JOURNAL OF THE IRANIAN CHEMICAL SOCIETY(JICS)
Year:2010 | Volume:7 | Issue:4|Papers Count:29

The effects of 2, 2'- [bis-N (4-cholorobenzaldimin)] -1, 1'-dithio (BCBD) and bis- (2-aminophenyl) disulphide (BAPD) on the corrosion behavior of 302 stainless steel in 0.5 M sulfuric acid solution as corrosive medium were investigated using weight loss and potentiostatic polarization techniques. Some corrosion parameters such as anodic and cathodic Tafel slopes, corrosion potential, corrosion current density, surface coverage degrees and inhibition efficiencies were calculated. The polarization measurements indicated that the inhibitors were of mixed type which inhibited corrosion by parallel adsorption on the surface of stainless steel due to the presence of more than one active centre in the inhibitor molecule. The adsorption followed Langmuir adsorption isotherm. The activation energy and thermodynamic parameters were calculated at different temperatures. Results showed that BCBD had a higher inhibition efficiency compared with BAPD.

Four new complexes [Nd (phen)2 (pcyd)3] (1), [Nd (phen) 2 (2-Clpcyd) 3] (2), [Nd (phen) 2 (2, 3, 5-Cl3pcyd) 3] (3) and [Nd (phen) 2 (2, 3, 4, 5-Cl4pcyd) 3] (4) where pcyd=phenylcyanamide anion, 2-Clpcyd= (2-chlorophenyl) cyanamide anion, 2, 3, 5- Cl3pcyd= (2, 3, 5-threechlorophenyl) cyanamide anion and 2, 3, 4, 5-Cl4pcyd= (2, 3, 4, 5-tetrachlorophenyl) cyan amide anion, were prepared and characterized by IR, UV-Vis and 1H NMR spectroscopy as well as elemental analysis. The 1H NMR spectra of these complexes show broadening of ligand protons attributed to coordination of paramagnetic center.

The preparation of four novel Fe (VI) salts, including PbFeO4, ZnFeO4, CdFeO4 and HgFeO4 is demonstrated. These Fe (VI) salts were synthesized from a solid phase reaction merely by grinding K2FeO4 with M (C2H3O2) 2. nH2O (M=Pb2+, Zn2+) or M (NO3) 2. nH2O (M=Cd2+, Hg2+) at room temperature. A rapid and efficient reaction occurred upon grinding the solid reactants to afford high yield ferrate (VI) salts which were characterized by XRD, EDS and FTIR techniques. All of the synthesized ferrates were rather stable and could be stored at room temperature for more than a month with no significant decomposition.

A new pendant armed Schiff base macrocyclic complex of [CdL] 2+, was prepared via cyclocondensation of 2, 6-bis (2- formylphenoxymethyl) pyridine with branched hexaamine in the presence of Cd (II) ion. The ligand was 23-membered oxaazamacrocycle having two 2-aminoethyl pendant arms [L: 3, 28-dioxa-14, 17-bis (aminoethyl) -11, 14, 17, 20, 34- pentaazatetracyclo [34.3.1] tetratriacontane-1 (34), 4, 6, 8, 10, 20, 22, 24, 26, 30, 32-undecaene]. The complex was investigated by IR, 1H NMR, microanalysis and MALDI mass spectroscopy. The structure of the complex was verified by ab initio HF-MO calculations using a standard 3-21G* basis set. This article introduces an unusual seven-membered chelate ring and shows that by its using, the Cd-N bonds lengths within the macrocycle would be longer and also Cd (II) -pendant amine bonds lengths would be shorter.

The crystal structure of 1, 10-phenanthroline-5, 6-dione ligand with Zn (II), tris (1, 10-phenanthroline-5, 6-dione) zinc (II) hexafluorophosphate, [Zn (phen-dione) 3] (PF6) 2, is reported. The complex was characterized by elemental analysis, IR, 1H NMR, electronic absorption spectroscopies, cyclic voltammetry and X-ray crystallography. Yellow crystals of [Zn (phen-dione) 3] (PF6) 2 were formed by ether diffusion into an acetonitrile solution of the complex. The title complex crystallized in monoclinic crystal system (Z=2) with space groups of P21, a=12.0299 (15) Å, b=14.5306 (19) Å, c=13.1879 (17) Å, b=94.058 (2)° and V= 2299.5 (5) Å, b. The structure was refined by using 10048 independent reflections, with I > 2s (I) to an R factor of 0.0490. Singlecrystal structure showed that the coordination geometry around the Zn (II) was a distorted octahedron. The complex showed an intense fluorescence band at visible region (690 nm) in CH3CN with an excitation wavelength of 310 nm at 25.0±0.1oC. Cyclic voltammogram of the title complex showed two quasi-reversible reduction couples at negative potential, which were assigned to the consecutive reduction of phen-dione ligand to phen-semiquinonate and phen-diolate respectively by analogy to other phen-dione complexes at scan rate 200 mV s-1.

Highly efficient production of 4-substituted-1, 2, 4-triazole-3, 5-diones from urazole derivatives using ammonium nitrate and silica sulfuric acid (SiO2-OSO3H), as a cheap and nontoxic catalyst, in the presence of wet SiO2 (50% w/w) under mild and heterogeneous conditions is reported. The process presented here is operationally simple, environmentally benign and produces high yield.

highly efficient and practical synthesis of C -terminal amidated peptides has been developed. According to this approach, amidation of the C- terminus of peptides was carried out using NH4Cl, alkylammonium chloride (RNH3Cl) and semicarbazide hydrochloride in the presence of TBTU as a coupling reagent and a tertiary amine as the base at room temperature in good to high yields. Some opioid peptides such as enkephalin derivatives were synthesized according to this novel method.

Thremogravimetric (TG) studies of a new series of organotin (IV) carboxylates of the general formula RnSnL4-n (where R=CH3, C2H5, C4H9, C6H5, C6H11 and C8H17, n=2, 3 and L=para -methoxyphenylethanoate anion) have been carried out. Horowitz and Metzger method has been used to calculate thermokinetic parameters. It has been found that diorganotin dicarboxylates have larger activation energy than those of corresponding triorganotin carboxylates. Furthermore, the activation energy, Gibb’s free energy, entropy and enthalpy of diorganotin compounds shows the following trend, (CH3) 2SnL2 < (C2H5) 2SnL2 < (C4H9) 2SnL2 < (C8H17) 2SnL2. This is attributed to steady increase in chain length of the alkyl groups. However, triorganotin compounds do not show such behavior.

A new sensitive method using high performance liquid chromatography (HPLC) and liquid extraction for the analysis of acrylamide (AA) in potato chips is reported. The method comprises extraction with acetone using ultrasonic bath and reversed phase C18-AQ (2x250 mm) column with water as eluent. Flow rate was 0.15 ml min-1 and the column temperature was kept constant at 40 °C. The analysis was performed using a 20 ml injection loop and a UV detector adjusted at 202 nm. In this condition, the retention time for AA was 8 min. A linear calibration curve (regression coefficient=0.999) in the range of 20-400 ng g-1 was used for quantitative purposes. Limit of detection (LOD) (signal-to-noise ratio of 3: 1) and limit of quantification (LOQ) (signal-to-noise ratio of 10: 1) for the method was 2.46 and 3.14 ng g-1, respectively. Extracted samples and standard solutions with different concentrations of AA were analyzed repeatedly in one day and different days to estimate the repeatability and reproducibility of the method. Analysis of variance on the obtained data showed no significant difference between variances in different days. Using the proposed method, different potato chips samples were analyzed in different days in another laboratory. Paired t-test showed no significant difference between the obtained results from the two laboratories.

An efficient synthesis of N -phenylcarboxamodo-2-aryl-1, 2-dihydro- (4 H)-3, 1-benzoxazin-4-ones is described by cyclization reaction of some 2-(benzylidene-amino) -benzoic acids with phenyl isocyanate under reflux conditions in CHCl3. Higher yields of the products were produced in high purity with simple work-up.

A specific assembly process, driven by coexisting X-H…O hydrogen bonding and X…O short intermolecular contacts (X=C, N, O) is described, in which the pseudo -Keggin polyoxoanion and two types of molecule. . . cation pairs (with C1 and Ci symmetries) were assembled to the programmed supramolecular architecture. Cooperation of the positive-charge, resonance effect and the O=C…Oterminal intermolecular contact led to the short and strong symmetrical [O…H…O]+ hydrogen bond (O…O= 2.449 (13) Å) in one of the molecule…cation pairs [C4H9NO…H…ONC4H9]+ with the H-bonded proton in the center of inversion. The other [C4 H9 NOH…ONC4 H9]+ molecule…cation pair (non-centrosymmetric) was formed through a very strong asymmetric [O. H. O]+hydrogen bond of 2.431 (13) Å in length which was created via the synergistic effect between the minor N-H…O secondary interaction, +CAHB (positive-charge-assisted hydrogen bond) and RAHB (resonance assisted hydrogen bond) mechanisms.

Some new unsymmetrical diimino tetradentate Schiff bases derived from 3, 4-diaminobenzophenone, (N-salicyliden-N'-5- OMe. salycyliden) -3, 4-diaminobenzophenone (H2sal-5-OMe. sal. dabp) (H2L1), (H2sal-5-Br. sal. dabp) (H2L2), (H2sal-5-Cl. sal. dabp) (H2L3) and (H2sal-5-NO2. sal. dabp) (H2L4) and their Ni (II) and Cu (II) complexes were synthesized and characterized by elemental analysis, IR, 1H NMR, UV-Vis spectra and mass spectra. The thermodynamic formation constants of the complexes were determined spectrophotometrically at constant ionic strength (0.1 M NaClO4) at 25oC in DMF and their free energies of formation were calculated at 25oC.

Large scale enzymatic resolution of racemic sulcatol 2 has been useful for stereoselective biocatalysis. This reaction was fast and selective, using vinyl acetate as donor of acyl group and lipase from Candida antarctica (CALB) as catalyst. The large scale reaction (5.0 g, 39 mmol) afforded high optical purities for S-(+) -sulcatol 2 and R-(+) -sulcatyl acetate 3, i. e. , ee > 99 per cent and good yields (45 per cent) within a short time (40 min). Thermodynamic parameters for the chemoesterification of sulcatol 2 by vinyl acetate were evaluated. The enthalpy and Gibbs free energy values of this reaction were negative, indicating that this process is exothermic and spontaneous which is in agreement with the reaction obtained enzymatically.

A simple and efficient one-pot synthesis of biscoumarin and 3, 4-dihydropyrano [c] chromene derivatives using catalytic amounts of SDS in water medium is reported. The catalyst can be recovered by simple filtration and reused.

Melamine trisulfonic acid (MTSA) is easily prepared by the reaction between melamine and neat chlorosulfonic acid at room temperature. This compound can be used as an efficient and recyclable catalyst for the synthesis of coumarins via von Pechmann condensation reaction under solvent-free conditions.

In the presence of low energy gamma emitter radioisotopes of thallium-201 (201Tl) or technetium-99m (99mTc), H2O2 was generated via radiolysis of water. The produced H2O2 was amperometrically determined using an anthraquinone 2-carboxylic acid modified horseradish peroxidase on glassy carbon electrode. In the presence of each radioisotope, the cathodic current produced due to the amperometric detection of H2O2, was designated as biosensor response. At the applied potential of -550 mV (vs. Ag/AgCl), the biosensor showed the sensitivities of 1.937 and 2.278 nA h mGy-1 towards H2O2 produced by 201Tl and 99mTc respectively. Finally, the calibration curves for dose rate determination of 201Tl and 99mTc have been presented and the correlations between biosensor response to H2O2 and the gamma emitter dose rates for 201Tl and 99mTc are established.

The synthesis and characterization of [Ni (BCE)] and [Cu (BCE)] (where BCE=bis (3-chloroacetylacetone) ethylenediimine) are described. The coordination geometry of [Ni (BCE)] was determined by X-ray crystallography. It was found to be planar and four coordinate in the solid state. The electrochemical properties of M (Chel), where M=Co (II), Ni (II) and Cu (II), and Chel= BAE (bis (acetylacetone) ethylenediimine), BBE=bis (benzoylacetone) ethylenediimine, BFE (bis (1, 1, 1-triflouroacetylacetone) ethylenediimine and BCE ligands were investigated in DMF and DMSO as solvents. The oxidation potentials changed from left to right in the periodic table in the trend: Co< Ni<Cu, while the reduction potentials changed according to the trend: Ni>Co >Cu. The oxidation potentials of M (II) to M (III) (M=Ni and Cu) increased according to the Schiff base ligands in the trend: BAE<BBE<BCE<BFE, while the reduction potentials followed a reverse trend: BAE>BE>BCE>BFE. The oxidation potentials of M (II) to M (III) increased according to the solvent in the trend: DMSO<DMF.

Novel copper (II) and zinc (II) complexes of the type [ML (dppz)] Cl2, [L=Schiff base derived from the condensation of 3- (3- phenyl-allylidene) -pentane-2, 4-dione and para-substituted aniline; X=-NO2 (L1), -H (L2), -OH (L3) and -OCH3 (L4); dppz= dipyrido (3, 2-a: 2 ', 3' -c) phenazine] were synthesized and characterized by various analytical and spectral techniques. The physicochemical studies and spectral data indicated that all the complexes were monomeric and cationic with square-planar geometry. Spectroscopic data and viscosity measurements showed that the complexes intercalated to DNA with large binding constants. The substituted groups such as -NO2, -H, -OH and -OCH3 in aniline moiety influenced the observed trend in the redox potentials of the complexes. The peak potential separation and formal potential of complexes were independent of sweep rate or scan rate (n) indicating a quasireversible one-electron redox process. In all the cases, ίp was linear function of n1/2, as expected for diffusion controlled process, and ίpa/ίpc » 1 at all sweep rates. It was found that the decrease in ipc was due to the higher binding of copper complexes and slowly diffusing DNA. In the presence of a reducing agent like 3-mercaptopropionic acid (MPA), the chemical nuclease activity order of the copper complexes under dark reaction condition was -NO2>-H>-OH>-OCH3. The hydrolytic cleavage of DNA by the zinc complexes was supported by the evidence from free radical quenching and T4 ligase ligation.

Conformational stabilities of the transition metal complex of the [Ni (en) 3] Cl2 was studied using Density Functional Theory (DFT). The deformational potential energy profiles (PEPS), pathways between the different isomeric conformational energies were calculated using B3LYP/6-31G. Relative conformational energies of the D(lll), D(lld), D(ldd) and D(ddd) were 0.04, 0.36, 0.17, 0.0 kcal mol-1, respectively, which were small compared to the barrier heights for the reversible phase transitions 51.12, 50.48, 49.64 kcal mol-1, respectively. The frequency assignment was carried out by fitting Fourier transform infrared (FTIR) spectra and using Gaussian and GaussView computer programs. The theoretical vibrational circular dichroism (VCD) absorption spectra are presented for all conformations in the range of 400-3500 cm-1. Calculated electron paramagnetic resonance (EPR) gtensor parameters of the [Ni (en) 3] Cl2, gx=2.69, gy=gz=2.71, are well compared to the corresponding experimental values and indicate a spherical electronic structure for the Ni atom in this compound.

A new application of the mean centering of ratio spectra method is proposed for estimation of the rate constants of second order reactions, using kinetic-spectrophotometric data. The method is based on the mean centering of the ratio spectra to obtain a kinetic profile of the product. Using computational fitting, the rate constant can be obtained without any ambiguity. An interesting feature of second-order reactions is that the number of steps in the reaction is less than the number of absorbing species, resulting in a rank-deficient response matrix. Through using row mean centering of ratio spectra, the pure response of the product of the reaction could be obtained, and thus an accurate estimation of rate constant would be possible. The applicability of the method was evaluated by using several model data. The reaction of 1, 2-naphthoquinone-4-sulfonate sodium (NQS) and 3-nitroaniline (TNA) in ethanol as a real system was also studied applying the proposed method.

N, N' -Dibromo- N, N' -1, 2-ethanediyl bis (p-toluene sulfonamide) [BNBTS] as a reusable catalyst promoted one-pot synthesis of benzo [c] acridines in good to high yields under three-component reaction from anilines, aldehydes and cyclic 1, 3-dicarbonyl compounds under solvent-free conditions.

A simultaneous preconcentration procedure for the determination of Cd (II), Ni (II), Co (II) and Cu (II) by atomic absorption spectrometry is described. The method is based on solid phase extraction of the metal ions on dithizone loaded on naphthalene in a mini-column, elution with nitric acid and determination by flame atomic absorption spectrometry. The sorption conditions including NaOH concentration, sample volume and the amount of dithizone were optimized in order to attain the highest sensitivity. The calibration graph was linear in the range of 0.5-75.0 ng ml-1 for Cd (II), 1.0-150.0 ng ml-1 for Ni (II), 1.0-150.0 ng ml-1 for Co (II) and 1.0-125.0 ng ml-1 for Cu (II) in the initial solution. The limit of detection based on 3Sb was 0.13, 0.32, 0.33 and 0.43 ng ml-1 for Cd (II), Ni (II), Co (II) and Cu (II), respectively. The relative standard deviations (R. S. D) for ten replicate measurements of 20 ng ml-1of Cd (II), 100 ng ml-1 of Ni (II), Co (II) and 75 ng ml-1 of Cu (II) were 3.46, 2.43, 2.45 and 3.26%, respectively. The method was applied to the determination of Cd (II), Ni (II), Co (II) and Cu (II) in black tea, tap and river water samples.

Several new chiral oxazolines were prepared conveniently in good to high yields using a two-step synthesis involving formation of an optically active amide, in situ conversion of the amide into tosylate (OTs) and finally ring closing reaction under MW irradiation (800 W) in solvent free condition. A comparison of these results with those obtained from the ring closing reaction under classical conditions was also made.

A new lead coordination polymer [Pb (aip)]n (H2aip=5-aminoisophthalic acid) was synthesized and characterized by IR, elemental and X-ray single-crystal analyses. X-ray crystallographic study of this complex revealed that H2aip ligand adopts a new coordination mode different from any reported modes in the title complex. The thermogravimetric experiment was carried out to examine the thermal stability, and the photoluminescence property of the title complex was investigated.

The aim of this study was to investigate order-disorder in the two-dimensional AB alloy to find out whether the number of components, N A and N B, was equal or not. To this end, using the nearest neighbor interactions, first, we applied a two-dimensional lattice which consisted of infinite rows, R and columns, L, so that, RL=N A+N B. For such a model, using the combinatorial factor method, we derived an exact equation for the partition function. Because, the derived partition function was very complicated, the thermodynamic properties of the lattice could not be calculated; however, but these properties could be estimated for the models with a limited number of rows. Our results show that, for models with finite number of rows, for each mole fraction of A in the specific temperature, a phase transition, like Onsager transition, takes place.

The cationic halochromism of phenolate betaines was reproduced with the aid of a simple theoretical model, by calculation of the longest wavelength transition energies of supermolecules obtained by positioning a cation Mn+at a variable distance from the oxygen atom of the dye. The theoretical results were compared with experimental data for three systems, Reichardt’s betaine 1, Brooker’s merocyanine 2 and the N-methyl-8-oxyquinolinium dye 3. The model was validated by molecular dynamics simulations of solutions of dye 3, in methanol and DMSO, in the presence of variable concentrations of Na+.

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 lmax=270 nm. This method made it possible to quantitize HCT in the range of 0.1-21.0 mg 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.

Molecular fragments variable connectivity index (mfVCI) is proposed as a variable molecular descriptor. Having in mind that the molecular structure unit exerts strong effect on the boiling point, molecular fragments could be defined as the atoms or functional groups having different characteristics due to different chemical bonding. Each molecular fragment is regarded as a vertex of topological diagram endued with variable weights to substitute for topological matrix diagonal. The quantitative structure-property relationship (QSPR) model, obtained by mfVCI, shows its desirable robustness and predictivity.

The formation constants of some oxovanadium (IV) binary complexes containing Schiff bases resulting from condensation of salicylaldehyde with aniline and with its derivatives were determined spectophotometrically. The synthesized compounds were characterized by analytical and different physico-chemical techniques like 1H NMR, IR, elemental analysis, mass and UV-Vis spectral studies. The IR spectra affirm that coordination takes place through azomethine nitrogen and phenolate oxygen. Three of the VO (IV) Schiff base complexes i. e. bis (salicylideneaniline) oxovanadium (IV), [VO (L1) 2], bis (salicylidene-4-methoxyaniline) oxovanadium (IV), [VO (L2) 2] and bis (salicylidene-4-cyanoaniline) oxovanadium (IV), [VO (L10) 2], were studied by thermogravimetry in order to evaluate their thermal stability and thermal decomposition pathways. The number of steps and, in particular, the starting temperature of decomposition of these complexes depends on the equatorial ligand. The complexes screened for antioxidant activity and the ab initio calculations were carried out to determine the structural and the geometrical properties of a typical vanadyl salicylideneaniline complex, [VO (L1) 2].