Synthesis and characterization of three new organotin complexes containing piperazine as a bidentate ligand

The reaction of dichlorostannanes R₂SnCl₂ (R=Me 1, Buⁿ 2) with piperazine ligand in molar ratio 1:2, in dry methylene dichloride, in an inert atmosphere leads to the synthesis of R₂Sn(C₄H₉N₂)₂(R=Me 1, Buⁿ 2). In a similar manner, The reaction between Ph₂SnCl₂ and piperazine in dry ethanol in molar ratio 1:1 produces [Ph₂Sn(C₄H₈N₂)]₂ (3). The yields of these new products were excellent and they have been fully characterized by FT-IR, UV–Vis, multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR spectroscopy and mass spectrometry, as well as elemental analysis. The spectroscopic results indicate that the piperazine ligand is coordinated to tin atom of organotin moieties, through the nitrogen atoms. Furthermore, the ligand behaves as a bidentate fashion in (1) and (2) and gives 1:2 substitution products, while in the complex (3) the two six-membered rings bind in bidentate-chelate forms between the two Sn atoms.     

SMFs-supported Pd nanocatalysts in selective acetylene hydrogenation: Pore structure-dependent deactivation mechanism

In the present study, CNFs, ZnO and Al₂O₃ were deposited on the SMFs panels to investigate the deactivation mechanism of Pd-based catalysts in selective acetylene hydrogenation reaction. The examined supports were characterized by SEM, NH₃-TPD and N₂ adsorption-desorption isotherms to indicate their intrinsic characteristics. Furthermore, in order to understand the mechanism of deactivation, the resulted green oil was characterized using FTIR and SIM DIS. FTIR results confirmed the presence of more unsaturated constituents and then, more branched hydrocarbons formed upon the reaction over alumina-supported catalyst in comparison with the ones supported on CNFs and ZnO, which in turn, could block the pores mouths. Besides the limited hydrogen transfer, N₂ adsorption-desorption isotherms results supported that the lowest pore diameters of Al₂O₃/SMFs close to the surface led to fast deactivation, compared with the other catalysts, especially at higher temperatures.     

Carbon/carbon supercapacitors

Supercapacitors, or electrochemical capacitors, are a power storage system applied for harvesting energy and delivering pulses during short periods of time. The commercially available technology is based on charging an electrical double-layer (EDL), and using high surface area carbon electrodes in an organic electrolyte. This review first presents the state-of-the-art on EDL capacitors, with the objective to better understand their operating principles and to improve their performance. In particular, it is shown that capacitance might be enhanced for carbons having subnanometric pores where ions of the electrolyte are distorted and partly desolvated. Then, strategies for using environment friendly aqueous electrolytes are presented. In this case, the capacitance can be enhanced through pseudo-faradaic contributions involving i) surface functional groups on carbons, ii) hydrogen electrosorption, and iii) redox reactions at the electrode/electrolyte interface. The most promising system is based on the use of aqueous alkali sulfate as electrolyte allowing voltages as high as 2 V to be reached, due to the high overpotential for di-hydrogen evolution at the negative electrode.     

Fabrication and application of a new modified electrochemical sensor using nano-silica and a newly synthesized Schiff base for simultaneous determination of Cd,Cu and Hg ions in water and some foodstuff samples

A new chemically modified carbon paste electrode was constructed and used for rapid, simple, accurate, selective and highly sensitive simultaneous determination of cadmium, copper and mercury using square wave anodic stripping voltammetry (SWASV). The carbon paste electrode was modified by N,N′-bis(3-(2-thenylidenimino)propyl)piperazine coated silica nanoparticles. Compared with carbon paste electrode, the stripping peak currents had a significant increase at the modified electrode. Under the optimized conditions (deposition potential, −1.100 V vs. Ag/AgCl; deposition time, 60 s; resting time, 10 s; SW frequency, 25 Hz; pulse amplitude, 0.15 V; dc voltage step height, 4.4 mV), the detection limit was 0.3, 0.1 and 0.05 ng mL⁻¹ for the determination of Cd²⁺, Cu²⁺ and Hg²⁺, respectively. The complexation reaction of the ligand with several metal cations in methanol was studied and the stability constants of the complexes were obtained. The effects of different cations and anions on the simultaneous determination of metal ions were studied and it was found that the electrode is highly selective for the simultaneous determination of Cd²⁺, Cu²⁺ and Hg²⁺. Furthermore, the present method was applied to the determination of Cd²⁺, Cu²⁺ and Hg²⁺ in water and some foodstuff samples.     

Evaluation of Antimicrobial Activity of Some Newly Synthesized 4‐Thiazolidinones

The antimicrobial activity of thirteen newly synthesized 4‐thiazolidinones (TZONs) and four dithiolane derivatives was assessed against susceptible and resistant bacteria, including MRSA, as well as Candida albicans. The structure‐activity relationships revealed that 4‐Thiazolidinone derivatives harboring p‐chlorophenyl and dicarboxyethyl at the 2‐ethenyl and 5‐arylidine positions of the thiazolidinone ring display considerable antibacterial properties. No antifungal activity was recorded by all tested compounds against Candida albicans. The possible potentiative (synergistic) effect of the most active compounds to a few commercial antibiotics was also investigated.     

Evaluation of Antifungal and Antioxidant Activity of Newly Synthesized 4‐Thiazolidinones

The antifungal and antioxidant activities of thirty newly synthesized 4‐thiazolidinone (TZON) derivatives were assessed against some fungal species including Candida albicans and Aspergillus niger. The introduction of different arylidene moieties at 5‐positions of the thiazolidinone ring successfully enhanced its biological activity. The structure–activity relationships revealed that 4‐thiazolidinone derivatives harboring dicarboxyethyl (at the 2‐ethenyl) and p‐nitrophenylhydrazyl arm (at the 5‐arylidine positions of the thiazolidinone ring) display considerable antifungal and antioxidant properties.     

High‐Efficiency Conversion of Trimethylsilyl Ethers to Their Corresponding Ethers using Carbon‐Based Solid Acid as a New Catalyst in Heterogeneous Mixtures

Carbon‐based solid acid was used as a new catalyst for conversion of trimethylsilyl ethers to their corresponding ethers in heterogeneous mixtures. The experiments were done moderately at room temperature, and high yields in suitable times were obtained under these conditions.     

Magnetic solid-phase extraction using Schiff base ligand supported on magnetic nanoparticles as sorbent combined with dispersive liquid-liquid microextraction for the extraction of phenols from water samples

ABSTRACT

In this work, the magnetic sorbent was developed by covalent binding of a Schiff base ligand, N,N’-bis(3-salicyliden aminopropyl)amine (salpr), on the surface of silica coated magnetic nanoparticles (Salpr@SCMNPs). The core-shell nanoparticle was applied for the magnetic solid-phase extraction (MSPE) combined with dispersive liquid-liquid microextraction (DLLME) of phenolic compounds from water samples prior to gas chromatography-flame ionisation detector (GC?FID). Characterisation of the Salpr@SCMNPs was performed with different physicochemical methods such as Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). Variables affecting the performance of both extraction steps such as pH of the water sample, the sorbent amount, the desorption conditions, the extraction time; and extraction solvent were studied. Under the optimised conditions, the analytical performances were determined with a linear range of 0.01–100 ng mL^?1 and a limit of detection at 0.003–0.02 ng mL^?1 for all of the analytes studied. The intra-day (n = 5) and inter-day (n = 3) relative standard deviations (RSD%) of three replicates were each demonstrated in the range of 6.9–8.9% and 7.3–10.1%, respectively. The proposed method was executed for the analysis of real water samples, whereby recoveries in the range of 92.9–99.0% and RSD% lower than 6.1% were attained.     

One-pot synthesis of 1,2,4,5-tetrahydro-2,4-dioxobenzo[b][1,4]diazepine and malonamide derivatives using multi-component reactions

In this work, a new series of 1,2,4,5-tetrahydro-2,4-dioxobenzo[b][1,4]diazepine and malonamide derivatives have been synthesized using an aromatic 1,2-diamine, Meldrum's acid, an isocyanide, and an arylidene malononitrile (or an aldehyde and malononitrile instead of an arylidene malononitrile) in CH₂Cl₂ at ambient temperature. Synthesis of 1,2,4,5-tetrahydro-2,4-dioxobenzo[b][1,4]diazepine proceeded via four- and five-component reactions; while the synthesis of malonamide derivatives was performed using five- and six-component reactions. In addition, a new series of the malonamide derivatives have been prepared using an aldehyde, malononitrile, Meldrum's acid, an isocyanide, and two molecules of 1,4-diamine via a six-component reaction. These procedures provide alternative methods to the synthesis of a new series of 1,2,4,5-tetrahydro-2,4-dioxobenzo[b][1,4]diazepine and malonamide derivatives.