Diaminodithioether complexes of nickel(II) and palladium(II): A unique case of dealkylation of S,S′-thioether

Summary Nickel(II) and palladium(II) complexes of the 1,3-di(o-aminophenylthio) propane (H₂L¹) and 1,2-di(o-aminophenylthio)xylene (H₂L²) ligands have been prepared and characterized. The hydrobromide salt of H₂L¹ gave a 12 ligand-metal complex of Pd^II, whereas free H₂L¹ formed the usual 1:1 species. The reaction of Na₂PdCl₄ with H₂L² resulted in S,S-dealkylation of the ligand and formation of a mononuclear complex of the corresponding thiol, i.e. 2-aminobenzenethiol. NiCl₂, NiBr₂ and Ni(ClO₄)₂ did not react directly with H₂L². Ni^II is a fairly hard ion and therefore does not coordinate to the soft thioether moiety in H₂L² in the absence of soft anions which symbiotically motivate Ni^II to act as a soft acceptor. It thus does not react with H₂L² in the presence of hard ions such as Cl^–, Br^- and ClO ₄ ^– , but, the in situ reaction of the constituents produced the tetrahedral Ni^II complex, contrary to earlier reports of similar types of octahedral species.     

Spectrophotometric and potentiometric studies of oxovanadium(IV) chelates with Eriochrome black T and Solochrome black 6 BN

Vanadium(IV) forms colored chelates with Erio T and Solo 6 BN (λ_max 570 and 580 nm, respectively) at pH 3.8. The composition MR₂ of the chelates investigated was established by continuous variation, mole ratio, slope ratio and straight-line methods spectrophotometrically. For photometric determination of V(IV) with these reagents Sandell's sensitivity, Beer's law range, Ringbom optimum range were also determined. Bjerrum and Calvin potentiometric titration technique was employed to determine the stepwise formation constants of each system. For V(IV)-Erio T system values of log K₁ = 14.4, log K₂ = 10.9 and for V(IV)-Solo 6 BN system log K₁ = 16.1, log K₂ = 11.8 were obtained.     

Non-aqueous cerimetric determination of thioureas

Ammonium hexanitratocerate (in acetonitrile) solution has been used as an oxidimetric reagent for the visual and potentiometric determination of thiourea and its alkyl derivatives in acetonitrile medium. The thioureas are oxidized to their corresponding disulphides. The method is simple, accurate, reliable and widely applicable.     

Iodometric microdetermination of carboxyl function by indirect and direct procedures

Two iodometric procedures have been described for the microdetermination of certain organic acids which can be adopted for evaluating 0.03–0.1 meq of these acids. These methods consist of treating the acid sample with an excess of neutral potassium iodide and iodate. In the indirect method the iodate used up is measured whereas the direct procedure is based on the titration of the liberated iodine. The latter procedure has been applied to determine acids in a water-alcohol medium also. The effect of various factors influencing the stoichiometry of the reactions involved has also been studied.     

Synthesis, characterization, photoluminescence and EPR investigations of Mn doped MgAl2O4 phosphors

MgAl₂O₄:Mn phosphors have been prepared at 500 °C by combustion route. Powder X-ray diffraction (XRD) indicated the presence of mono-MgAl₂O₄ phase. Scanning electron microscopy showed that the powder particle crystallites are mostly angular. Fourier transform infrared spectroscopy confirmed the presence of AlO₆ group which makes up the MgAl₂O₄ spinel. Photoluminescence studies showed green/red emission indicating that two independent luminescence channels in this phosphor. The green emission at 518 nm is due to ⁴T₁ → ⁶A₁ transition of Mn²⁺ ions. The emission at 650 nm is due to the charge-transfer deexcitation associated with the Mn ion. EPR spectrum exhibits allowed and forbidden hyperfine structure at g=2.003. The g≈2.00 is due to Mn²⁺ ion in an environment close to tetrahedral symmetry. It is observed that N and χ increase with decrease of temperature obeying the Boltzmann law. The variation of zero-field splitting parameter (D) with temperature is evaluated and discussed.     

Suppressed ion chromatography for monitoring chemical impurities in steam for geothermal power plants

A suppressed ion chromatography (IC) technique has been evaluated as a chemical monitoring tool for detecting major anions (F-, Cl-, NO3- and SO4(2-)) of condensed steam in geothermal power plants. It is shown that the suppressed IC technique provides a suitable means for preventing possible damage to generating equipment in the geothermal industry. An electrical conductivity detector (0.1 microS sensitivity) with an anion-exchange column (IonPac AS4A-SC), a micro-membrane suppressor (AMMS II), and an isocratic high-pressure pump system were successfully used for detecting low concentrations of inorganic anions. Method detection limits for the anions of interest were <0.184 mg/L. Details of the IC methodology as well as some experimental results obtained during its application for the chemical monitoring of geothermal steam pipes are also described.     

Determination of nitrite and mixtures of bromide and iodide with o-iodosobenzoate

Nitrite diazotizes sulphanilamide, which then does not undergo 3,5-dibromination. Nitrite can therefore be determined by reaction with excess of sulphanilamide, the surplus of which is then titrated with o-iodosobenzoate or chloramine-T in the presence of potassium bromide, with Methyl Red as indicator. Mixtures of iodide and bromide can be analysed by oxidation of the iodide with excess of o-iodosobenzoate at pH 4-6, followed by extraction of the iodine (which is then titrated with thiosulphate) and then oxidation of the bromide in dilute sulphuric acid medium in the presence of sulphanilamide as bromine scavenger, the residual oxidant being evaluated iodometrically.     

A new route to obtain shape-controlled gold nanoparticles from Au(III)-beta-diketonates

Ligands with a beta-diketone skeleton have been employed for the first time as reductant to produce ligand stabilized gold nanoparticles of different shapes from aqueous HAuCl(4) solution. Evolution of stable gold nanoparticles follows first order (k approximately equal to 10(-2) min(-1)) kinetics with respect to Au(0) concentration. Growth of particles of different shapes (spherical or triangular or hexagonal) goes hand in hand under the influence of different beta-diketones, which have excellent capping and reducing properties. Chlorine insertion was observed to take place in the beta-diketone skeleton.     

Determination of 1,3-benzodioxanes in Piper mullesua by high-performance thin-layer chromatography

A new, simple, precise, and rapid high-performance thin-layer chromatographic method was developed for the determination of 6 benzodioxanes in Piper mullesua extract: 1',3'-benzodioxole-5'-(2,4,8-triene-isobutyl nonanoate), 1',3'-benzodioxole-5'-(2,4,12-triene-isobutyl tridecanoate), fargesin, sesamin, asarinin, 1',3'-benzodioxole-5'-(2,4,8-triene-methyl nonanoate). The ingredients were separated on a precoated Silica Gel 60 F254 plate with a solvent system of toluene-acetone (92 + 8). The 6 benzodioxanes were well separated and easily identified in this chromatographic system. The separated benzodioxanes were visualized by color development with a spray reagent consisting of 1 g vanillin dissolved in 100 mL H2SO4-ethanol (5 + 95, v/v). Quantitation was performed by scanning the spots and comparing the integrated areas of compounds in samples with those of standards. Recoveries from samples spiked with known amounts of the benzodioxanes were excellent. The results were comparable with those estimated by liquid chromatography.