نشریه شیمی کاربردی روز
پیاپی 37 (زمستان 1394)

Oxovanadium(IV) Schiff base complex of N,N′-bis(5- [(triphenylphosphoniumchloride)-methyl-salicylidinenaphthal-diamine)] was synthesized, characterized and immobilized on sodium montmorillonite as a heterogeneous catalyst. The net Schiff base complex and supported complex were characterized by X-ray diffraction spectroscopy, IR spectroscopy, diffuse reflectance spectroscopy and atomic absorption spectroscopy techniques. The diffuse reflectance spectra data and IR spectra of the supported Schiff base complex show that the complex was physically entrapped within sodium montmorillonite. The novel heterogeneous catalyst shows excellent catalytic activity in epoxidation of olefins using tert-butylhydroperoxide in acetonitrile. In this report, the supported vanadyl complex exhibited 100% selectivity for epoxidation with 91% and 90% conversion for cyclohexene and cyclooctene, respectively. The supported oxovanadium(IV) complex gave higher percent of conversion of olefins than neat oxovanadium(IV) Schiff base complex.

In recent years, the use of natural antioxidants extracted from agricultural and industrial by-products has been increased because of sustainability, high and stable antioxidant activity, absence of toxicity. These extracts can be used as substitute of synthetic antioxidants for food products, color and oxidative stabilization. In this study, experimental design and response surface methodology (RSM) were used to optimize experimental variables such as sample weight (g), irradiation power and time (s) in microwave-assisted extraction (MAE) of antioxidants from pistachio hull. Effect of sample weight was found to be significant on total phenolic content (TPC), ferric reducing antioxidant power (FRAP), scavenging activity of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and extraction yields. The optimal conditions were water as solvent, particle size of 0.25 mm, microwave power 600 W, sample weight 0.2 g, irradiation time of 150 s. Finally, comparison of extraction methods was shown that MAE method gave better results than ultrasonic-assisted extraction (UAE) and conventional methods with the optimum operating conditions like time and energy consumption.

The main purpose of the present study is to synthesis different fullerene (C60)-based metal (Ni, Pd, Pt, Ru and Rh) nanocatalysts that is used for the catalytic hydrogenation of benzene in gasoline. Metal catalysts were then loaded with the impregnation method and deposited on the functionalized fullerene. Response surface methodology (RSM) was used to investigate the cumulative effect of various parameters including pressure, temperature, time and loading and to optimize these parameters to maximizing the hydrogenation of benzene in gasoline. The catalysts were characterized before reaction by XRD, TEM and TGA. The results show that the yield of hydrogenation under optimum conditions (include metal loading of about 10%, reaction time of 180 min and hydrogen pressure of 50 atm) are obtained: 99.59, 99.48, 98.09, 98.51 and 97.56%, for Rh, Ru, Pt, Pd and Ni, respectively. These results are obtained by the diffrent reaction time for Rh, Ru, Pt, Pd and Ni following: 180, 125, 31.25, 180 and 180 min respectively.

The direct polycondensation reactions of diacid, 5-(3-acetoxynaphthoylamino)isophthalic acid with various aromatic and aliphatic diisocyanates such as 4,4'-methylene bis(4-phenylisocyanate), toluylene-2,4-diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate were carried out under microwave irradiation conditions. In order to compare this method with classical heating, the polymerization reactions were also performed under solution polycondensation conditions. The polymerization reactions occurred rapidly under microwave conditions and produced a series of polyamides containing pendent acetoxynaphthalamide group, with good yields and moderate inherent viscosities of 0.26-0.45 dL/g. The comparable yields and higher inherent viscosities were obtained by microwave irradiation versus thermal heating with substantial reduction in reaction time.

A simple, practical and convenient procedure for the synthesis of quinoxaline derivatives has been developed by reaction of 1,2-phenylenediamines with 1,2-diketones in the presence of sodium dodecyl sulfate (SDS) in the aqueous medium at room temperature without any organic solvent.

Bronsted acidic ionic liquid, [Et3N–SO3H]Cl, catalyzed the reaction of acetic anhydride with aryl aldehydes under solvent-free condition. Various 1,1-diacetates are obtained using 15 mol% of triethylamine-bonded sulfonic acid in satisfactory to excellent yields in very short reaction times at ambient temperature. Different groups including electron donating or electron withdrawing groups linked to benzene ring such as methyl, chloro, nitro and methoxy were tolerated under the optimized reaction conditions. This ionic liquid was air stable and easily prepared from accessible amine and chlorosulfonic acid. The present report is a green protocol as it eliminates the need of an organic solvent. Very short reaction times, high yields, simple operational procedure and green conditions are merits of this methodology.

Hydrogen storage capacity of defected graphene was studied by first-principles theory based on Density-functional calculations. Adsorption of molecular hydrogen on a defected graphene V2(5-8-5) and lithium doped defected graphene V2(5-8-5) was carried out. Hydrogen molecules are physisorbed on defected graphene V2(5-8-5) with binding energy about 21–48 meV. Whereas the binding energies increase up to 150–152 meV in Li doped defected graphene. Charge-density analysis indicated that the increasing of binding energy is due to the charge transfer from the H2 molecule to Li . The results explain the enhancement of storage capacity observed in some experimental hydrogen adsorption on defected graphene qualitatively.

A new uranyl Schiff base complex, [UO2(L)(DMF)] where L= 2, 2'-((1E, 1E')-(1, 2 phenylen bis (azanylylidene)) bis (methanylylidene)) bis (4-bromo phenol) by reaction between of H2L and (CH3COO)2UO2·2H2O was successfully synthesized. The complex characterized by FT-IR, 1H NMR as well as electronic and luminescence property measurements. This complex was used as a novel precursor for preparing U3O8 nanopowder at low temperature (400 ˚C) by decomposition method. The average crystallite size of the U3O8 nanopowder that has been synthesized is about 22. nm as determined by the Scherrer equation. According the results, we found that U3O8 could stop biofilm formation in S. aureus PTCC 1112 (0.632 mg/ml), M. luteus PTCC 1110 (0.633 mg/ml) and E. faecalis (0.633 mg/ml). Also, U3O8 repressed biofilm formation in M. luteus PTCC 1110 (0.625 mg/ml), E. faecalis (0.313 mg/ml) and C. albicans PTCC 5027 bacterias (1.27 mg/ml).

An efficient and environmental friendly methodology for the synthesis of polysubstituted dihydro-2-oxypyrroles via a one-pot four-component domino condensation of dialkyl acetylenedicarboxylate, formaldehyde and amines (aromatic and aliphatic) at present of salicylic acid as an economical and naturally green Brønsted acid catalyst under ambient temperature with excellent yields and short reaction times is described. Green, natural, inexpensive and non-toxic catalyst, easily separated with no column chromatographic separation and highly efficient is an option for the simple synthesis of these rings.