Journal of the Iranian Chemical Society
Volume:5 Issue: 2, June 2008

Both ZrCl4 and ZrOCl2.8H2O are commercially available solid chemicals. Due to their low toxicities (LD50 [ZrCl4 oral rate] = 1688 mg/kg), (LD50 [ZrOCl2.8H2O oral rate] = 2950 mg/kg), low costs, ease of handling, high activity, the zirconium(IV) compounds are potential green catalysts or reagents which are of importance from different views. In this review we have paid attention to the applications of these compounds as reagents or catalysts in Friedel-Crafts reactions, Fries rearrangements, reduction and oxidation reactions, cycloaddition and hydrometalation reactions, protection and deprotection of functional groups, reactions of epoxides, iodination of alcohols, S-alkylation of thiols with alcohols, Michael addition, condensation of indoles with carbonyl compounds, Claisen ester condensation, Baylis-Hillman reaction, preparation of organozirconium compounds and some other miscellaneous reactions.

Our research group has been interested in synthesis of proton transfer compounds as new supramolecular synthons for the one-pot preparation of self-assembled transition metal complex-organo-networks since 2000. We have focused on the proton delivery from acids, which are considered as suitable proton donors, to amines as proton acceptors. The results were production of several proton transfer ion pairs possessing some remaining donor sites applied for coordination to metallic centers in preparation of metal-organic structures. Some of the complexes showed contributions of both cationic and anionic fragments of the starting ion pair, while some others contained only one of these species as ligand. Much of the investigations on reviewed compounds focused on the concept of supramolecular systems, co-crystallization, stereochemically active lone pairs, coordination polyhedron and mainly on various interactions involve including van der Waals, ion pairing, hydrogen bondings, face to face π-π stackings and edge to face C-H···π, C-O···π, N-H···π, S-O···π, Ti···π and Hg-Cl···π interactions. The mentioned interactions are the most commonly used strategies in the extension of supramolecular structures.

Novel phosphoramidates 8a-b possessing structural features similar to nucleoside phosphonates HPMPA, PMEA, PMEG, and oxathiolane nucleoside BCH-189 were synthesized by chemical methods. The designed molecules exhibited significant antiviral activities. We hypothesized that, as a masked membrane-soluble form of the potential bioactive compounds 7a-b, phosphoramidates 8a-b may act as a proteinase substrate. Then, the potential drug 7a-b will be liberated inside the infected cells. The triphosphate anabolites of each could act as competitive substrates for the HIV reverse transcriptase and terminate DNA synthesis after being incorporated into the growing DNA strand. Phosphoramidates 8a-b were synthesized as racemates to allow access to both enantiomers.

Chiral furyl substituted carbinols were prepared from the related carbonyl compounds and their enzymatic kinetic resolution was studied by using porcine pancreatic lipase (PPL) in transesterification reaction under solvent free condition. This study revealed that carbinols having one less bulky group on the chiral center are good substrates for PPL and the resolution proceeds with higher ee,s and less reaction time.

Rapid and efficient oxidation of Hantzsch 1,4-dihydropyridine with Potassium peroxomonosulfate is reported. The Mn(III)-salophen/monopersulfate catalytic system converts 1,4-dihydropyridines to their corresponding pyridine derivatives at room temperature in a 1:1, CH3CN/H2O mixture. The ability of various Schiff base complexes in the oxidation of 1,4-dihydropyridine was also investigated.

A chelating ion exchange resin was synthesized from 8-hydroxyquinoline and catechol using formaldehyde as a cross linking agent at 120 ± 2 °C in DMF solution. The resin was characterized by FTIR and elemental analysis. The morphology of the synthesized resin was studied by optical photograph and scanning electron microscopy (SEM). Various kinetic parameters such as energy of activation (Ea), enthalpy of activation (H‡), entropy of activation (S‡), free energy of activation (G‡), order of reaction (n) and pre-exponential factor (A) of various steps of thermal decomposition have been calculated from thermogravimertic results. The physico-chemical properties of the resin have been studied. The total cation exchange capacity was measured and effect of pH and metal ion concentration on ion exchange capacity were studied. The rate of cation exchange reactions and distribution co-efficient values in tartaric acid media at different pH were also studied using batch equilibration method.

A series of novel bis-chalcones 3 were prepared by the reaction of 5,5''-methylene-bis-salicylaldehyde 2 with various acetophenones, subsequent treatment of 3 with thiourea or guanidine resulted to the corresponding bis-thiazines or bis-pyrimidines in good yields. All the new compounds have been characterized by IR, 1H NMR, MS and elemental analysis. The antibacterial, antifungal and anti-inflammatory activities of the compounds have also been evaluated.

Nanometer MCM-41 molecular sieve was prepared under a base condition by using cetyltrimethylammonium bromide as template and tetraethyl orthosilicate as silica source by means of hydrothermal method. Lanthanum(III) was incorporated into the nanometer MCM-41 by a liquid phase grafting method. The prepared nanocomposite materials were characterized by means of powder X-ray diffraction, spectrophotometric anaylsis, Fourier transform infrared spectroscopy, low temperature nitrogen adsorption-desorption technique, solid diffuse reflectance absorption spectra and luminescence. The powder X-ray diffraction studies show that the nanometer MCM-41 molecular sieve is successfully prepared. The highly ordered mesoporous two-dimensional hexagonal channel structure and framework of the support MCM-41 is retained intact in the prepared composite material La-(nanometer MCM-41). The spectrophotometric anaylsis indicates that lanthanum exists in the prepared nanocomposite materials. The Fourier transform infrared spectra indicate that the framework of the MCM-41 molecular sieve still remains in the prepared nanocomposite materials and some framework vibration peaks show blue shifts relative to those of the MCM-41 molecular sieve. The low temperature nitrogen adsorption-desorption indicates that the guest locates in the channel of the molecular sieve. Compared with bulk lanthanum oxide, the guest in the channel of the molecular sieve has smaller particle size and shows a significant blue shift of optical absorption band in solid diffuse reflectance absorption spectra. The observed blue shift in the solid state diffuse reflectance absorption spectra of the lanthanum-(nanometer MCM-41) sample show the obvious stereoscopic confinement effect of the channel of the host on the guest, which further indicates the successful encapsulation of the guest in the host. The La-(nanometer MCM-41) sample shows luminescence.

The formation of an ordered arrangement of C60 molecules as path-like structures on the surface of highly oriented pyrolytic graphite (HOPG) is reported for the first time with theoretical implementations. Fullerene nucleation and deposition from solutions with different concentrations of C60 is performed under ambient conditions without electrochemical processes. Scanning tunneling microscopy (STM) is used to study the surface topography. The results reveal new aspects of fullerene deposition that can potentially aid in modeling with theoretical simulations.

We highlight the heterogeneity and electro-catalysis of multi-walled carbon nanotubes which is shown to be dependant on batch to batch variation via the use of cyclic voltammetry, X-ray photoelectron spectroscopy and transmission electron microscopy. Batch to batch variation is often an overlooked parameter which may limit their use in electrochemistry, and in particular, in the development and realisation of commercial electroanalytical sensors and therefore needs to be considered.

Thermodynamic properties of CO2 are derived from speed of sound in the temperature range 300 to 360 K (from 0 to 6 MPa), and 300 to 220 K (from 0 to 90% of the saturation pressure). The density, the specific heat capacity at constant pressure, and the specific heat capacity at constant volume are obtained by numerical integration of differential equations connecting the speed of sound with other thermodynamic properties. The set of differential equations is solved as the initial value problem, with the initial values specified along the isotherm at 300 K in terms of several accurate values of the density and the specific heat capacity at constant pressure. The density, the specific heat capacity at constant pressure and the specific heat capacity at constant volume are derived with the absolute average deviations of 0.018%, 0.19%, and 0.18%, respectively. The results of numerical integration are extrapolated to the saturation line for ρ, cp, and cv with the absolute average deviations of 0.056%, 2.31%, and 1.32%, respectively.

The present work describes a rapid and accurate amperometric technique for the determination of acetaminophen (ACT) in pharmaceutical preparations and human blood serum, based on electrocatalytic oxidation of ACT at a glassy carbon electrode modified by cadmium pentacyanonitrosylferrate (CdPCNF) film. The electrocatalytic response of the modified GC electrode was linear over the concentration of 1.64-52.90 µM. The limit of detection was found to be 2.04 µM by amperometric technique. The method was successfully utilized for the determination of ACT in various pharmaceutical preparations and the results have been statistically compared with those obtained by the official method. The interference of some pharmaceutical and biological compounds was investigated. The results of interference study showed that the Nafion-coated CdPCNF|GC electrode can be utilized as a selective amperometric sensor for acetaminophen determination in human blood serum. The mean value of rate constant k for catalytic reaction, and the diffusion coefficient of ACT (D) in the phosphate buffer solution of pH 7.2 were found to be 4.27 × 102 M-1 s-1, and (4.25 ± 0.33) × 10-6 cm2 s-1, respectively.

SC-84536, a selective inhibitor of inducible nitric oxide synthase (INOS), is targeted for the treatment of osteoarthritis, neuropathic pain and asthma. This report describes our effort toward developing an alternative synthetic route for preparation of SC-84536. In the process, we also developed a new and simple method for the preparation of phthalimide 6, a potentially useful synthon.

The critical micelle concentration (CMC) of hexadecylpyridinium bromide (HDPB) is determined conductometrically in binary mixtures of water + cosolvent at various temperatures and at low concentrations of sodium bromide, ranging from 0 to 2.4 × 10-2 M. Dimethylsulfoxide (DMSO) and acetonitrile (AN) were used as cosolvents added to water. The ability of NaBr to lower the CMC of HDPB in water is inhibited by DMSO and AN. Thermodynamic parameters of micellization DHm°, DSm°, and DGm° are evaluated according to the pseudo-phase model. The contribution of DMSO and AN in the micellization process of HDPB in aqueous electrolyte solutions are discussed in terms of the observed thermodynamic properties.

A new spectrophotometric method for the assay of hydralazine hydrochloride in bulk and dosage forms has been developed. The procedure is based on a condensation reaction between alcoholic solution of hydralazine and acidic solution of p-dimethylaminobenzaldehyde to generate an instant greenish-yellow coloured product. The hydrazone formed absorbed visible light strongly and optimal detector response was obtained at a wavelength of 470 nm with a molar absorptivity of 3.652 × 103 l mol-1 cm-1. Optimization of temperature and time revealed 30 °C and 10 min as the best conditions for optimal color formation, while methanol was found to be the most suitable alcohol as diluting solvent. The reaction product is stable for at least 24 h. Beer''s law was obeyed in the concentration range of 2-10 μg ml-1. Recovery studies over three days gave a mean recovery of 101.87% with a relative standard deviation of 1.29%. There was no interference from commonly used tablet excipients. There was no significant difference between the results obtained with the new method and the BP iodimetric method (p > 0.05). The proposed method is simple, sensitive, rapid and economical, and could find application as an in-process quality control method for hydralazine.

A rapid, accurate and sensitive method for the determination of captopril in human plasma was developed by solid phase extraction and high performance liquid chromatography (HPLC), using precolumn derivatization of captopril with chromophore label o-phethaldialdehyde (OPA). The extraction of captopril from human plasma was carried out by an amino propyl cartridge. A 0.01 M solution of HCl in methanol showed the best recovery and was chosen for elution of captopril in cartridge. This methanolic solution was applied to react with aqueous solution of OPA and glycine as a coderivatization reagent. The process of derivatization was completed within 2 min at room temperature. The derivatized captopril was injected into a reverse phase HPLC system. Mobile phase was consisted of water:acetonitrile:trifluoroacetic acid (85:15:0.1 v/v/v) with a flow rate of 1 ml min-1 and detector was used at 345 nm. Linear dynamic range and limit of detection were found as 0.1-6 ppm and 0.1 ppm, respectively.

The oxovanadium(IV) complexes (I) of the type [VO(L)]SO4 have been prepared using an in-situ method of synthesis with ligands derived from di-2-thienylethanedione with 1,2-diaminobenzene or 2,3-diaminopyridine. These parent complexes have been further reacted with β-diketones to yield macrocyclic complexes (II) of types [VO(mac)]SO4 (where mac = macrocyclic ligands derived by condensation of amino group of parent complex with β-diketones), wherein the VO2+ cation acts as a template.� Tentative structures of these complexes have been proposed on the basis of elemental analysis, electrical conductance, magnetic moments and spectral (infrared, electronic and electron spin resonance) data. The oxovanadium(IV) complexes are five coordinated wherein the tetraaza macrocyclic ligands act as tetradentate chelating agents. All the complexes are found to inhibit the infectivity of potato virus X, when checked using the test plant Chenopodium amaranticolor.

Inductively coupled plasma atomic emission spectroscopy (ICP-AES) with internal standardization was applied for the analysis of an in-house reference platinum alloy containing palladium and rhodium (approximately 5% by weight). In order to compensate for variations in signal recovery due to matrix interferences, and therefore to improve the precision, platinum, the major component, was chosen as an internal standard. Quantitative analysis was based on calibration using a set of matrix-matched calibration standards with and without employing the internal standard. These results were compared with those obtained by X-ray fluorescence (XRF) spectroscopy. The results for both techniques were in a good agreement, although the precision was slightly better in the ICP-AES technique, with or without the internal standard.

The title complex, [Ce(DMSO)2(H2O)Fe(CN)6] (1), was obtained by solution reactions and structurally characterized by X-ray diffraction. The title complex is characteristic of a novel cyano-bridged two-dimensional stair-like layered structure. The magnetic property of the title complex is reported herein. The χMT value at 300 K is ca. 0.92 emu K mol-1. The temperature dependence behavior of molar magnetic susceptibility of the complex clearly indicates the presence of an antiferromagnetic interaction.

This study was conducted to assess the removal efficiency of fast green FCF (a dye) from aqueous medium using the photo-Fenton process. Fenton''s reagent, a mixture of hydrogen peroxide (H2O2) and ferric ions (Fe3+), used to generate hydroxyl radicals (·OH), was used to attack the target contaminant and degrade it. A visible light source was used to provide the radiation needed in the photo-Fenton method (i.e. H2O2/Fe3+). The effects of varying the parameters of ferric ion, fast green FCF and hydrogen peroxide concentrations, as well as pH, and light intensity on the reaction rate were determined. More effective and faster than Fenton''s reagent in removing fast green FCF, the results show that the photo-Fenton method completely oxidizes and degrades fast green FCF into CO2 and H2O. A tentative mechanism for photobleaching of the dye is proposed.