Synthesis and characterisation of bis(pentafluorophenyl)antimony(V) cations, [(C6F5)2SbL3]

Pentacoordinate complex cations of the general formula [(C₆F₅)₂SbL₃]³⁺ stabilized as solid salts in combination with tetraphenylborate (BPh₄), tetrafluorobroate (BF₄) anions, where L=DMSO, Ph₃AsO, PyO, DMF, α-, β- and γ-picoline have been isolated. The newly formed complexes were characterized by elemental analysis, molar conductance measurements, solid-state IR and and NMR. From these results, a five-fold coordination around antimony was required.     

Effect of the rate of diffusion of ions on the periodic precipitation of silver chromate

The effect of the rate of diffusion on the formation ofLiesegang rings of silver chromate in gelatin and agar agar medium has been studied. The rate of diffusion of silver ions in the agar agar gel is much slower than that in gelatin gel during the formation of rings of silver chromate. If the rate of diffusion of silver ions in agar agar gel is increased, even then rings do not form. The only change brought about by the rate of diffusion is for the distance between the successive rings.

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Zusammenfassung Der Einflu\ der Diffusionsgeschwindigkeit auf die Bildung vonLiesegang-Ringen aus Silberchromat in Gelatine und Agar-Agar wurde untersucht. Die Diffusionsgeschwindigkeit der Silberionen in den Agar-Agar-Gelen ist viel niedriger als in den Gelatinegelen während der Bildung der Ringe von Silberchromat. Wenn die Diffusionsgeschwindigkeit der Silberionen in Agar-Agar-Gelen gesteigert wird, bilden sich schlie\lich überhaupt keine Ringe. Der einzige Einflu\, den die Diffusionsgeschwindigkeit hervorruft, ist also änderung des Abstandes aufeinanderfolgender Ringe.

     

Studies on some newer polyhydrazides containing amide linkages. III

Novel polyhydrazides having inherent viscosities in the range of 0.24–0.38 dL g^?1 were prepared by polymerizing a series of hydrazides with different diacid chlorides in polar aprotic solvents. These polymers display a wide range of solubility in a number of solvents. They start decomposing at about 200°C in air. Results of differential thermal and thermogravimetric analysis show that a steep weight loss takes place mainly in the range of 300–440°C.     

Dynamic light-scattering analysis of the electrostatic interaction of hexahistidine-tagged cytochrome P450 enzyme with semiconductor quantum dots.

Currently, there is great interest in the development of methods suitable for determining the stoichiometry of biomolecules attached to nanoparticles. We describe the use of the dynamic light-scattering technique (DLS) to determine the stoichiometry of the protein cytochrome P450(BSbeta) attached to CdS and CdSe quantum dots (QDs). The enzyme-conjugated QDs have different diffusion characteristics compared to the QD and enzyme precursors, expressed in their size, scattering intensity as well as zeta-potential values. The significant enhancement of the scattering intensity of QDs observed upon conjugation with the P450(BSbeta) due to the refractive-index increment and the systematic variation in zeta potential resulting from charge neutralization of the anionic QDs by the cationic histidine-tagged P450(BSbeta) have been used for stoichiometry determination.     

Kinetics of polymerization of acrylonitrile initiated by the Mn3+-thioacetamide redox system

Kinetics of the polymerization of acrylonitrile has been investigated in aqueous sulfuric acid in a temperature range of 25–45°C. The rate of polymerization (R_p) and the rate of managanic ion disappearance, etc., have been measured. The effect of the various additives, such as water-miscible organic solvents, neutral electrolytes, complexing agents, and surfactants, on the rate has been thoroughly studied. A mechanism that involves the initial complex formation between the thiol form of the thioamide and Mn³⁺, whose decomposition yields the initiating free radical with the polymer chain terminated by mutual combination of growing radicals, has been suggested.     

Influence of the nature of organic diluents on the extraction of uranium(VI) by bis(2-ethylhexyl) sulfoxide from nitric acid solutions

The extraction of uranium(VI) from nitric acid solutions by bis(2-ethylhexyl) sulfoxide (BESO) has been examined using sixteen inert organic diluents in order to establish the correlation between its distribution coefficient and some physico-chemical properties of the diluents. The extracted solvated species is shown to be UO₂(NO₃)₂·2BESO, irrespective of their nature. The extraction rate is lower in halogen substituted hydrocarbons as compared to the other diluents used. Among benzene derivatives, extraction is found to decrease with number of substituted methyl groups. Extraction efficiency decreases as the organic solvent is varied in the order: benzene>nitromethane>toluene> >nitrobenzene>cyclohexane>p-xylene>monochlorobenzene>dodecane>o-dichlorobenzene> >hexane>decalin>1,2-dichloroethane>1,1,1-trichloroethane>carbon tetrachloride> >tetrachloroethane>chloroform. Among the properties showing good correlations with distribution coefficient are Hansen's three-dimensional solubility parameters and Dimroth's empirical solvent polarity parameters [E _T(30) ]. Polarizability indices are most satisfactorily applicable to a wide variety of solvents.     

Determination of gallium in tumour-affected tissues by means of spectroscopic techniques

A comparative investigation was carried out on the suitability of atomic absorption spectrometry and of emission spectrography with arc and hollow-cathode excitation sources for determination of gallium (μg g^-1) in biological samples. The three methods give reliable results. Hollow-cathode emission spectrography was found to be influenced to a lesser extent by matrix effects and to be more precise than the other two techniques.