Anion recognition by bisimidazolium and bisbenzimidazolium cholapods

Bile acid-based acyclic receptors bearing two imidazole and benzimidazole moieties have been synthesized. Anion binding studies using ¹H NMR revealed that imidazolium receptor exhibits high selectivity for chloride ion while benzimidazolium receptor showed selectivity for Y-shaped acetate ion through hydrogen bond interactions involving imidazolium C-2 and acetyl methylene hydrogens.     

Spectrophotometric determination of bismuth,cobalt, and nickel after extraction of their xanthates with molten naphthalene

Summary A new method for the spectrophotometric determination of bismuth, cobalt and nickel after extraction of their xanthates into molten naphthalene is described. The optimum pH values are 2.4–4.5 for Bi, 7.5–9.0 for Co, 5.5–7.5 for Ni. The naphthalene containing the metal chelates is dissolved in chloroform, and the absorbance is measured against a reagent blank at 362, 350 and 420 nm for Bi, Co and Ni and respectively. Few ions interfere and the method has been applied successfully for the determination of these metal ions in various complex materials.

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Zusammenfassung Eine neue Methode für die spektrophotometrische Bestimmung von Wismuth, Kobalt und Nickel nach Extraktion ihrer Xanthate mit geschmolzenem Naphthalin wurde beschrieben. Das optimale pH für Wismut beträgt 2,4–4,5, für Kobalt 7,5–9,0 und für Nickel 5,5–7,5. Das die Metallchelate enthaltende Naphthalin wird in Chloroform gelöst und die Extinktion gegen eine Reagens-Leerlösung bei 362, 350 bzw. 420 nm für Bi, Co bzw. Ni gemessen. Nur wenige Ionen stören. Das Verfahren wurde mit Erfolg zur Bestimmung der genannten Ionen in verschiedenen komplexen Gemischen angewandt.

     

NMR spectroscopic study of the inclusion complex of desloratadine with β-cyclodextrin in solution

Desloratadine (DES) is an antihistamine used in the treatment of allergies and chronic urticaria. ¹H NMR spectroscopic study of varying ratios of DES and β-Cyclodextrin (β-CD) in D₂O suggests the formation of a 1:1 inclusion complex formed by the penetration of Cl-substituted aromatic ring into the β-CD cavity. The stoichiometry and binding constant of the complex were determined by Scott’s method.     

Polarographische Untersuchungen von aus Cadmium(II) und Propylendiamin in wäßrigem Dimethylformamid entstandenen Komplexen

The reduction of Cd(II) in propylenediamine was found to be reversible and diffusion controlled. The complexes of Cd(II) with propylenediamine in 25%, 50%, and 75% dimethylformamide have been studied polarographically using theDeFord andHume's treatment as extended byIrving. Increase in the stability constants was observed with increase in dimethylformamide percentage. The percentage composition of the various complexed and uncomplexed species in 25% and 50% dimethylformamide are presented.     

Complexation of Fluvastatin Sodium with β-Cyclodextrin: NMR Spectroscopic Study in Solution

¹H NMR spectroscopic study of fluvastatin sodium (FLU), β-Cyclodextrin (β-CD) and their mixtures confirmed the formation of FLU/β-CD inclusion complex in solution. The stoichiometry of the complex was determined to be 1:1 and the overall binding constant (K _s) was calculated to be 340 M⁻¹. Two dimensional COSY, ROESY and DEPTO experiments were performed for the unambiguous assignment of aromatic proton resonances and it was found that two isomeric forms of FLU are present in solution. It was confirmed with the help of ROESY spectral data that only F-substituted aromatic ring penetrates the β-CD cavity and there is chiral differentiation by the β-CD as one of the isomer binds more strongly, which is indicated by the intensity of correlation peaks. The mode of penetration of the guest into the β-CD cavity was also established and structure of the complex has been proposed.     

Synthesis of 2- and 4-substituted 5,12-dihydroxy-6,11-dioxo-1-azanaphthacenes from 2-aminoquinizarine

The reaction of 2-aminoquinizarine with α,β-unsaturated carbonyl compounds in presence of 10N-hydrochloric acid gives 2- and 4-substituted 5,12-dihydroxy-6,11-dioxo-1-azanaphthacenes.     

Approximation for Certain Stancu Type Summation Integral Operator

In the present paper,we consider Stancu type generalization of the summation integral type operators discussed in [15].We apply hypergeometric series for obtaining moments of these operators.We also discuss about asymptotic formula and error estimation in terms of modules of continuity.     

Electronic,mechanical, phase transition,and thermo-physical properties of TMC (TM = V,Nb, and Ta): high pressure ab initio study

The structural, electronic, mechanical, phase transition, and thermo-physical properties of refractory carbides, viz. VC, NbC, and TaC have been computed in stable B1 and high pressure B2 phases by means of two different ab initio calculations using pseudo- and full-potential schemes. These materials have mixed covalent-, metallic-, and ionic-type bonding. The calculations of elastic constants show the mechanical stability of these materials in B1 phase only. The brittle nature and anisotropy is observed in these materials in B1 phase. Non-central forces are present in both the phases. Elastic wave velocities and Debye temperature have also been calculated. The present results on structural, phase transition, elastic, and other properties are in reasonably good agreement with the available experimental and theoretical data. The calculations in high pressure phase need experimental verification.     

Theoretical investigation of the alloxan–dialuric acid redox cycle

The redox cycle between alloxan, a mild oxidizing agent, and its reduction partner, dialuric acid, is investigated using density functional theory. It is found that the initial step is the one‐electron reduction of alloxan followed by protonation, yielding a stable neutral radical, AH^·. The radical can then accept another electron to form the dialuric acid anion. The formation of this anion is thermodynamically favored in both the gas phase and in solution. The radical may also undergo dimerization to alloxantin, followed by the transfer of a proton from one moiety to another, yielding alloxan and dialuric acid. This reduction is thermodynamically feasible in the gas phase, but not in aqueous solution. In the case of reduction of alloxan by glutathione at the physiological pH, computed redox potentials indicate that a two‐electron reduction is the favored course of reaction, yielding directly the dialuric acid anion, which then undergoes aerial oxidation to yield the superoxide radical. The redox cycling between alloxan and dialuric acid is responsible for the diabetogenic activity of alloxan, producing cytotoxic radicals on reoxidation of dialuric acid. © 2013 Wiley Periodicals, Inc.