Effective luminescence quenching of tris(2,2-bipyridine)ruthenium(II) by methylviologen on clay by the aid of poly(vinylpyrrolidone)

Electron-transfer quenching of tris(2,2-bipyridine)ruthenium(II) by methylviologen in an aqueous suspension of clay in the presence of poly(vinylpyrrolidone) was investigated. The quenching behavior of the excited tris(2,2-bipyridine)ruthenium(II) on clay by the coadsorbed methylviologen indicated the homogeneous distribution of the adsorbed dyes. The quenching rate was high when the clay with larger particle size was used as the host. The adsorption of poly(vinylpyrrolidone) on clay resulted in the coadsorption of the tris(2,2-bipyridine)ruthenium(II) and methylviologen without segregation.     

Study of the oxidation of diphenylamine and o-dianisidine by technetium(VII) catalyzed by copper(II). Analytical applications

Interactions between technetium and diphenylamine or o-dianisidine are described. It was found that the oxidative processes that occur between Tc(VII) and these reagents are catalyzed by the Cu(II) ion. The reactions have been investigated and, as a consequence, kinetic methods for technetium determination are developed (0.4–4 ppm using diphenylamine and 0.2–2.4 ppm using o-dianisidine). The procedures suffer few interferences.     

分光光度法测定豆类中铁的含量(Ⅱ)

豆类无污染,无农药残毒,营养丰富,具有特殊风味,并且很多豆类还有医疗保健作用.用分光光度法直接测定了豆类中铁的含量,方法简便快速准确,对指导人们合理食用豆类补铁及进一步开发豆类提供了可靠的理论依据.     

Kinetics of the oxidation of sulphite by tetrachloroaurate(III)

Summary The reaction between sulphite and gold(III) in hydrochloric acid medium has been studied; an initial complex is formed prior to electron transfer. The reaction rate is inversely proportional to the hydrogen ion concentration and the reaction appears to proceed through the intermediate formation of a free radical which reacts with gold(III) to give the products. Evidence for the formation of dithionate together with sulphate is presented.     

Synthesis of bis(pyrimidyl)furoxanes by the oxidation of bis(pyrimidyl)glyoximes

Conclusions This is the first report of the synthesis of a 3,4-bis(pyrimidyl)furoxane by the oxidation of bis (pyrimidyl)glyoxime. The substrate used was 1,2-bis(2,4-diethoxypyrimidin-6-yl) glyoxime.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 915–917, April, 1988.Deceased.     

The effect of molybdenum(VI) on the production of arsine by the tetrahydroborate(III) reaction

Molybdenum(VI) increases signals in the determination of arsenic after reduction by tetrahydroborate(III). An increase in the signal by up to two-and-a-half fold is observed when arsenic(III) is determined in the presence of sulphuric and hydrochloric acid concentrations of 0.01-0.02M. The enhancement effect disappears at higher acid concentrations and is eliminated by the presence of L-cysteine. Signals from other hydride-forming elements (antimony, bismuth and tin) were reduced in the presence of molybdenum(VI). Reduction of interferences in the hydride-forming reaction from nickel and cobalt is observed, so that the range of tolerance of these elements is extended by one and two orders of magnitude, respectively. The interference reducing effect is not as profound as that observed with L-cysteine.     

On the stabilization of niobium(V) solutions by zirconium(IV) and hafnium(IV)

Niobium cannot be separated from zirconium or hafnium when these elements occur together in solution with common anions such as chloride and sulphate. This is ascribed to the co-polymerization of niobium(V) and the hydrolysed ionic species of zirconium(IV) and hafnium(IV) to form colloidal particles. In hydrochloric acid the particles are positively charged, whereas in sulphate solution the Zr-and Hf-sulphate complexes confer a negative charge. The two cases are considered separately.     

Effect of the pH on the complexation of Cu(II), Ni(II) and Fe(III) Ions by a vine leaf litter extract by fluorescence quenching

An extract of dead vine leaves (vitis viniferal) (VLE) was obtained by the extraction procedure for fulvic acids and its interaction (at a concentration of 25mg/L in 0.1 M KNO₃) with the Cu(II), Ni(II) and Fe(III) ions was studied in the pH range between 3 and 6. This interaction was monitored by synchronous molecular fluorescence, since bands due to the fluorescent ligands undergo quenching upon complex formation. After the chemometric isolation of the quenching profiles from the raw spectra by a self-modeling mixture analysis, SIMPLISMA, they were analyzed by two methods: (i) graphical procedures based on the Stern-Volmer model; and (ii) a non-linear least-squares procedure. For the Cu(II) and Ni(II) ions, the treatment by these two methods provided similar values both for the logarithm of the conditional stability constants (log Kc) and the percentage of fluorescent structures that do not participate in the complexation. The log Kc were (standard deviations in parenthesis): Cu(II) ion, 2.4 (3), 3.37(3), 4.4(1) and 4.92(9), respectively, for pH = 3, 4, 5 and 6; Ni(II)ion, 2.9(1), 3.3(2), and 4.09(3), respectively, for pH = 4, 5 and 6. For Fe(III) an interaction with VLE was observed, but no values for Kc could be obtained.     

Oxidation induced by the antioxidant glutathione (GSH)

Remarkably efficient oxygen atom transfer from an intermediate of glutathione (GSH) autoxidation to an organometallic ruthenium arene thiolato complex is observed under physiologically-relevant conditions.     

Study of the kinetics of the oxidation of complexones by vanadium (V)

Conclusions The kinetics of the oxidation of ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid by vanadium(V) was studied; the reaction is first order with respect to V(V) and the complexone. The reaction rate constants were determined, and the activation energies of the oxidation processes were calculated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1212–1215, June, 1973.     

Synthesis of pyridine bases by the chichibabin method (review)

Published data on the synthesis of pyridine bases from carbonyl compounds or acetylene and ammonia by the Chichibabin method are summarized.slated from Khimiya Geterotsiklicheskilch Soedinenii, No. 2, pp. February, 1996.     

Light Promotes the Immobilization of U(VI) by Ferrihydrite

The environmental behaviors of uranium closely depend on its interaction with natural minerals. Ferrihydrite widely distributed in nature is considered as one main natural media that is able to change the geochemical behaviors of various elements. However, the semiconductor properties of ferrihydrite and its impacts on the environmental fate of elements are sometimes ignored. The present study systematically clarified the photocatalysis of U(VI) on ferrihydrite under anaerobic and aerobic conditions, respectively. Ferrihydrite showed excellent photoelectric response. Under anaerobic conditions, U(VI) was converted to U(IV) by light-irradiated ferrihydrite, in the form of UO_2+x (x < 0.25), where •O₂⁻ was the dominant reactive reductive species. At pH 5.0, ~50% of U(VI) was removed after light irradiation for 2 h, while 100% U(VI) was eliminated at pH 6.0. The presence of methanol accelerated the reduction of U(VI). Under aerobic conditions, the light illumination on ferrihydrite also led to an obvious but slower removal of U(VI). The removal of U(VI) increased from ~25% to 70% as the pH increased from 5.0 to 6.0. The generation of H₂O₂ under aerobic conditions led to the formation of UO₄•xH₂O precipitates on ferrihydrite. Therefore, it is proved that light irradiation on ferrihydrite significantly changed the species of U(VI) and promoted the removal of uranium both under anaerobic and aerobic conditions.     

Determination of traces of iron(II) in the presence of iron(III) by the bathophenanthroline method

Traces of iron(II) (1-30 ppM) in the presence of iron(III) were determined (error <10%) by the bathophenanthroline method. Interference of iron(III) was eliminated by masking with sodium pyrophosphate (2.5-60 mg). The iron(II) complex was extracted with n-butanol, at pH 4.2-4.7.     

Studies on the extraction of chromium(VI) by ketones

A study of the extraction of chromium(VI) from aqueous media by ketones was made. Extraction of chromium was found to be most efficient from aqueous hydrochloric acid solutions. A mechanism for the extraction of chromium(VI) from aqueous hydrochloric acid solutions by methyl isobutyl ketone is proposed involving the formation of a receptor in the organic phase, the exchange of the chloride ion of the receptor for the anionic chromium(VI) species of the aqueous phase, and the solvation of the extracted chromium species. The differences in the abilities of various ketones to extract chromium(VI) from aqueous hydrochloric acid solutions, and the differences in the extraction of chromium (VI) from various aqueous acids by methyl isobutyl ketone are attributed to the differences in the formation of receptors.     

Spectrophotometric determination of uranium(vi) by the azide reaction

Azide has been investigated as a spectrophotometric reagent for uranium(VI). The system is more sensitive than the thiocyanate reaction. It obeys Beer's law in the range 2–180 p.p.m. of uranium. The colour is sensitive to hydrogen ion concentration ; maximum absorbance and stability are attained at pH 5–5.5. Iron(III) interferes seriously, but can be masked by EDTA. Fe⁺², Cr⁺³, Ni⁺², Th⁺⁴, Cr₂O₇^-2, WO₄^-2, VO₃^- and F^- interfere. The deep yellow colour cannot be extracted with organic solvents. A mono-azido-uranium(Vl) ion is present in dilute solutions; its dissociation constant is 2.3 ±20.27·10^-3.     

Acceleration of the (4+2)-cycloreversion by the alkoxide substituent

The (4+2)-cycloreversion of the Alder-Rickert type is powerfully accelerated by the 1-alkoxide substituent.     

Dealkylation of alkylcobalt complexes by the mercury(II) electrophile

The dealkylation of a variety of RCo(BDMBg)⁺ complexes by Hg²⁺ is discussed. (The ligand BDMBg^- is formed by the condensation of two moles of 2,3-butanedionemonoxime with one mole of 1,3-propanediamine or 1,2-ethanediamine.) The products of the dealkylation reaction are Co^III(BDMBg)(H₂O)²⁺₂ and RHg⁺. All reactions are first order in the [Hg²⁺]. The second order rate constants (k₂) vary from 5.9 M^-1 sec^-1 (R = CH₃) to 5.7 x 10^-3M^-1 sec^-1 (R = n-C₃H₇). The relative rates for R are: CH₃ ? C₂H₅ τ C₆H₅CH₂ τ n-C₄H₉ ? n-C₃H₇. This order and other evidence are indicative of an S_E2 mechanism with an attack by Hg²⁺ on the carbon bonded to the cobalt.