JOURNAL OF THE IRANIAN CHEMICAL SOCIETY(JICS)
Year:2013 | Volume:10 | Issue:4|Papers Count:24

Cloud point extraction (CPE) has been used for the preconcentration and indirect quantification of cyanide after the formation of a ion-associate complex with 3-amino-7-diethylamino-8, 9-benzo-2-phenoxazine chloride (Nile blue, NB+) in the presence of copper (II) ions, and later analysis by flame atomic absorption spectrometry (FAAS) using polyethyleneglycolmono-p-nonylphenylether (PONPE 7.5) as extracting surfactant. The chemical variables affecting the separation phase and the viscosity affecting the detection process were optimized. At pH 5.5, preconcentration of only 50 mL of sample in the presence of 0.04% (w/v) PONPE 7.5 and 5.64×10-5 mol L-1 Nile blue permitted the detection of 3.75 mg L-1 cyanide. The enhancement factor was 64.7 for cyanide. The proposed method was successfully applied to the determination of free cyanide in environmental water samples. The method was compared with the pyridine-barbituric acid method and the paired t test was used to determine whether the results obtained by the two methods differ significantly.

A simple, low-cost and sensitive method is demonstrated for derivatization and extraction of iodine from milk samples using hollow fiber liquid-phase microextraction (HF-LPME) and gas chromatography-electron capture detection. Iodide ions are converted to iodine under acidic medium and in the presence of an oxidant. The generated iodine reacted with 3-pentanone in extraction vial to give 2-iodo-3-pentanone and was extracted into 4 mL of 1-octanol located in the lumen of a hollow fiber. Organic solvent was selected using one variable at a time optimization method and the other main factors affecting derivatization and HF-LPME procedures were evaluated using a Taguchi’s L16 (45) orthogonal array. Under optimal conditions, the method showed low limit of detection (0.5 ng mL-1), wide linear range (1-2,000 ng mL-1) with good correlation coefficient (0.9997) and acceptable relative standard deviation (4.6%, n=5). Finally, the developed method was successfully applied for determination of iodide in real samples including infant milk formulas and cow milk with reasonable relative recoveries (99.8-110.5%).

A new, simple and efficient method for the synthesis of novel isoxazolyl-2-azaspiro [4.5] deca-1, 6, 9-trien-8-ones is described by the intramolecular ipso-cyclization of 5-[(E)-2-(4-methoxyphenyl)-1-ethenyl]-3-methyl-4-nitroisoxazole with nitriles. In presence of 5-[(E)-2-(4-methoxyphenyl)-1-ethenyl]-3-methyl-4-nitroisoxazole, a variety of nitriles underwent the intramolecular ipso-cyclization smoothly, affording title compounds in moderate to good yields.

We use the molecular dynamics-based method to predict the solid-state 13C NMR lineshape of a planar molecule in a nonspherical cage. Unlike linear molecules, three components of the chemical shielding tensor of a planar molecule are different which gives rise to a different lineshape and temperature dependence in the 13C NMR spectrum. We study the planar ethylene molecule in the oblate large cages of the structure I (sI) clathrate hydrate and extract the lineshapes from the angular distribution and dynamics at four temperatures (70, 150, 200, and 250 K) in the stability range of the hydrate. At low temperature, the C2H4 molecules have limited range of motion in the cages, but as the temperature is raised, they first gain greater rotational freedom about the molecular C=C axis, and then in other directions. These data allow for the calculation of the 13C NMR lineshapes of the C2H4 guests at each temperature.

In this study, an ion imprinted polymer (IIP) was prepared for the selective separation and preconcentration of trace levels of aluminum. Al (III) IIP was synthesized in the presence of Al (III)-8-hydroxyquinoline (oxine) complex using styrene and ethylene glycol dimethacrylate as a monomer and crosslinker, respectively. The imprinted Al (III) ions were completely removed by leaching the IIP with HCl (50% v/v) and were characterized by FTIR and scanning electron microscopy. The maximum sorption capacity for Al (III) ions was found to be 3.1 mg g-1 at pH 6.0. Variables affecting the IIP solid phase extraction were optimized by the univariable method. Under the optimized conditions, a sample volume of 400 mL resulted in an enhancement factor of 194. The detection limit (defined as 3 Sb/m) was found to be 1.6 mg L-1. The method was successfully applied to the determination of aluminum in natural water, fruit juice and cow milk samples.

The TfOH/C was readily prepared via simple absorption of triflic acid onto activated charcoal. This solid acid was used as an efficient catalyst for the synthesis of a-aminophosphonates through the Kabachnik-Fields reaction of carbonyl compound, amine and diethyl phosphite under solvent-free conditions.

A density functional theory (DFT) study-based method B3LYP/6-311++G** was carried out to investigate the methyl groups substitution effect on the structure and the strength of intramolecular hydrogen bonding in naphthazarin (NZ) (5, 8-dihydroxy-1, 4-naphthoquinone). The full geometry optimization of molecular structures, the difference between the energies of hydrogen-bonded and non-hydrogen-bonded rotamers, and the proton chemical shift of the hydroxyl groups in NZ and its methyl substituents obtained at the B3LYP/6-311++G** level. The vibrational frequencies of all samples and their deuterated analogues were calculated at the same theoretical level. The 1H chemical shifts for NZ and its methyl substituents were computed at the B3LYP/6-311++G** level using the gauge-including atomic orbital method. Furthermore, in order to investigate the changes in bond order, electron density, electron delocalization, and steric effects caused by methyl substituents, natural bond orbital analysis were carried out at the B3LYP/6-311++G** level. After comparing these effective parameters in methyl substituents with those of their parent, NZ, we concluded that, in general, intramolecular hydrogen bonding strength increases by substituting methyl groups in the different positions of NZ.

The synthesis of nitrogen containing heterocyclic compounds from diethyl ester, formaldehyde, and various aromatic/aliphatic amines via a simple and efficient one-pot multicomponent reaction in ionic liquid is described. The catalyst can be recycled at least three times without obvious loss in catalytic activity.

New hybrid nanostructure-based magnetic drug delivery systems (HNMDDSs) consisting of carbon nanotubes, magnetic iron oxide nanoparticles, and linear-dendritic copolymers linked to anticancer drugs were synthesized and characterized. Polyamidoamine-polyethylene glycol-polyamidoamine (PAMAM-PEG-PAMAM) ABA type linear-dendritic copolymers were used to solubilize and functionalize carbon nanotubes through supramolecular chemistry. There are three key features of HNMDDSs: (a) use of functionalized MWCNTs as a biocompatible platform for the delivery of magnetic iron oxide nanoparticles, therapeutic drugs, and diagnostics, (b) use of PAMAM-PEG-PAMAM linear-dendritic copolymers as water soluble, biocompatible and high functional hybrid materials with a linear polyethylene glycol part which cause a high solubility for MWCNT through supramolecular interactions and dendritic PAMAM parts which cause a high functionality for MWCNT, (c) use of magnetic iron oxide nanoparticles as targeting, imaging, or hyperthermia cancer treatment agents. To prove the efficacy of synthesized HNMDDSs, they were subjected to the receptor-mediated endocytosis and release inside the cancer cells. Then, it was unambiguously proved that these tumor-targeting HNMDDSs are promising systems for future cancer therapy with low drug doses, thereby forming a solid foundation for further investigation and development.

Two new novel ferrocenylaclyhydrazone-based receptors FcL1 and FcL2 were prepared and characterized by 1H NMR, IR, elemental analysis. X-ray crystallographic reveals that FcL1 belongs to Monoclinic system, with space group P2 (1)/c, and FcL2 belongs to Hexagonal system with space group P6 (5). It forms a novel helical chain by self-assembly. The electrochemical studies reveal that the formal potential (E0) of FcL1 and FcL2 show a gradual decrease in the order Fc (Ferrocene) < FcL1<FcL2 and FcL1 is responsive to Pb2+. The maximum electrochemical shift of FcL1 for Pb2+ is about 44 mV. FcL1 shows selective potential response to Pb (II) ion.

A new and highly efficient method for the C-N bond formation using molecular iodine-catalyzed N-alkylation reaction of tosylhydrazones with benzylic/benzhydryl alcohols at room temperature in methylene chloride is described. A variety of tosylhydrazones reacted readily with various substituted benzylic alcohols in presence of 20 mol % iodine under mild reaction conditions to produce the corresponding biologically active N-alkylated compounds in good to excellent yields.

The one-pot three-component reaction of primary and secondary amines, carbon disulfide and b-nitrostyrene derivatives in neat condition at room temperature afforded functionalized dithiocarbamate derivatives in good to high yields. High bond-forming efficiency and easy work-up are advantages of this reaction. In vitro antimicrobial activities of synthesized compounds were studied against four Gram-positive bacteria, four Gram-negative bacteria and four fungi. The screening for the antimicrobial activity was performed by twofold serial dilution technique. Notably, some synthesized compounds displayed comparable or even better antibacterial and antifungal activities against some tested strains than the reference drugs ampicillin, streptomycin and amphotericin B, respectively.

To deepen the understanding the interactions of thiophenic compounds in ionic liquids, we have performed a systemic study on the electronic structures, and topological properties of interactions between N-ethyl-N-ethylimidazolium diethyl phosphate ([EEIM] [DEP]) ionic liquid and 3-methylthiophene (3-MT), benzothiophene (BT), or dibenzothiophene (DBT) using density functional theory. From NBO atomic charges and electrostatic potential analyses, most of the positive charge is located on C2-H2 in the [EEIM] cation, and the negative charge is focused on oxygen atoms in [DEP] anion, implying oxygen atoms in [DEP] should easily attack C2-H2 in [EEIM]. The electrostatic interaction between anion and cation may be dominant for the formation of the [EEIM]-[DEP] ion pair. The large stabilizing effect is due to the strong orbital interactions between the antibonding orbital of proton donor s*(C2-H2) in [EEIM] cation and the lone pairs of proton acceptor LP (O) in [DEP] anion. A common feature of [EEIM] [DEP], [EEIM] [DEP]-3-MT/BT/DBT complexes is the presence of hydrogen bonds between [EEIM] cation and [DEP] anion. This work has also given the interacting mechanism of 3-MT, BT, and DBT adsorption on [EEIM] [DEP] ionic liquid. Both [EEIM] cation and [DEP] anion are shown to play important roles in interactions between 3-MT, BT, DBT and [EEIM] [DEP], which has been corroborated by NBO and AIM analyses. The p···p, p···C-H and hydrogen bonding interactions occur between [EEIM] [DEP] and 3-MT, BT, DBT. The strength of sulfur involved interactions between 3-MT, BT, DBT and [EEIM] [DEP] follows the order of 3-MT>BT>DBT. The order of interaction energies between [EEIM] [DEP] and 3-MT, BT, DBT is 3-MT<BT<DBT, in agreement with the order of extractive selectivity from fuel oils (DBT>BT>3-MT) in terms of sulfur partition coefficients.

In the present work, the preparation of 1-amidoalkyl-2-naphthols via one-pot three-component condensation of amides, aldehydes, and b-naphthol in the presence of catalytic amounts of zirconyl triflate, as a highly efficient, low toxic, stable and non-hygroscopic catalyst under solvent-free conditions is reported. This low-cost procedure offers several other advantages such as short reaction times and good to excellent yields.

[Fe(Me-phen)Cl4][Me-phen H] (1) and [Fe(Cl-phen)Cl4][Cl-phen H] (2) complexes were prepared from the reactions of FeCl3 6H2O with 5-methyl-1, 10-phenanthroline (Me-phen) and 5-chloro-1, 10-phenanthroline (Cl-phen), respectively, in a 0.1 M aqueous solution of HCl. Stepwise addition of dimethyl sulfoxide to the solution of 1 in methanol results in a mixed ligand complex, [Fe(Me-phen)Cl3(DMSO)] (3). Complex 3 was also prepared by two other methods. The reaction of a methanol solution of [Fe(Me-phen)Cl4][Me-phen H] (1) with [Fe(DMSO)4Cl2][FeCl4] in 1:6 ratio led to3. Complex 3 was also prepared from the reaction of 5-methyl-1, 10-phenanthroline with [Fe(DMSO)4Cl2][FeCl4] in 1:1 ratio in methanol. The three complexes were characterized by IR, UV-Vis, 1H NMR and luminescence spectroscopy and their structures were studied by the single-crystal diffraction method. Calculation methods were employed to study the isomerization of (3) in solution.

Five novel aminomethylphosphinic acid ligands (L1-L5) have been synthesized and characterized. The pH-potentiometric technique was used for determining the dissociation constants (pK) of the compounds. The stabilizing ability of complexes of a novel chiral ligand of bis (aminomethyl) phosphinic acid (L1) with transition metals such as Co2+, Ni2+, Zn2+, Fe2+, Cu2+, Cd2+ and lanthanide ions La3+, Gd3+ in aqueous solutions have been studied by the pH-potentiometric technique. The complexation studies show that there is a significant difference between transition metals and lanthanide ions.

Cadmium oxide (CdO) nanoplatelets were synthesized by thermal decomposition of cadmium malonate. The synthesized CdO nanoplatelets were characterized by X-ray diffraction (XRD); from the XRD analysis, it is clear that the phase structure of CdO nanoplatelets was found to be face-centered cubic with the average crystalline size of 40-50 nm. FT-IR analysis shows the presence of surface carboxyl and hydroxyl groups on to the CdO nanoplatelets. From DRS-UV-Vis analysis, both the direct and indirect band gaps of the CdO nanoplatelets were found to be 2.0 and 1.67 eV, respectively. From the FE-SEM analysis, the morphology of the synthesized CdO was found to be nanoplatelets, which were randomly agglomerated. Further, HR-TEM was used to confirm the formation of nanoplatelets. The electrochemical sensing property of CdO nanoplatelets was carried out by cyclic voltammetry (CV) by coating CdO nanoplatelets on Glassy carbon electrode (GCE) and using it as working electrode for sensing of catechol. The enhanced electrochemical behaviour is mainly attributed to the nanometer dimensions and surface hydroxyl groups on the CdO nanoplatelets. Chronoamperometry (CA) was used to determine the sensitivity and repeatability of the modified electrode. The modified electrode shows linear range of catechol concentration between 7.5×10-6 and 1.5×10-4 M with sensitivity of 9.8 nA mM-1.

The catalytic activity of [bmim]5[PW11ZnO39] 3H2O as a hybrid catalyst was studied in the oxidation of various alkenes in acetonitrile, using hydrogen peroxide as oxygen source. The effect of reaction parameters such as type of solvent and oxidant, amount of catalyst and oxidant, and temperature was also investigated. From our results, [bmim]5[PW11ZnO39] 3H2O hybrid catalyst gave higher yields and selectivity in the oxidation of alkenes and was reused four times without loss of its catalytic activity.

Here, we describe the chemiresistive sensing of some volatile organic compounds with a novel film of chemically synthesized Au-Pt bimetallic nanoparticles (NPs) stabilized with 11-mercaptoundecanoic acid. The chemiresistive sensing properties were measured over a concentration range of 1.4-250 mg L-1 for methanol, ethanol, ethyl acetate and acetone vapours and the responses were compared with Au and Pt monometallic nanoparticles. It is observed that the sensitivity of bimetallic nanoparticles is increased about 60% in exposure to methanol and ethanol vapours, but there are no changes in the sensitivity to the other tested vapours. In addition, the detection limit is improved about 80-100% for all tested vapours in bimetallic nanoparticles compared to AuNPs and 20-30% compared to PtNPs.

In current study, quaternized highly branched polyacrylamide (HBAA) was synthesized and used as an efficient multi-site polymeric phase transfer catalyst in nucleophilic substitution reactions and also in synthesis of a, b-unsaturated nitriles from reaction of acetonitrile and carbonyl compounds. The quaternized HBAA was synthesized via two steps. First, HBAA was synthesized via self-condensing vinyl polymerization of acrylamide at appropriate molar ratio of monomer to diperiodatocuprate (III). In the second step, 3-acrylamidopropyl trimethylammonium iodide was polymerized on peripheral area of the HBAA in the presence of diperiodatocuprate (III) solution again. The thermal behavior of HBAA and that of the quaternized HBAA were studied by DSC and TGA analysis. This phase transfer catalyst was easily recovered after reaction and reused several times without any loss of activity.

Concentration effect of silver nanoparticles (AgNPs) on the photophysical properties of ciprofloxacin (Cip) have been investigated using optical absorption and fluorescence techniques. When performed AgNPs solution was added to the Cip solution, metal-enhanced fluorescence intensity and a blue-shift of 20 nm in the maximum emission spectra of Cip has been observed. The enhanced intensity of this system is strongly dependent on the AgNPs concentration and largest at the 6.0´10-6 mol L-1. With increase of AgNPs concentration, quenching of fluorescence is observed. Stern-Volmer quenching constants have been calculated at four temperatures. The results show the quenching constants are directly correlated with temperature. It indicates the quenching mechanism is the dynamic quenching in nature rather than static quenching. From which we determined the activation energy for the quenching of Cip-AgNPs to be about 31.1 kJ mol-1. In addition, in the presence of optimum AgNPs concentration, a sensitive fluorimetric method for the determination of ciprofloxacin at the range 5.0´10-7-3.0´10-5 mol L-1 and the detection limit of 2´10-8 mol L-1 in solution is proposed.

The synthesis of six new symmetrical disazo direct dyes containing 4,4’-diaminostilbene-2,2’-disulphonic acid as middle component and N-(2-chlorophenyl)-2-hydroxybenzamide, N-(3-chlorophenyl)-2-hydroxybenzamide, N-(4-chlorophenyl)-2-hydroxybenzamide, N-(2-bromophenyl)-2-hydroxybenzamide, N-(3-bromophenyl)-2-hydroxybenzamide, N-(4-bromophenyl)-2-hydroxybenzamide as coupling components is presented. The synthesized dyes were analyzed by thin layer chromatography, electronic spectra and HPLC technique. Their structures were elucidated by FT/IR and 13C-NMR spectroscopy. The CIELAB (1976) colour space was used in all the colour measurements for the six disazo stilbene dyes under the CIE recommended illuminants: D65 (natural day light), A (tungsten light), F2 (fluorescent light) and the standard 10° observer, respectively. The colour differences: DEab* and DECMC were calculated against one standard. The results reveal a good colouring power of the new azo-stilbene dyes.

In this study, the solution chemistry and solid-state structures of a novel proton transfer compound, (pipzH2) (pyc)2·H2O 1, and three metal-organic complexes of [Mn (pyc)2(H2O)2]2·2H2O 2, [Ni(pyc)2(H2O)2]·H2O 3 and [Cu(pyc)2H2O]n 4, (pyc=pyridine-2-carboxylate, pipz=piperazine) were investigated. On the basis of crystallographic data, each MII ion is coordinated to pyridine-2-carboxylate as bidentate ligand. Furthermore, these complexes form a three-dimensional structure by a variety of noncovalent interactions such as extensive O-H···O, O-H···N, N-H···O, N-H···N, C-H···O hydrogen bonds, C-H···p and C-O···p interactions. The equilibrium constants for the binary pyc-pipz proton transfer system, the stoichiometry and stability of complexation of this system with Mn2+, Ni2+ and Cu2+ ions in aqueous solution were investigated by potentiometric pH titration method. In each case, the stoichiometry of the dominant metal complex species in solution was compared with that obtained from the crystal structure.

In this study, the inhibitive effect of synthesized 1-(7-methyl-5-morpholin-4-yl-thiazolo [4, 5-d] pyrimidin-2-yl)-hydrazine (MMTPH) as a new corrosion inhibitor for mild steel in 0.5 M sulfuric acid medium is investigated employing potentiodynamic polarization, electrochemical impedance spectroscopy and linear polarization resistance techniques. The results show MMTPH reduces anodic dissolution, retards the hydrogen evolution reaction and its adsorption follows Langmuir’s adsorption isotherm. Any increase in temperature will in turn increase corrosion current densities; however, the presence of MMTPH hinders the rate. In solutions with inhibitor concentration of 200 ppm, temperature elevations as great as 30o (25-55oC) result in a drop of about 45% in inhibition efficiency (99-55%). Thermodynamic adsorption parameters show that the MMTPH is absorbed by a spontaneous exothermic process and the adsorption mechanism is physical. Quantum chemical method shows that the MMTPH molecules can be directly adsorbed at the steel surface on the basis of donor-acceptor interactions between p-electrons of pyrimidine, N atoms of hydrazine and vacant d-orbitals of iron atoms.