Thermal and spectral studies on complexes derived from tetradentate Schiff bases

Several new complexes of Schiff bases ligands H₄La and H₄Lb with transition metal ions such as Cr(III), Fe(III), Co(II) and Zn(II) are synthesized. Elemental analysis, infrared, UV–Vis and thermal analysis, as well as conductivity and magnetic susceptibility measurements are used to elucidate the structure of the newly prepared metal complexes. A square planar geometry is suggested for Zn(II) complexes, while an octahedral geometry suggested for the Cr(III), Fe(III) and Co(II) complexes. The thermal decomposition of complexes was found to be first order reaction and the thermodynamic parameters corresponding to the different decomposition steps were reported.     

Thermodynamics of the solvent extraction of Zr(IV) by Amberlite LA-2, TBP and HDEHP from different aqueous media

Solvent extraction on Zr(IV) were carried out at 5, 25 and 40 °C using Amberlite LA-2, TBP and HDEHP in toluene or kerosene from solutions of HCl, HBr or KI. The equilibrium constant K _ex as well as the thermodynamic functions DG°, DH° and DS° of the nine extraction systems were deduced. The overall extraction equilibria were postulated from the obtained data.     

Anti-Alzheimer and Anti-COX-2 Activities of the Newly Synthesized 2,3′-Bipyridine Derivatives (II)

3-Amino-4-aryl-6-pyridin-3-ylthieno[2,3-b]pyridine-2-carbohydrazides 3a,b were used as the starting materials in the present study. Our targets here were represented by the synthesis of several 3-amino-N′-4-arylmethylenes 5a,b, N-formamides 8a,b, ethyl imidoformate 10b, N,N-dimethyl-N′-imidoformamides 12a,b, N-acetyl-N-acetamides 14a,b, 1,3,4-oxadiazole-2-thiol 16a,b, pyrazolothienopyridines 20a,b, 2-[(3,5-dimethyl-1H-pyrazol-1-yl)carbonyl]-4-aryl-6-pyridin-3-ylthieno[2,3-b]pyridin-3-amines 22a,b, 2-carbonyl-5-methyl-2,4-dihydro-3H-pyrazol-3-ones 24a,b, and 2-carbonyl-pyrazolidine-3,5-diones 26a,b. The newly synthesized heterocyclic compounds were tested as anti-Alzheimer and anti-COX-2 agents, and their structures were elucidated by considering the data of IR, ¹H NMR, mass spectra, and elemental analyses.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Utilization of 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) for kinetic spectrophotometric assay of befunolol hydrochloride in its pharmaceutical formulation

A simple, accurate, precise, and sensitive kinetic spectrophotometric method for determination of befunolol hydrochloride is described. The method is based on the formation of a colored product with 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) in methanol at 70 degrees C for 45 min. The red-colored product was measured at 523 nm. The optimization of various experimental conditions is described; Beer's law was obeyed in the range 15.25 x 10(-6) to 122.04 x 10(-6) M. The results obtained showed good recoveries (100.1 +/- 0.80%). Application of the proposed method to a pharmaceutical formulation was successfully achieved. The determination of befunolol hydrochloride by fixed time, fixed concentration, and rate constant methods was feasible with the calibration equation obtained. However, the fixed time method proved to be more applicable.     

Solubility and thermodynamic studies of sparingly soluble tellurite salts

Journal of Thermal Analysis and Calorimetry - In the past few years, tellurium has attracted much attention as it is widely used in a large number of important industrial applications. Despite its...     

New and selective HPTLC—Densitometric method for determination of pioglitazone hydrochloride

JPC – Journal of Planar Chromatography – Modern TLC - New sensitive and selective HPTLC-densitometric method has been developed for the determination of pioglitazone hydrochloride. The...     

Surface layer-by-layer chemical deposition reaction for thin film formation of nano-sized metal 8-hydroxyquinolate complexes

The feasibility of a novel and simple layer-by-layer chemical deposition method for the preparation of nano-sized metal 8-hydroxyquinolate complexes has been investigated and reported. Uniform nanocrystalline films have been synthesized via dipping a substrate alternately in metal ion solution followed by ligand solution. The stoichiometry of the as-grown anhydrous Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complex crystals were confirmed from the metal analysis and molar stoichiometric ratio of metal ion to 8-hydroxyquinoline. This was characterized as 1:2 for the Co(II), Ni(II), Cu(II) and Zn(II)–quinolate complexes. The Fe(III)–quinolate thin film was found to exhibit a 1:3 ratio. Electron impact-mass spectra (EI-MS) of all the synthesized thin film metal quinolate complexes were recorded and the results refer to the existence of the molecular ion peak at the corresponding m/z values. Confirmation of such stoichiometric 1:2 and 1:3 ratios were also evident from the (EI-MS) study. The deposited thin films were also subjected to analysis by a scanning electron microscope (SEM) and a particle size ?50 nm was detected. FT-IR and UV–Vis spectroscopy were further used to confirm the structure of the metal 8-hydroxyquinolate complexes. Thermal gravimetric analysis (TGA) was also used to follow up the possible thermal decomposition steps and to calculate the thermodynamic parameters of the nano-sized metal complexes.     

Analytical model for dust generated by air-cushion vehicles

The air-cushion vehicle (ACV) is widely used over unconsolidated soils and rugged terrain. This off-the-road vehicle can have mobility problems as well as cause environmental problems. Most of these problems cannot be fully controlled but measures can be taken to minimize their effect. Two of the mobility problems are dust generation and ground surface erosion. This research is a continuation of previous attempts at understanding the mechanics of dust generation and the evaluation of parameters representing soil resistance to disturbance under the air cushion pressure. Specifically this research provides a comprehensive analytical approach by which the characteristics of ACV dust raising, residence time and sedimentation rates are evaluated. Stoke's Law is used in this analysis with concomitant practical assumptions. Field utilization of these models is developed, and predetermination of dust size distribution above ground level, as well as possible particulate dispersions during the dust raising stage are reported. With this information the dust distribution and amount of dust in the atmosphere can be predicted at any time and at any elevation above the ground. Relationships between the quasi-theoretical analyses and the experimental results were considered and found to be in good agreement.