Amberlite IR-120 catalysed efficient synthesis of glycosyl enamines and their application

β-Keto esters and acetyl acetone on condensation with glycosylated amino esters in the presence of IR-120 resin resulted in high yields of glycosyl enamino esters or ketones. The latter on cyclisation with NaH in toluene at reflux gave 6-glycosyl-5,6-dihydro-1H-pyridin-4-ones in fair to good yields.     

Sensitive and selective methods for determination of antipsychotic drug olanzapine in pharmaceuticals

Two simple and sensitive spectrophotometric methods have been developed for analysis of the antipsychotic drug olanzapine in pharmaceuticals. Method A is based on liberation of iodine by reaction between the drug and potassium iodate, followed by reaction with leuco crystal violet (LCV), the color of oxidized LCV being measured at 598 nm. Method B is based on oxidation of olanzapine with chloramine-T (CAT) in acidic medium, the unconsumed CAT being determined with rhodamine B, measuring the absorbance at 550 nm. Calibration graphs were linear over the ranges of 0.05–2.0 and 0.1–1.6 μg mL^?1 olanzapine for method A and B, respectively. The molar absorptivity, Sandell’s sensitivity, detection limit, and quantitation limit were found to be 1.59 × 10⁵, 0.00132, 0.038, and 0.117, respectively, for method A and 0.953 × 10⁵, 0.00221, 0.064, and 0.192, respectively, for method B. The optimum conditions and other analytical parameters were evaluated. The proposed methods have been applied successfully for analysis of olanzapine in pure form and its dosage forms, and no interference was observed from common excipients present in pharmaceutical formulations.     

Spectrophotometric analysis of trichloroethylene in various environmental and biological samples

A simple sensitive extractive spectrophotometric method for determination of trichloroethylene is proposed. Trichloroethylene is treated with pyridine to form glutaconic aldehyde by heterolytic cleavage of the pyridine ring. Glutaconic aldehyde is further coupled with 4-aminoacetanilide to form an orange–red dye which is extractable in 3-methyl-1-butanol. The extracted dye shows absorption maximum at 520 nm. The system obeys Beer’s law in the range of 0.05–0.8 μg mL^?1. Important analytical parameters such as time, temperature, reagent concentration, acidity etc. have been optimized for complete colour reaction. Sandell’s sensitivity and molar absorptivity for the system were found to be 0.001 μg cm^?2 and 1.2 × 10⁵ L mol^?1 cm^?1, respectively. The proposed method is satisfactorily applied to micro-level determination of trichloroethylene in various environmental and biological samples.     

Cooperative Effect of Noncovalent Interactions on Tetrel Bonding in Halogenated Silanes

Tetrel bond, a weak noncovalent interaction between the σ-hole of a Group IV element (silicon in our case) and the cloud of an electronegative element (oxygen in our case) is the focus of this work. The percentage strengthening of tetrel bond has been investigated by optimizing 16 binary complexes of halogenated silane and water of general formula SiX_nH_4−n−H₂O and 16 ternary complexes, of general formula NaX−SiX_nH_4−n−H₂O, where X=F, Cl, Br and I and n=1, 2, 3 and 4 at various levels of theory defined within the formalism of density functional theory (DFT). With the addition of NaX, tetrel bond between Si and O in SiX_nH_4−n−H₂O gets strengthened up to 49 %, owing to cooperativity effect exerted by hydrogen bonding between X and H in the ternary complex NaX−SiX_nH_4−n−H₂O. In the series of complexes studied here, overall stabilization due to cooperativity lies between 10 kJ/mol to 170 kJ/mol. This large extent of reinforcement due to cooperativity has never been showcased before. The exceptional stabilization and reinforcement owe its genesis to the transformation of the ternary complex into a cluster orchestrated by the H-bonding in most of the cases and covalent bonding in few of the cases.     

Laser‐Induced Self‐Assembled Nanostructures on Electron‐Transparent Substrates

Currently, one of the challenges in high‐resolution transmission electron microscopy (TEM) studies of nanomaterials is to make contamination‐free materials in a simple and time‐efficient way. Here, a method is demonstrated that combines nanosecond‐pulsed laser dewetting of thin films with a film float‐off technique to realize nanostructures (NSs) on electron‐transparent substrates in a robust and rapid manner. NSs of metal (Ag) and bimetals (AgCo, AuCo) ranging from 20 to 150 nm are synthesized on thin carbon film deposited on mica substrates. The NS/carbon system is subsequently transferred onto TEM grids by a float‐off process resulting from debonding of the carbon from mica due to their contrasting hydrophobic nature. This process enables the fabrication of different NSs on flexible and electron‐transparent substrates.     

Electroanalytical studies of complexes of tetracyclines with Cd(II), Pb(II) and Cu(II) in aqueous medium

The dissociation constants of protonated tetracycline, chlorotetracycline and desmethylchlorotetracycline and the overall stability constants of the complexes of Cd, Pb and Cu(II) with these tetracyclines have been determined.     

Magnetic interactions of iron nanoparticles in arrays and dilute dispersions

The magnetic properties of monodisperse Fe nanoparticles with over 4 orders of magnitude difference in concentration are studied by a combination of ordinary and remanent hysteresis loops, zero field cooled magnetization as a function of temperature, and magnetic relaxation rates. We compare the behavior of dilute dispersions with different concentrations, dispersions, and arrays made from the same particles, and nanoparticle arrays with different particle sizes and separations. The results are related to theoretical predictions and are used to create a unified picture of magnetostatic interactions within the assemblies.     

A study of mercury(II)-catalysed substitution of cyanide in hexacyanoferrate(II) by 2-methylpyrazine: effects of inhibitor on the catalysed reaction

The kinetics and mechanism of the mercury(II)-catalysed ligand substitution reaction between potassium hexacyanoferrate(II) and 2-methylpyrazine (2-Mepz), in potassium hydrogen phthalate buffer of pH 3.50 ± 0.02 at 25.0 ± 0.1 °C and constant ionic strength of 0.1 M, were studied spectrophotometrically by measuring the absorbance of the yellow-coloured product at 447 nm (λ_max). The reaction was studied under pseudo-first-order conditions using excess of 2-Mepz. The reaction was found to obey first-order dependence in concentration of both [Fe(CN)₆]⁴⁻ and 2-Mepz. At higher concentrations of 2-Mepz, the effect of [2-Mepz] levels off. A complex behaviour is observed on varying [Hg²⁺]. The effect of pH on the reaction rate was also analysed. The effects of dielectric constant and water content of the reaction medium have been interpreted in terms of the formation of a polar activated complex and suggest an I_d mechanism. The inhibitory effect of 2,3-dimercaptopropanol on the reaction was also studied and explained in terms of binding of this species to the catalyst.     

An eco-safe approach to benzopyranopyrimidines and 4H-chromenes in ionic liquid at room temperature

An environmentally benign, ionic liquid promoted multicomponent protocol to benzopyrano(2,3-d)pyrimidines and 4H-chromenes has been developed at room temperature. Results of the reaction depend on the nature of the nucleophile used in the reaction. Secondary amines result in the formation of benzopyrano(2,3-d)pyrimidines, whereas thiols give rise to 4H-chromenes under the same set of reaction conditions.     

Raman Spectroscopic Analysis of Perovskite-Structured Alkali Metal Fluorides Containing Nickel and Copper Ions

ABSTRACT

The mixed metal fluorides containing alkali metals have a range of important applications in optical and electronic devices. Raman spectrums of two such fluorides were examined. Raman spectrum of KCuF₃ at 300 K exhibited bands at 261, 295, 363, 468, 519, and 549 cm^?1, indicating site symmetry (orthorhombic) lower than the tetragonal symmetry as observed from the powder X-ray diffraction pattern. Cubic KNiF₃ showed bands at 410, 468, and 657 cm^?1. The first two bands were attributed to the second-order phonon scattering, and the band at 657 cm^?1 was assigned to two-magnon peak.