Redox and oxo-abstraction Reactions of Silylamine with MoOCl4

Trimethylsilyldiethylamine Me₃SiNEt₂ and MoOCl₄ (1:1) undergo a free radical redox reaction in CH₂Cl₂ or Et₂O to form MoCl₃O(HNEt₂). Reduction occurs even in aprotic media like CCl₄ and CS₂ to give Mo^V complexes Mo₂Cl₆O₂(N₂Et₄) and Mo₂Cl₆O₂[(SCNEt₂)₂S₂], respectively. A 2:1 reaction in nonionizing protic solvents undergoes redox cum cleavage to provide MoCl₂O(NEt₂) (HNEt₂) but a reaction at reflux temperature in 1,2-dichloroethane leads to diethylammonium salt, [Et₂NH₂][MoCl₄O(HNEt₂)]. Higher molar reactions (3:1, 4:1) in CH₂Cl₂ or Et₂O are associated with redox reaction as well as oxygen atom abstraction to form de-oxo Mo^IV complex MoCl₃(NEt₂)(HNEt₂)₂, whereas, a 3:1 reaction in CS₂ forms Mo₂Cl₄O(S₂CNEt₂)₄. Compounds have been characterized by elemental analyses, redox titration, magnetic moment, conductance, infrared, electronic absorption and ¹H-NMR measurements.     

Extraction behavior of uranium(VI), plutonium(IV), zirconium(IV), ruthenium(III) and europium(III) with γ-pre-irradiated solutions of N,N′-methylbutyl substituted amides in n-dodecane

The extraction of plutonium(IV), uranium(VI), zirconium(IV), europium(III) and ruthenium(III) with -pre-irradiated n-dodecane solutions of methylbutyl substituted hexanamide (MBHA), octanamide (MBOA) and decanamide (MBDA) from 3.5M HNO₃ has been studied as a function of absorbed dose up to 184×10⁴ Gray. The distribution ratios (K_d) of uranium(VI) decreased gradually up to a dose of 50×10⁴ Gray and became almost constant thereafter, while ruthenium(III) and europium(III) were not extracted in the entire dose range studied. The K_d values of Pu(IV) decreased gradually up to 10×10⁴ Gray, for MBOA, and 30×10⁴ Gray for MBHA and MBDA and then increased up to a dose of 72×10⁴ Gray, indicating the synergistic effect of radiolytic products at higher doses. The extraction of zirconium(IV) was found to increase gradually up to 72×10⁴ Gray. However, the steep fall in K_d values of plutonium(IV), zirconium(IV) beyond a dose of 72×10⁴ Gray was atrributed to third phase formation. The radiolytic degradation of amides was monitored by quantitative IR spectroscopy and was found to follow the order MBOA>MBDA>MBHA at 184×10⁴ Gray having the amines and carboxylic acids as the main radiolytic products.     

Effect of reaction media on the growth and photoluminescence of colloidal CdSe nanocrystals

Using cadium oxide (CdO) as the Cd precursor and tri-n-octylphosphine selenide (TOPSe) as the Se source, TOP-capped and TOP/tri-n-octylphosphine oxide (TOPO)-capped CdSe nanocrystals were synthesized without the use of an acid. The synthetic approach involved the addition of a TOPSe/TOP solution into a CdO/TOP solution with or without TOPO at one temperature and subsequent growth at a lower temperature. The temporal evolution of the optical properties, namely, absorption and luminescence, of the growing nanocrystals was monitored in detail. A comprehensive examination on the control of the photoluminescence (PL) properties was performed by systematically varying the TOP/TOPO weight ratio of the reaction media. Surprisingly, a rational choice of 100% TOP or 80% TOP was found to produce "quality" nanocrystals when monitored under the present experimental conditions and growth-time scale. The term "quality" is mainly based on the sharp features and rich substructure exhibited in the absorption spectra of the growing nanocrystals, as well as the sharp features in the emission spectra with narrow full width at half-maximum (fwhm). There are two distinguishable stages of growth: an early stage (<5 min) and a later stage. TOP plays a major role in the control of a slow growth rate in the early stage, while TOPO controls slow growth in the later stage. The optical sensitivity of the growing nanocrystals when dispersed in nonpolar or polar solvents was studied, including two size-dependent parameters, namely, the solvent sensitivity (PL intensity) and nonresonant Stokes shift (NRSS). The insights gained from the present study enable a synthetic approach in which high-quality CdSe nanocrystals are achieved with high synthetic reproducibility.     

Polymer electrolytes based on room temperature ionic liquid: 2,3-dimethyl-1-octylimidazolium triflate

Room temperature ionic liquid (DMOImTf) based upon 2,3-dimethyl-1-octylimidazolium cation and trifluoromethanesulfonate or triflate (CF(3)SO(3))(-) anion has been synthesized and shows conductivity of 5.68 mS/cm and viscosity of 26.4 cP at 25 degrees C. Ion conducting polymer electrolytes based on polymers (poly(ethylene oxide) (PEO) and polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP)) and ionic liquid (DMOImTf) were prepared in film form by the casting technique. The conductivity of polymer electrolytes containing 0.5 M LiCF(3)SO(3) in PEO:DMOImTf taken in equal weight ratio increases with the addition of propylene carbonate (PC) while its mechanical stability improved by dispersing nanosize fumed silica. However, polymer electrolytes containing PVdF-HFP and ionic liquid show a high value of conductivity (10(-4)-10(-3) S/cm) alongwith better mechanical stability.     

Influence of Urbach Energy,Temperature, and Longitudinal Position in the Active Layer on Carrier Diffusion Length in Perovskite Solar Cells

The diffusion length of charge carriers in the active layer of a perovskite solar cell (PSC) of the structure Glass/PEDOT: PSS/CH₃NH₃PbI₃/PC60BM/Al is modelled. It is found that the diffusion length depends on the position x in the active layer measured from the PEDOT: PSS interface, Urbach energy and temperature. By varying the voltage in the range from zero to , it is shown that the dependence of diffusion length on the position x in the active layer reduces at higher voltage. The combined influence of applied voltage and temperature on the diffusion length of charge carriers is investigated and it is found that in the low voltage range the diffusion length is temperature independent, but it becomes significantly temperature dependent at higher voltages. Also, it is found that the diffusion length decreases as the applied voltage increases and this reduction becomes much more significant at higher voltage and temperatures. The combined influence of applied voltage and Urbach energy on diffusion length of charge carriers reveals that the diffusion length decreases when both the applied voltage and Urbach energy increase. However, the reduction in the diffusion length due to the increase in Urbach energy becomes less significant at higher voltage.     

Tetrachloroferrate(III)-selective liquid membrane electrode based on crystal violet

An extract of crystal violet-tetrachloroferrate(III) in nitrobenzene was used to prepare a tetrachloroferrate(III)-selective liquid membrane electrode with a poly(vinyl chloride) support. The optimal conditions to determine 2.5 × 10^–5 – 5.0 × 10^–2 M iron(III) as tetrachloroferrate(III) (anionic slope 56 mV/decade, detection limit 7.9 × 10^–6 M) were found to be 4.0–5.5.M total chloride in 0.75–1.5M hydrochloric acid. The electrode was reliably applied to determine iron in human blood, haematite and mineralized vitamin syrup by direct potentiometry, standard and sample additions as well as standard subtraction techniques.     

Selective Spectrophotometric Determination of Copper in Milk with Phenanthraquinone Monothiosemicarbazone

The red complex formed by copper (II) and phenanthraquinone monothiosemicarbazone has an absorption maximum at 530 nm with a molar absorptivity of 14000 cm^?1 mole^?1. The pH range for the determination is 1.1–6.6. Optimum range of concentration for accurate determination is 0.50–3.47 ppm of copper (II) in 50% methanol medium. The limits of interference due to foreign ions have been studied. The method has been successfully employed for the determination of copper in various samples of milk.     

Potentiometric studies in oxidation-reduction reactions: Oxidation with chloramine-b. indirect determinations

Chloramine-B has been used as an oxidising agent to determine indirectly potassium iodate, potassium metaperiodate, potassium, bromate, potassium dichromate, hydrogen peroxide, chloramine-T and potassium permanganate by a potentiometric method. An excess of potassium iodide added to each of the substances in an acid medium is titrated back with a standard solution of chloramine-B, using platinum foil as an oxidation-reduction electrode coupled with a saturated calomel electrode through an agar-agar potassium chloride bridge.     

o-hydroxylmethylphenylchalcogens: synthesis, intramolecular nonbonded chalcogen...OH interactions, and glutathione peroxidase-like activity

[Structure: see text]. The synthesis and characterization of a series of organochalcogen (Se, Te) compounds derived from benzyl alcohol 13 are described. The synthesis of the key precursor dichalcogenides 15, 22, and 29 was achieved by the ortho-lithiation route. Selenide 18 was obtained by the reaction of the dilithiated derivative 14 with Se(dtc)2. Oxidation of 15 and 22 with H2O2 afforded the corresponding cyclic ester derivatives 17 and 24, respectively. Oxidation of selenide 18 with H2O2 affords the spirocyclic compound 19. The presence of intramolecular interactions in dichalcogenides 15 and 22 has been proven by single-crystal X-ray studies. The cyclic compounds 17 and 19 have also been characterized by single-crystal X-ray studies. GP(X)-like antioxidant activity of selenium compounds has been evaluated by the coupled bioassay method. Density functional theory calculations at the mPW1PW91 level on ditelluride 22 have identified a fairly strong nonbonding interaction between the hydroxy oxygen and tellurium atom. The second-order perturbation energy obtained through NBO analysis conveys the involvement of n(O) --> sigma(Te-Te) orbital overlap in nonbonding interaction. Post wave function analysis with the Atoms in Molecules (AIM) method identified distinct bond critical point in 15 and 22 and also indicated that the nonbonding interaction is predominantly covalent. Comparison between diselenide 15 and ditelluride 22 using the extent of orbital interaction as well as the value of electron density at the bond critical points unequivocally established that a ditelluride could be a better acceptor in nonbonding interaction, when the hydroxy group acts as the donor.     

Thermodynamics of molecular interactions in ethyl iodide+toluene mixtures

The excess Gibb's free energy of mixing, G^E, for ethyl iodide+toluene at 25°C have been obtained from the measured vapor pressuure data. The H^E and G^E values for ethyl iodide+toluene are positive throughout the ethyl iodide concentration range and G^E>H^E. The results have been analyzed in terms of Flory and ideal associated model theory of nonelectrolyte solutions. It has been observed that the ideal associated model approach which assumes the presence of AN and A₂B molecular species describes well (within±10 J-mol^–1 in the worst case) the general dependence of H^E on X_A (mole fraction of ethyl iodide) over the whole composition range for ethyl iodide+toluene mixtures. The equilibrium constants for A+A AB and 2A+BA₂B reactions along with the enthalpies of formation of AB and A₂B molecular species have been calculated.