A. M. El-Atrash

Charge transfer complexes of some thiazoles and benzothiazoles with certain nitrobenzene derivatives

Abstract Interaction of some thiazole and benzothiazole derivatives as donors with certain di- and trinitrobenzene derivatives as acceptors results in the formation of 1:1 molecular species. The infrared, NMR and ultraviolet analysis of the complexes with non-acidic acceptors reveals the presence of π-π* interaction from a HOMO of the thiazole nucleus or the phenyl moiety of the benzothiazoles to a LUMO of the benzene ring of the acceptors. The existence of this type of interaction is supported by HMO calculations on the donor molecules. On the other hand, the molecular complexes derived from acidic acceptors are stabilized, in addition to the π-π* interaction, by proton transfer from the hydroxyl or carboxylic group of the acceptor to the amino group of the aminothiazole donors. The ionization potentials of donors, electron affinities of acceptors as well as the energy of the CT complexes were computed from their u.v. and visible spectra.

Temperature effects on the synergistic solvent extraction of cobalt(II)

The extraction of Co2+ from a 0.1M ionic strength acetate buffer by acetylacetone, and a mixture of acetylacetone and pyridine or triethylamine was investigated at various temperatures. The enthalpy and entropy change data for the synergistic extraction support a model in which the Co2+ ion in the acetylacetonate complex expands its coordination number from four to six in order to accomodate the two N-base molecules. The steric hindrance caused by triethylamine is also reflected in the thermodynamic data.

The direct current electrical conductivity of the charge transfer complexes of some thiazoles and benzothiazoles with certain di- and trinitrobenzene derivatives

Abstract The DC electrical conductivity of 2-aminothiazole ( I ), 2-aminobenzothiazole ( II ), 2-amino-4-methylbenzothiazole ( III ) and 2-amino-6-nitrobenzothiazole ( IV ) and their charge transfer (CT) complexes with the acceptors, 1,3-dinitrobenzene ( 1 ), 3,4-dinitrobenzoic acid ( 2 ) and picric acid ( 3 ) were investigated. The positive temperature coefficients of the electrical conductivity of these thiazoles suggested their semiconducting characteristics. The CT complexes were classified into two main groups. The first group included the complexes I 1 , I 2 and IV 1,2,3 . All these complexes had negative temperature coefficients of resistance and revealed conventional semiconducting behaviour. Two different activation energies for the complexes I 2 , IV 2 and IV 3 indicated the presence of more than one conduction mechanism. The second group contained the complexes I 3 , II 1,2,3 . and III 1,2,3 . The thermal conductivity plots exhibited curves with two inflections and three regions. The slope of the line of a region and also its temperature range were found to depend upon the nature and structure of the complex. No correlation was found between the activation energies of the CT complexes and either the electron affinities of acceptors or the ionization potentials of donors. This was explained by assuming that the geometrical, and not the electronic, structure of the complexes was the determining factor.

Polarographic behavior of copper ion in solution of o-carboxyphenylazo-acetylacetone

Abstract Copper acetate at pH 6.0 in dioxane-water solvent 25% gives with o -carboxyphenylazo-acetylacetone only one complex of composition 1:1. This complex is reduced at the dropping mercury electrode in solutions of 0.1 M sodium sulphate giving a single irreversible diffusion controlled wave corresponding to two-electron reduction. The half-wave potential of this wave is pH dependent, both in non-buffered and in acetate buffer solutions, and shifts to more negative values by increasing the pH of the solution. The relation between copper concentration and the height of the wave of the complex is linear. An amperometric titration method was given for determining the concentration of copper ion in solution.

Solvent effects in the synergistic solvent extraction of Co2

The extraction of Co2+ from a 0.1M ionic strength aqueous phase (Na+, CH3COOH) of pH=5.1 was studied using thenoyltrifluoroacetone, HTTA, in eight different solvents and HTTA+trioctylphosphine oxide, TOPO, in the same solvents. A comparisons of the effect of solvent dielectric constants on the equilibrium constant shows a synergism as a result of the increased hydrophobic character imparted to the metal complex due to the formation of the TOPO adduct.

Ionic strength effects in the synergistic solvent extraction of Co2

The extraction of Co2+ by a mixture of acetylacetone (acac) and pyridine (py) from an aqueous phase of varying ionic strengths has been investigated. The extraction studies were done at different temperatures in order to determine the effect of changes in the ionic strength on the free energy ΔG, enthalpy ΔH and entropy ΔS of the synergistic reaction.

Thermodynamics of the extraction of Europium (III) radiotracer by benzyl-phosphonic acid monoester

The extraction of Eu3+ from perchloric acid by ethyl hydrogen benzyl phosphonate (HEBP) dissolved in a series of organic diluents, has been studied at different temperatures. From the variation of the distribution ratio with temperature, the thermodynamic functions ΔH, ΔS and ΔG have been determined. The meaning of the experimentally obtained thermodynamic quantities is discussed.

Study of the surface properties of titanium hydroxide using a radioactive tracer technique

The surface properties of titanium hydroxide precipitates, formed under different conditions were studied in the presence of carrier-free radioactive89Sr. It was found that titanium with concentrations equivalent to 24 mg TiO2/litre, was enough to remove by adsorption more than 95% of the carrier-free strontium activity from an alkaline solution (pH≈13) in less than 6 hrs, regardless of whether the precipitate was freshly prepared or aged for a few days. If the precipitate was formed in situ, at the above pH value, the percentage removal of the strontium activity from the solution was even greater, and this was attributed to an internal adsorption process. At a lower pH value (∼2.5), however, the adsorption of strontium activity by titanium hydroxide was very low (<5%), whether the precipitate was preformed or formed in situ. The increase in the adsorption ability of titanium hydroxide precipitate on going from low pH (2. 5) to higher values was attributed to the inversion of the charge of titanium hydroxide sols from cationic particles at pH 2. 5 to negatively-charged particles at pH>3. 5, these latter particles adsorbing any positive strontium ions in solution.

The synergistic effect of 2-benzoyl- and 2-anilinopyridine on the extraction of certain europium phosphonate complexes

Extraction of Eu(III) ethylbenzylphosphonate or Eu(III) ethylbenzoylphosphonate complex in n-hexane solvent is found to be greatly enhanced in the presence of 2-benzoylpyridine as a synergist. Also, the extraction of Eu(III) ions is enhanced to a smaller extent by a mixture of ethylhydrogenbenzylphosphonate and 2-anilinopyridine. An antagonistic effect is observed in the extraction of europium by the ethylhydrogenbenzoyl-phosphonate and 2-anilinopyridine mixed system. The stoichiometry of the formed complexes is found to be dependent upon the type of synergist employed. This can probably be attributed to the difference in basicity of the two reagents. The equilibrium and formation constants of the extracted complexes as well as the synergistic factors are also reported.

Extraction of praseodymium (III), europium (III), and erbium (III) from nitrate solution by ethyl hydrogen benzyl phosphonate

Abstract The extraction of Pr 3+ , Eu 3+ , and Er 3+ from aqueous nitrate solutions by ethyl hydrogen benzyl phosphonate (HEBP) dissolved in six different organic solvents was studied. The extradant, hydrogen ion, and nitrate dependencies were found to be 2.0, 2.0, and 1.0 power, respectively, HEBP was found to be a good extradant for separation of these three lanthanide ions by varying the pH.