Donor properties of the nitrone function in copper(II) complexes of some 2-hydroxy-1-naphthylnitrones

Summary Copper(II) complexes of the type CuL₂, 2H₂O and CuL₂. Py where L=-(2-hydroxy-1-naphthyl)-N-R-nitrone (R= methyl, phenyl and variously substituted phenyls) have been isolated and characterised. They have normal magnetic moments. Their ligand field spectra indicate an octahedral geometry for the dihydrates and a five-coordinate environment for the pyridine adducts. Increased (C=N) and considerably decreased (N-O) frequencies in these complexes reveal the presence of - and -interactions of the ligand with copper through nitrone oxygen. The effect of pyridine adduct formation is to increase the Cu-O -interaction.     

Normal co-ordinates through coriolis coupling constants

Normal co-ordinates, force fields and isotopic frequencies have been calculated for someXY ₃ andXY ₄-type molecules using coriolis coupling constants.     

3′-Hydroxy-4-methoxychalcone as a potential antibacterial coating on polymeric biomaterials

Antimicrobial property of chalcone coated high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP) and polyurethane (PU) against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa is reported here. The presence of chalcone on the surface was confirmed from fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Bacterial adhesion decreased considerably on all the coated surfaces. Bacterial adhesion was highest on PU surface (most hydrophobic) and lowest on HDPE (most hydrophilic) surface. Chalcone seems to damage the membrane of the bacteria as well as exhibit slimicidal activity. Reasonably good correlation was observed between the CFU (Colony Forming Units) ratio (it is defined as the ratio of CFU on coated surface to the chalcone uncoated surface) at the 24th hour against both hydrophobicity of the microorganism and roughness of the coated polymeric surfaces. Increasing roughness of the polymer and hydrophobicity of the microorganisms were positively and negatively correlated respectively with CFU ratio. Hence, the chalcone coated polymers can be used in the development of newer biomaterials.     

Uniform Convergence Analysis of Finite Difference Scheme for Singularly Perturbed Delay Differential Equation on an Adaptively Generated Grid

<正>Adaptive grid methods are established as valuable computational technique in approximating effectively the solutions of problems with boundary or interior layers. In this paper,we present the analysis of an upwind scheme for singularly perturbed differential-difference equation on a grid which is formed by equidistributing arc-length monitor function.It is shown that the discrete solution obtained converges uniformly with respect to the perturbation parameter.Numerical experiments illustrate in practice the result of convergence proved theoretically.     

Synthesis of 4H-chromenes by silver(Ⅰ)-catalyzed cycloaddition of ortho-quinone methides with N-allenamides

Chromenes represent an important class of six-membered heterocycles and have drawn tremendous attention in recent years. In this article, we report a convenient and practical synthesis of this heterocycle by a silver(I)-catalyzed cycloaddition reaction between in situ generated ortho-quinone methides and N-allenamides. Diverse 4H-chromenes were synthesized in good to excellent yields under very mild conditions.     

Thermal radiation and surface roughness effects on the thermo-magneto-hydrodynamic stability of alumina–copper oxide hybrid nanofluids utilizing the generalized Buongiorno’s nanofluid model

Journal of Thermal Analysis and Calorimetry - Sequel to the fact that hybrid nanofluidic systems (e.g. scalable micro-/nanofluidic device) exhibit greater thermal resistance with increasing...     

Stability-indicating RP-HPLC method development and validation for determination of nine impurities in apixaban tablet dosage forms. Robustness study by quality by design approach

A quality by design (QbD) based high-resolution HPLC method is described for determination of impurities in apixaban (APX) in the tablet dosage form. Employing a simple and stability-indicating HPLC method, nine known impurities were quantified with good peak resolution. Mobile phase A (MP-A) was prepared with buffer and acetonitrile 90:10 v/v, while mobile phase B (MP-B) contained water and acetonitrile 10:90 v/v. The gradient program was 0 min, MP-A 75%, B 25%; 20 min, MP-A 65%, B 35%; 30 min, MP-A 40%, B 60%; 40min, MP-A 40%, B 60%; 42 min, MP-A 75%, B 25%; and 50 min, MP-A 75%, B 25%. The chromatographic separation was achieved using a Zorbax RX C₁₈ 250 × 4.6 mm column, 5 μm (1.0 ml min⁻¹, 280 nm, 50 μl) and a column temperature of 40°C. Several separation studies were carried out using design of experiments to optimize the method. Validation results confirm the applicability of the developed method for quality analysis and stability studies of the regular product on the manufacturing stream.     

Enantioseparation of DPP-4 Inhibitors on Immobilized Crown Ether-Based Chiral Stationary Phase

A group of DPP-4 inhibitors such as alogliptin, linagliptin and saxagliptin were selected for enantioseparation for this study. Crown ether columns contain a chiral crown ether ring as a chiral selector is suitable for the compounds having primary amino groups. Since the selected compounds contain free amino groups, a crown ether column was selected for enantiomeric separation of dipeptidyl peptidase-4 inhibitors. Dipeptidyl peptidase-4 inhibitors are a class of oral hypoglycemics that block dipeptidyl peptidase-4 enzyme and can be used to treat diabetes mellitus type 2. A sensitive HPLC method was developed to separate the enantiomers of each dipeptidyl peptidase-4 inhibitor. Effects of various parameters such as type of solvents, selection of additives, effect of pH and column temperature on chromatographic results were studied. The optimal conditions for the chiral separation of dipeptidyl peptidase-4 inhibitors without any derivatization were investigated.     

Kinetics and mechanism of oxidation of N,α-diphenylnitrones by 4-(dimethylamino)pyridinium chlorochromate (DMAPCC) in aqueous DMF medium

The kinetics of oxidation of aldonitrones by 4-(dimethylamino)pyridinium chlorochromate (DMAPCC) has been studied in aqueous N,N-dimethylformamide in the presence of perchloric acid. The reaction follows first-order kinetics with respect to each of DMAPCC and nitrone. The order with respect to [H⁺] was found to be close to zero. The rate of oxidation was unaltered by the variation of [NaClO₄] but addition of MnSO₄ decreased the rate. The reaction rate was found to decrease with a decrease in dielectric constant of the medium. Electron-releasing and electron-withdrawing groups perturb the reaction rate with a good Hammett correlation. The oxidation products were found to be benzaldehyde and nitrosobenzene. The reaction was carried out at four different temperatures and the activation parameters have been calculated. On the basis of the experimental findings, a suitable mechanism has been proposed.     

Synthesis of Diverse Oxa‐Carbocycle‐Annulated Flavones Using the Combined Claisen Rearrangement and Ring‐Closing Metathesis

A simple and efficient route for the synthesis of oxepine‐, oxocine‐, oxepinone‐, and dioxocine‐angularly annulated flavone skeletons has been developed. The combined Claisen rearrangement and the ring‐closing metathesis are used as key steps for the construction of C₇/C₈–C₆–C₆ tricyclic core structures.