Push-Pull Butadienes: Evidence for a possible C?H…︁S hydrogen bond in 4-(methylthio)-4-nitro-1-(pyrrolidin-1-yl)buta-1,3-diene

X-Ray crystal structure of 4-(methylthio)-4-nitro-1-(pyrrolidin-1-yl)buta-1,3-diene ( 2b )

1 The C-atoms of the butadiene chain have been numbered as shown in 1 and 2 . These numbers have been retained throughout the discussion for the sake of clarity and consistency.

indicates the presence of a C? H…?S hydrogen bond. This might also explain the observed downfield shift of this proton in solution.     

Rapid quenchofluorimetric determination of nickel(II) in some real and environmental samples

A fluorimetric method for rapid determination of Ni at trace and ultratrace levels [1 ng/ml- 1 g/ml] has been developed. It is based on the efficient quenching action of Ni (II) on the native fluoresence [_ex(max) = 288 nm, _em(max) = 444.8 nm] of 4,7-diphenyl 1,10-phenanthrolinedisulfonate (bathophenanthrolinedisulfonate) solution at low acidities. The method is very simple, rapid and accurate with high precision (R.S.D. = 0.66% at 50 ng/ml). The method has been applied directly to mineralised solutions of several real and environmental samples and the results of nickel determinations are in excellent agreement with the certified values. It is a quick single-step method that requires no clean-up.     

Optimal tests for no contamination in symmetric multivariate normal mixtures

SenGupta and Pal (1991,J. Statist. Plann. Inference,29, 145–155) have recently obtained the locally optimal test for zero intraclass correlation coefficient in symmetric multivariate normal mixtures, with known mixing proportion, for the case when the common mean,m, and the common variance, ², are known. Here, we establish that even under the general situation, when some or none ofm and ² are known, simple optimal tests can be derived, which are locally most powerful similar, whose exact cut-off points are already available and which retain all the previous optimality properties, e.g. unbiasedness, monotonicity and consistency. Some power tables are presented to demonstrate the favorable performances of these tests.     

Analysis by gas chromatography-mass spectrometry of the essential oils from the aerial parts of Rutheopsis herbanica (Bolle) Hans. & Kunk., gathered in Fuerteventura (Canary Islands)

The essential oil from the aerial parts of Rutheopsis herbanica (Bolle) Hans. & Kunk., growing in Fuerteventura, Canary Islands, Spain, was studied by gas chromatography and gas chromatography-mass spectrometry, and 42 constituents were identified. The major components were found to be alpha-pinene (29.4%), dillapiole (21.3%), limonene (14.1%), beta-pinene (13.2%) and myristicin (10.0%). As far as we know, this is the first report on the essential oil composition of this species.     

Triazene-N-oxides as new type of fluorimetric reagents. part i. trace determination of zirconium at the nanogram level

Summary Triazene-N-oxides are being reported for the first time as a new type of metallofluorescers. Among eleven triazene-N-oxides studied, 3-(2-hydroxyphenyl)-l-phenyl triazene-N-oxide(R₁₁) gives fluorescence with Zr, Hf, Nb(V) and Ta(V). A method has been developed for trace determination of Zr with R₁₁, excitation and emission maxima of the system being 435 nm and 570 nm respectively.In the pH range between 1.65 and 1.95 the fluorescence intensity of Zr-R₁₁ system is linear over the range 5 ppb to 1.5 ppm of zirconium. Some thirty ions show no interference or can be removed by the use of masking agents. Only Hf, W and Mo cause interference. The method is simple and very rapid.

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Triazen-N-Oxide als neuartige fluorimetrische Reagenzien. I. Bestimmung von Zirkon im Nanogrammbereich

Zusammenfassung Triazen-N-oxide wurden erstmalig als fluoreszenzanregende Reagenzien für Metalle vorgeschlagen. 3-(2-Hydroxyphenyl)-1-phenyltriazen-N-oxid (R₁₁) gibt mit Zr, Hf, Nb(V) and Ta(V) Fluoreszenz. Ein Verfahren für die Bestimmung von Zr-Spuren mit R₁₁ durch Anregung bei 435 nm und Messung beim Fluoreszenz-Maximum (570 nm) wurde ausgearbeitet. Im pH-Bereich 1,65–1,95 ist die Fluoreszenz-Intensität von Zr-R₁₁ zwischen 5 ppb und 1,5 ppm Zr linear. Einige dreißig Ionen stören nicht bzw. können maskiert werden. Nur Hf, Mo und W stören.

     

Oxidative Cleavage of S–S Bond During the Reduction of Tris(pyridine‐2‐carboxylato)manganese(III) by Dithionite in Sodium Picolinate–Picolinic Acid Buffer Medium

The reduction of tris(pyridine‐2‐carboxylato)manganese(III) by dithionite has been investigated within the temperature window 288–303 K and at pH range 5.22–6.10 in sodium picolinate–picolinic acid buffer medium. The reaction obeys the following stoichiometry: The reaction is described in terms of a mechanism that involves an initial complex formation between S₂O₄^2? and [Mn^III(C₅H₄NCO₂)₃] followed by S–S bond cleavage to give 2HSO₃^? and [Mn^II(C₅H₄NCO₂)₂(H₂O)₂] as the products via the formation of SO₂^●? radical anion. Kinetics and spectrophotometric evidences are cited in favor of the suggested mechanism. Thermodynamic parameters associated with the equilibrium step and the activation parameters with the rate‐determining step have been computed.     

Bulk heterojunction solar cells based on self-assembling disc-shaped liquid crystalline material

In this article, effect of addition of disc-shaped liquid crystalline material, namely 2, 3, 6, 7, 10, 11-hexabutyloxytriphenylene, in poly (3-hexylthiophene): [6, 6]-phenyl-C61-butyric acid methyl ester containing bulk heterojunction (BHJ) solar cells has been investigated. These disc-shaped molecules organise into ordered columnar hexagonal structures through intermolecular π ? π interactions as monitored by polarised light optical microscopy. Current–voltage characteristics of the device prepared with liquid crystal layer exhibited a short-circuit current of 10.5 mA cm^?2 and a fill factor of 35%. The resultant power conversion efficiency (PCE) was 1.54%. The influence of varying the thickness of liquid crystal layer and annealing on these solar cells was also studied. The short circuit current and PCE of 12.9 mA cm^?2 and 2.3% was achieved for these BHJ solar cells containing self-organised discotic liquid crystals in the active layer under one sun condition after annealing.     

Enhanced Adsorption of Hexavalent Chromium onto Magnetic Calcium Ferrite Nanoparticles: Kinetic,Isotherm, and Neural Network Modeling

Calcium ferrite nanoparticles with super-paramagnetic behavior were synthesized via simple chemical precipitation method for effective removal of hexavalent chromium from aqueous media. The properties of synthesized nanoparticles were studied by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET), and vibrating sample magnetometer (VSM) measurements. The ferrite nanoparticles have shown polycrystalline nature and high BET specific surface area (229.83 m²/g) with active functional groups on the surface. The adsorption process follows second-order kinetics with the involvement of intra-particle diffusion and adsorption capacity as much as 124.11 mg/g was determined from the Langmuir isotherm. The thermodynamic analysis revealed that the adsorption process was feasible, spontaneous, and exothermic in nature. A three-layer feed-forward back-propagation artificial neural network (ANN) model was employed to predict the removal (%) of Cr(VI) ions as output. Optimal ANN network (4:8:1) shows the minimum mean squared error (MSE) of 0.00161 and maximum coefficient of determination (R²) of 0.984. The adsorption process is mostly influenced by solution pH and followed by adsorbent dosage, initial Cr(VI) concentration, and contact time as illustrated by sensitivity analysis. With small size and high surface area, biocompatibility, ecofriendly nature, easy magnetic separation, and enhanced adsorption capacity towards Cr(VI), calcium ferrite nanoparticles will find its potential application in wastewater remediation.     

Synthesis of Novel Drug‐Like Small Molecules Based on Quinoxaline Containing Amino Substitution at C‐2

A series of novel “drug‐like” small molecules based on quinoxaline containing amino substitution at C‐2 were synthesized. All these molecules were prepared either via the reaction of 2‐phenyl‐3‐(piperazin‐1‐yl)quinoxaline with acyl bromides or benzyl bromides or various carboxylic acids or via the reaction of 2‐chloro‐3‐phenylquinoxaline with various amines. The structures of these novel compounds were confirmed by spectral analysis. The strategy used is simple and efficient and afforded good yields of quinoxaline derivatives.