New One‐Pot Procedure for the Synthesis of 2‐Substituted Benzimidazoles

A highly selective synthesis of 2‐substituted benzimidazole derivatives from the reaction of o‐phenylendiamine derivatives and aromatic aldehydes in the presence of an organic salt, NH₄OAc, in absolute ethanol is presented. The products were obtained by evaporating the solvent followed by a simple recrystallization with excellent yields.     

Knoevenagel‐Michael‐cyclocondensation Tandem Reaction of Malononitrile,Various Aldehydes and Dimedone Catalyzed by Sulfonic Acid Functionalized Pyridinium Chloride as a New Ionic Liquid and Catalyst

New ionic liquid sulfonic acid functionalized pyridinium chloride [Pyridine–SO₃H]Cl was used for the synthesis of tetrahydrobenzo[b]pyran derivatives by the one‐pot three component condensation reaction of various aldehydes, dimedone and malononitrile at 95 ºC under solvent‐free conditions.     

Thermal conductivity of Al2O3/water nanofluids

A considerable number of studies can be found on the thermal conductivity of nanofluids in which Al₂O₃ nanoparticles are used as additives. In the present study, the aim is to measure the thermal conductivity of very narrow Al₂O₃ nanoparticles with the size of 5 nm suspended in water. The thermal conductivity of nanofluids with concentrations up to 5 % is measured in a temperature range between 26 and 55 °C. Using the experimental data, a correlation is presented as a function of the temperature and volume fraction of nanoparticles. Finally, a sensitivity analysis is performed to assess the sensitivity of thermal conductivity of nanofluids to increase the particle loading at different temperatures. The sensitivity analysis reveals that at a given concentration, the sensitivity of thermal conductivity to particle loading increases when the temperature increases.     

Enhancing Multicomponent Metal–Organic Frameworks for Low Pressure Liquid Organic Hydrogen Carrier Separations

The resurgence of interest in the hydrogen economy could hinge on the distribution of hydrogen in a safe and efficient manner. Whilst great progress has been made with cryogenic hydrogen storage or liquefied ammonia, liquid organic hydrogen carriers (LOHCs) remain attractive due to their lack of need for cryogenic temperatures or high pressures, most commonly a cycle between methylcyclohexane and toluene. Oxidation of methylcyclohexane to release hydrogen will be more efficient if the equilibrium limitations can be removed by separating the mixture. This report describes a family of six ternary and quaternary multicomponent metal–organic frameworks (MOFs) that contain the three-dimensional cubane-1,4-dicarboxylate (cdc) ligand. Of these MOFs, the most promising is a quaternary MOF (CUB-30), comprising cdc, 4,4′-biphenyldicarboxylate (bpdc) and tritopic truxene linkers. Contrary to conventional wisdom that adsorptive interactions with larger, hydrocarbon guests are dominated by π–π interactions, here we report that contoured aliphatic pore environments can exhibit high selectivity and capacity for LOHC separations at low pressures. This is the first time, to the best of our knowledge, where selective adsorption for cyclohexane over benzene is witnessed, underlining the unique adsorptive behavior afforded by the unconventional cubane moiety.     

Sulfur-nanoparticle-based method for separation and preconcentration of some heavy metals in marine samples prior to flame atomic absorption spectrometry determination

The application of sulfur-nanoparticle-loaded alumina as an efficient adsorbent for the solid-phase extraction (SPE) and determination of trace amounts of Cd, Cu, Zn, and Pb ions was investigated in marine samples using flame atomic absorption spectrometry (FAAS). The nanometer-sized sulfur particles were synthesized in situ, physically loaded onto alumina microparticles, and the parameters influencing the preconcentration of the analytes, such as the pH, solution flow rate and volume, eluent solution, and interfering ions, were examined. The results showed that the optimal conditions for quantitative recovery of the metal ions by adsorption and elution on the sulfur nanoparticles (SNPs) was achieved by employing a flow rate of 15 mL min(-1), a pH of 8.5 for the sample solutions, and an eluent composed of 3.0 mol L(-1) HNO(3) in methanol. The detection limits of this method for Cd, Zn, Cu, and Pb ions were 0.30, 0.21, 0.24, and 0.63 μg L(-1) (n=10), respectively. Application of the proposed method to the analysis of fish certified reference material (DORM-3) produced results that were in good agreement with the certified values. The proposed method was also successfully applied to the determination of analytes in marine samples, including seawater, fish, and oysters.     

Coordination polymers based on building blocks of dimethyltin(IV) Chloride iso‐thiocyanate and dimethyltin(IV) di‐iso‐thiocyanate with pyrazine‐2‐carboxylate and 4, 4′‐bipyridine

The reaction of 4,4′‐bipy with dimethyltin(IV) chloride iso‐thiocyanate affords the one‐dimensional (1D) coordination polymer, [Me₂Sn(NCS)Cl·(4,4′‐bipy)]_n ( 1 ), whereas reaction of dimethyltin(IV) dichloride with sodium pyrazine‐2‐carboxylate in the presence of potassium iso‐thiocyanate affords the two‐dimensional (2D) coordination polymer, {[Me₂Sn(C₄H₃N₂COO)₂]₂ [Me₂Sn(NCS)₂]}_n ( 2 ). Both coordination polymers were characterized by elemental analysis and infrared spectroscopy in addition to ¹H and ¹³C NMR spectroscopy of the soluble coordination polymer ( 1 ). A single‐crystal structure determination showed that the asymmetric unit in 1 contains Me₂Sn(NCS)Cl and 4,4′‐bipy moieties and a 1D infinite rigid chain structure forms through bridging of the 4,4′‐bipy ligand between tin atoms and the geometry around the tin atom is a distorted octahedral. Coordination polymer 2 contains two distinct tin atom geometrics in which one tin atom is seven coordinate, and the other is six coordinate. The two tin atom environments are best described as a pentagonal bipyramidal in the former and distorted octahedral in the latter where the carboxylate groups bridge the two tin atoms and construct a 2D‐coordination polymer. The ¹¹⁹Sn NMR spectroscopy indicates the octahedral geometry of 1 retains in solution. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:699–706, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/.20736     

Dipyridylamine-modified nanoporous silicas as new sorbents for the separation and pre-concentration of palladium

Nanoporous silicas of the type SBA-15 (Santa Barbara Amorphous) and MCM-48 (Mobile Composition of Material) were modified with dipyridylamine (dipy) and used as solid phases for the extraction of Pd(II) ions. The experimental conditions (pH, sample and eluent flow rates, type and quantity of eluent) were optimized. The recovery values were ~ 99.7 and ~ 93.4% for dipy-MCM-48 and dipy-SBA-15, respectively, the limits of detection were <0.08 and <0.11 ng L^?1, the pre-concentration factors were 725 and 550, and the adsorption capacity was >78 mg g^?1. The procedure was applied to the preconcentration of Pd(II) in real samples.

Micro‐arc oxidation and electrophoretic deposition of nano‐grain merwinite (Ca3MgSi2O8) surface coating on magnesium alloy as biodegradable metallic implant

Magnesium alloys are promising biomaterials as biodegradable implant for orthopedic applications. However, their low corrosion resistance and poor bioactivity have prohibited their implant applications. In order to enhance these two properties, a nano‐grain merwinite coating was prepared on magnesium alloy. Its corrosion and the bioactivity behavior were characterized with electrochemical and immersion tests. The results showed that the nano‐grain merwinite coating can improve both the corrosion resistance and the bioactivity of the magnesium alloy making it an appropriate material for biodegradable bone implants. Copyright © 2014 John Wiley & Sons, Ltd.     

Application of molecularly imprinted polymer for solid phase extraction and preconcentration of Hydrochlorothiazide in pharmaceutical and serum sample analysis

A new polymeric sorbent prepared by utilizing molecular imprinting technology was used for the selective extraction of hydrochlorothiazide (HCT) from pharmaceutical and human serum sample. The molecularly imprinted polymer (MIP) was prepared using HCT as the template, methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate (EDMA) as the cross-linker monomer, and dimethylformamide (DMF) as a solvent. The optimized conditions of MIPs as a selective sorbent for the preconcentration of the HCT were studied. The results showed that the drug could be quantitatively and selectively maintained in the column to be then eluted from the sorbent by using methanol-acetic acid mixture (9:1). HCT could be determined spectrophotometrically at λ_max = 270 nm. This method made it possible to quantitize HCT in the range of 0.1–21.0 μg ml^-1, by less than 0.55% of RSD%, with a detection limit (S/N = 3) of 0.073 ng ml^-1. The preconcentration factor of 1000, recoveries of up to 96% and retention capacity of 75.0 mg g_-1 were achieved using this technique.