A magnetically recoverable copper–salen complex as a nano-catalytic system for amine protection via acetylation using thioacetic acid

Research on Chemical Intermediates - A novel copper(II)–salen complex was immobilized on the surface of magnetite nanoparticles using chitosan as a linker. This system exhibits superior...     

Sulfamic acid immobilized on amino‐functionalized magnetic nanoparticles: A new and active magnetically recoverable catalyst for the synthesis of N‐heterocyclic compounds

Sulfamic acid immobilized on amino‐functionalized magnetic nanoparticles (MNPs/DETA‐SA) was successfully fabricated and characterized using various techniques. Diameters of approximately 15 nm for the MNPs/DETA‐SA were observed from scanning electron microscopy images. The as‐fabricated nanocomposite was applied as an efficient and magnetically reusable catalyst for the synthesis of 2,3‐dihydroquinazoline‐4(1H)‐one and polyhydroquinoline derivatives. All products were obtained in good to excellent yields. Recovery tests confirm that the catalyst can be readily recovered using an external magnet and reused many times without significant loss of its catalytic activity.     

Sulfuric acid heterogenized on magnetic Fe3O4 nanoparticles: A new and efficient magnetically reusable catalyst for condensation reactions

Immobilized sulfuric acid on magnetic Fe₃O₄ nanoparticles (Fe₃O₄ MNPs‐OSO₃H) as a new solid acid nanocomposite was successfully synthesized and its catalytic activity in a series of condensation reactions was studied. High catalytic activity, simple separation from reaction mixture by an external magnet and good reusability are several eco‐friendly advantages of this catalytic system. It is noteworthy that this catalytic system is applicable to a wide range of spectrum of aromatic aldehydes, and the desired products were obtained in good to excellent yields under mild conditions. The use of ecofriendly solvents makes also this synthetic protocol ideal and fascinating from the environmental point of view.     

Kinetic study of carbothermal reduction of zirconia under vacuum condition

Journal of Thermal Analysis and Calorimetry - In this research, formation mechanism and kinetics of vacuum carbothermal synthesis of zirconium carbide using zirconium acetate and sucrose are...     

Highly stable asymmetric supercapacitors based on Ni(OH)<Subscript>2</Subscript> deposited on electro-etched carbon paper

Herein, we introduce the application of nickel hydroxide nanosheets on the electro-etched carbon fiber (ECF) formed via a direct electrodeposition, for fabrication of asymmetric supercapacitor. To confirm the practical applicability of prepared Ni(OH)₂–ECF, an asymmetric device was assembled using Ni(OH)₂–ECF in combination with an activated carbon (AC) electrode. Our results showed a substantial cycling stability (96% capacitance retention after 10000 cycles) and considerable rate capability at large discharge currents (60% capacitance retention at 8 A g^??1) for this asymmetric supercapacitor that may have originated from the good contact between Ni(OH)₂ and ECF. A maximum specific capacitance of 88.1 F g^??1 was achieved for Ni(OH)₂–ECF//AC/CF device and showed considerable rate capability at large discharge currents (60% capacitance retention at 8 A g^??1). The results of this study suggest the Ni(OH)₂–ECF electrode is an excellent material for fabrication of supercapacitor electrodes.     

<Emphasis Type="Italic">N</Emphasis>-Heterocyclic carbene–copper complex supported on ionic liquid-modified graphene oxide: versatile catalyst for synthesis of (i) 1,2,3-triazole and (ii) propargylamine derivatives

A N-heterocyclic carbene–copper complex grafted on graphene oxide with an ionic liquid framework was prepared. The synthesis of (i) 1,2,3-triazole derivatives by ‘Click reaction’ and (ii) propargylamine derivatives by ‘A³ coupling reaction’ in aqueous media by this new catalyst were all successfully accomplished. The catalyst is characterized using infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, thermogravimetric analysis and energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and elemental analysis. The catalyst is reused in the ten reaction cycles without considerable loss of catalytic activity.

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Effect of solvent on the stability constant of complex formation and the thermodynamic parameters between dicyclohexyl-18-crown-6 with Eu3+, La3+, Er3+ and Y3+ cations

The complexation reaction between Eu³⁺, La³⁺, Er³⁺ and Y³⁺ cations with the dicyclohexyl-18-crown-6 (DCH18C6) in acetonitrile (AN)–dimethylformamide (DMF) and AN–methanol (MeOH) binary systems have been studied at different temperatures using conductometric method. The conductometric data show that the stoichiometry of the complexes is 1:1 [ML]. The results show that the stability constant of complexes in various solvents is: AN > MeOH > DMF. In the some cases, the minimum of logK_f for (DCH18C6–Eu³⁺), (DCH18C6–La³⁺), (DCH18C6–Er³⁺) and (DCH18C6–Y³⁺) complexes in AN–MeOH binary systems obtain at χ_MeOH ~ 0.75, and also, the logK_f of (DCH18C6–Er³⁺) complex in AN–DMF binary systems show a minimum at χ_AN ~ 0.75. Non-linear behavior was observed for the stability constant of complexes versus the composition of the solvent systems. The experimental data show that the selectivity order of DCH18C6 for these cations in AN–MeOH binary systems (mol% AN = 50, 75) at 25 °C is: Y³⁺ > Er³⁺ > Eu³⁺ > La³⁺. The values of thermodynamic parameters (?H?_C) for formation of complexes were obtained from temperature dependence of stability constants of complexes using the van′t Hoff plots and the standard entropy (?S?_C) were calculated from the relationship: ?G?_C, 298.15 = ?H?_C ?298.15?S?_C. The results show that the values of these thermodynamic parameters are influenced by the nature and the composition of the binary systems.