS EFFECTIVE ANTIMICROBIAL ADDITIVES

Antimicrobial properties of nitrile complexes of transition metal salts were studied including the investigation of their activity in surfactants and mineral oil environments. Experiments of the polymeric complexes preparation by in-situ copolymerization of the nitrile polymers in the presence of transition metal salts and reactions of transition metal salts added to the ready polymers were performed. The dependence of the polymer complexes forming particularities on central metal atoms nature was determined.

THEORETICAL INVESTIGATION OF THERMODYNAMIC PARAMETERS OF TRANSITION METAL SALTS COMPLEXATION WITH ACRYLONITRILE-STYRENE COPOLYMER

Thermodynamic parameters of formation reactions of polymer complexes of transition metals (ZnCl2, CuCl2, NiCl2, СоС12) were obtained using the PBE96/SVP computational level. Chemical processes taking place during both direct copolymerizations in the presence of transition metal salts and at introduction of transition metal salts at final step of polymerization were considered. The success of formation reaction of polymer complexes was theoretically based with the radical polymerization into solutions of transition metal salts in the presence of zink chloride only.

Tripod-type 2,2′-bipyridine ligand for lanthanide cations: synthesis and photophysical studies on coordination to transition metal cations

New tripod-type 2,2′-bipyridine ligand consisting of a central polyaminocarboxylic moiety for the coordination to lanthanide cations and three appended 5-phenyl-2,2′-bipyridine fragments for the coordination to various transition metal cations have been prepared. A europium complex of this ligand was prepared, and its photophysical properties and a luminescent response towards transition metal salts (particularly, CdI2, Cd(OAc)2, Zn(ClO4)2, Cu(OAc)2, and HgCl2) have been studied. Europium cation luminescence quenching in the presence of transition metal salts in solution was observed in all cases. In addition, it was observed that the fluorescent response of the europium complex was quite individual depending on the type of the metal salt. The obtained data were compared with the earlier published data for some lanthanide complexes bearing additional sites for the chelation of transition metal cations.

Oxidative Functionalisation of Cyclanes in the Presence of Transition Metal Salts

Oxidative Functionalisation of Cyclanes in the Presence of Transition Metal Salts

Oxidative Functionalisation of Cyclanes in the Presence of Transition Metal Salts

Oxidative Functionalisation of Cyclanes in the Presence of Transition Metal Salts

Inhibiting effects of transition metal salts on methane hydrate stability

The behavior of clathrate hydrates in the presence of transition metal salts was investigated using a Differential Scanning Calorimeter (DSC). Specifically, a DSC was employed to determine the onset temperature for methane hydrate decomposition in the presence of ferric chloride hexahydrate, [FeCl2(H2O)4]Cl·2H2O, anhydrous ferric chloride, FeCl3, MnSO4, FeSO4, CuSO4, and AgNO3, and to compare the inhibiting properties of these transition metal salts with NaCl and CaCl2, two well-known salt inhibitors. The degree of methane hydrate inhibition induced by the salts that were studied (as indicated by the reduction in dissociation temperature at a given pressure), when compared between mixtures with the same mole percentages of the salt, increases in the following order: FeSO4≈CuSO4<MnSO4≈AgNO3≈CaCl2<NaCl<FeCl3. A smaller decrease in the dissociation temperature was observed with salts that contained the larger sulfate anion when compared to salts that contained the smaller chloride anion. Smaller decreases in the dissociation temperature were observed with salts that contained smaller cations like Fe2+ when compared to salts that contained larger cations such as Ag+ and Mn2+. It is posited that the interaction between water with salt ions results in hydrate formation inhibition and the strength of the salt ion-dipole bond between the metal ion and water molecules correlates with the degree of inhibition. Consideration of the charge and size characteristics of the anion and cation components of the tested salts appears to explain this behavior.

Improved synthesis of polycarbynes

Two polymers of the polycarbyne family, namely poly(hydridocarbyne) and poly(phenylcarbyne), were synthesized by the magnesium-assisted reductive condensation of organic gem-trihalides in the presence of transition metal salts under mechanical activation.

Convenient and Efficient Method for the Synthesis of Phthalocyanines and Metallophthalocyanines in Task-Specific 2-Hydroxyethyl Ionic Liquids

Tetramerization of substituted phthalonitriles in task-specific 2-hydroxylethyl-based imidazolium and ammonium ionic liquids at 100 °C gave corresponding phthalocyanines in moderate yield. Further the reaction of substituted phthalonitriles in the presence of transition-metal salts in ionic liquids gave the corresponding metallophthalocyanines. The 2-hydroxylethyl ammonium ionic liquids gave better yields of phthalocyanines than 2-hydroxylethyl imidazolium and nonhydroxyl functionalized ionic liquids. The isolation and separations of different phthalocyanines were accomplished by silica-gel column chromatography, and products were characterized by various spectroscopic techniques.

Selective oxidization of 2- and 3-aminotoluene by ozone in the glacial acetic acid to the corresponding aminobenzoic acids

The kinetic regularities and mechanisms of oxidation reactions of 2- and 3-aminotoluene and its acylation derivatives by the gases that contain ozone in the glacial acetic acid have been studied. It has been established that ozone attacks mainly the lone pair of electrons of the nitrogen atom with formation, mainly, of polymers of azo compounds. The products oxidation on methyl group are not formed in these conditions. The direction of the ozone’s attack can be altered and directed on the methyl group, as well as by an aromatic ring, by acylation of the amino group. The total yield of the products of oxidation of the methyl group of 2- and 3-acetamidotoluene is 5,1 and 12,4 % respectively. The process of liquid-phase catalytic oxidation of 2- and 3-acetamidotoluene by the ozone in the presence of transition metal salts and their mixtures with potassium bromide to the corresponding acetamidobenzoic acids has been investigated as well. At the presence of acetate Co (II) the output of 2- and 3-acetamidobenzoic acid 25,0 and 31,2% respectively. We found out that the use of our catalytic system (ozone – acetamidotoluene - Co (III) – glacial acetic acid - potassium bromide) significantly increases the reaction rate and the selectivity of sub­strate oxidation of methyl groups. The main product of oxidation of 2- and 3-acetamidotoluene becomes 2- and 3-acetamidobenzoic acid (55,0 and 71,2 % respectively). Replacing ozone-air mixture with the ozone-oxygen mixture leads to higher yield of 2-acetamidobenzoic acid 70,0 % and 3- acetamidobenzoic acid 86,0 %.

A Regioselective Synthesis of Multi-Substituted 2-Imino-1,3-oxazolines by One-Pot Reaction

Heterocycles are significant chemical entities for research on small molecule drugs and their development in the pharmaceutical industry. Attention until now has focused on synthetic methods for forming heterocycles. However, new and efficient synthetic methods for the construction of heterocyclic molecules are now being researched continuously. In our previous papers, we reported the construction of two different combinatorial libraries, including novel 2imino-1,3-thiazolines 1, that show T-type calcium channel inhibitory activity and fungicidal property. Recently, a number of reports examined the significant biological activities of the 2-imino-1,3-thiazoline derivatives. As an extension of our efforts to investigate the biological activities of their analogues, we synthesized 2-imino-1,3-oxazolines 2, which are isosteres of 2-imino-1,3-thiazolines 1 (Figure 1). In the present study we investigate a method for synthesizing multi-substituted 2-imino-1,3-oxazolines 2 with the aim of increasing the diversity in chemical structures. A comparison of the biological activity of 1 and 2 promises to increase our understanding of the structure-activity relationship of this series. A literature survey revealed few reports on the synthetic methods of 2-imino-1,3-oxazolines. The synthetic methodologies of 2-imino-1,3-oxazolines reported over the past three decades were classified into four categories. First, a condensation of α-haloketone and symmetrical diphenylurea in presence of bromine as the condensing agent gave 2-arylimino-3-aryl-1,3-oxazolines. Second, electrochemical synthesis of substituted phenylmonoimine with N-acylcarbonimidoyl dichloride resulted in tetraaryliminooxazolines. Third, the reaction of ketenimine with hydroxylamino derivatives gave 2-imino-1,3-oxazolines through 3-iminoisoxazolines. Fourth, the reaction of alkyl diazoacetates with carbodiimides in presence of transition metal salts gave 2-imino-1,3-oxazoline derivatives. Unfortunately, all these reported methods suffered the limitations of low yield, harsh reaction conditions, and lack of regioselectivity and chemical structural diversity of the products. Therefore, we herein report a very simple and convenient synthetic method for the preparation of multi-substituted 2-imino-1,3-oxazolines derivatives with the aim of increasing the product diversity and production yield, by reacting α-hydroxyketone and carbodiimide in the presence of copper salts as a catalyst.

The amplification of polymerized diaminobenzidine with physical developers: sensitizing effects of transition metal salts and sulphide

Amplification of metal-complexed polymerized diaminobenzidine by two light-insensitive physical developers was systematically examined in a dot blot model system following either polymerizing diaminobenzidine in the presence of transition metal salts or applying the metal salts post-diaminobenzidine polymerization. The effect of sodium sulphide treatment on subsequent amplification was also investigated. Those metal-diaminobenzidine complexes that facilitated the most powerful amplification were subsequently tested in an immunohistochemical setting. The most dramatic amplification of polymerized diaminobenzidine was observed following its post-polymerization treatment with salts of platinum alone, or gold or vanadium with subsequent sulphide treatment, and allowed previously invisible quantities of polymerized diaminobenzidine to be clearly seen. Three other transition metal salts also improved the amplification of polymerized diaminobenzidine but to a lesser degree, namely nickel alone, and silver or rhodium with subsequent sulphide treatment. Sensitivity was comparable with the colloidal gold-silver amplification system.

Synthesis of 2,3-acetylenic amines by aminomethylation of acetylenes with geminal diamines

A general and effective procedure has been developed for the synthesis of symmetrical and unsym- metrical 2,3-acetylenic amines by aminomethylation of terminal mono- and diacetylenes with geminal diamines in the presence of transition metal salts and complexes.

Antenna Chemistry with Metallic Single-Walled Carbon Nanotubes

We show that, when subjected to microwave fields, surfactant-stabilized single-walled carbon nanotubes (SWNTs) develop polarization potentials at their extremities that readily drive electrochemical reactions. In the presence of transition metal salts with high oxidation potential (e.g., FeCl3), SWNTs drive reductive condensation to metallic nanoparticles with essentially diffusion-limited kinetics in a laboratory microwave reactor. Using HAuCl4, metallic particles and sheaths deposit regioselectively at the SWNT tips, yielding novel SWNT-metal composite nanostructures. This process is shown to activate exclusively metallic SWNTs; a degree of diameter selectivity is observed using acceptors with different oxidation potentials. The reaction mechanism is shown to involve Fowler-Nordheim field emission in solution, where electric fields concentrate at the SWNT tips (attaining approximately 10(9) V/m) due to the SWNT high aspect ratio (approximately 1000) and gradient compression in the insulating surfactant monolayer. Nanotube antenna chemistry is remarkably simple and should be useful in SWNT separation and fractionation processes, while the unusual nanostructures produced could impact nanomedicine, energy harvesting, and synthetic applications.

Oxidation of Alkylaromatics

Hydroperoxide atα-position to the aromatic ring is the primary oxidation product formed. In all cases monoalkylbenzenes lead to the formation of benzoic acid. Oxidation in the presence of transition metal salts not only accelerate but also selectively decompose the hydroperoxides. Alkyl naphthalenes mainly produce the corresponding naphthalene carboxylic acids. Hock-rearrangement by the influence of strong acids converts the hydroperoxides to hemiacetals. Peresters formed from the hydroperoxides undergo Criegee rearrangement easily. Alkali metals accelerate the oxidation while CO2as co-oxidant enhances the selectivity. Microwave conditions give improved yields of the oxidation products.

Electrospray Ionization Mass Spectrometry (ESI-MS) as a Useful Tool for Fast Evaluation of Anion and Cation Complexation Abilities of a Cyclam Derivative

Electrospray ionization mass espectrometry (ESI-MS) has been used for the study of a cyclam derivative noncovalent interactions. At acidic pH, diprotonated macrocycle bound to different anionic species were observed. The selectivity shown by competitive experiments is rationalized with the help of semiempirical theoretical calculations. At basic pH, the base peak corresponded to the macrocycle-alkaline metal complexes, and again competition experiments showed different binding strength. Finally, experiments carried out in the presence of transition metal salts allowed the detection of the complexes present in the mixture and revealed their different kinetic behavior.

Transition Metal Modified TiO2-Loaded MCM-41 Catalysts for Visible- and UV-Light Driven Photodegradation of Aqueous Organic Pollutants

A number of transition metal (Cr, V, Fe, Cu, Mn, Co, Ni, Mo, and La) incorporated MCM-41 mesoporous molecular sieves with Si/Me = 80 have been synthesized by a hydrothermal method. It was demonstrated that the presence of transition metal salts in the gel during synthesis hinders the action of the template, which results in pores of MCM-41 that are not well-formed. These materials were then loaded with TiO2 via the sol−gel method, and the resulting materials were explored for the destruction of 4-chlorophenol in the presence of visible, as well as UV, light. A combination of various physicochemical techniques such as N2 physisorption, O2 chemisorption, X-ray diffraction (XRD), diffuse reflectance UV−vis (DR UV−vis), and temperature program reduction (TPR) were used to characterize the chemical environment of these transition metals in the prepared catalysts. The dispersion of transition metals as determined by O2 chemisorption suggests that they are well dispersed inside the MCM-41 framework, but the disp...