Biological aspects of Schiff base–metal complexes derived from benzaldehydes: an overview

Schiff bases are stable imines containing C=N, where N is bonded to an alkyl or aryl group, but not with hydrogen and are prepared by condensation of aliphatic or aromatic primary amine with carbonyl compounds. They have the general formula R₁R₂C?=?NR₃, where R₃?≠?H. The presence of the basic donor N atom and the stability of the imine function render Schiff bases as the most favored ligands that have the ability to stabilize metal ions in different oxidation states. The chelating environment in a Schiff base profoundly influences the electron distribution in the coordination sphere of metal in a complex and thereby regulates the property of the compounds in a big way. The structural diversity in some of the metal complexes with multidentate Schiff base ligands has triggered a wide range of applications of this class of compounds in sensors, catalysis, biology, medicines, and photonics. This review compiles the synthesis and biological activities (antimicrobial, antioxidant, anticancer, antitubercular, DNA interaction studies) of benzaldehyde-based Schiff bases and their metal complexes.     

XNBR/LDH nanocomposites: Effect of vulcanization and organic modifier on nanofiller dispersion and strain‐induced crystallization

In elastomer/organo clay nanocomposites, the morphological characteristics, and hence the mechanical properties, of the vulcanizates are strongly influenced by the organic modifier and the vulcanization process. When the elastomer itself undergoes strain‐induced crystallization, both the organic modifier and the dispersed filler particles could significantly influence the crystallization process. These phenomena are very common in case of natural rubber‐based vulcanizates. In this study, the similar effects have been demonstrated with carboxylated nitrile rubber (XNBR) and organically modified layered double hydroxide (O‐LDH)‐based nanocomposites. The effect of size of the organic modifier was obviously visible on the interlayer distance of O‐LDH and also on the morphological reorganization of the dispersed O‐LDH particles during vulcanization process. The strain‐induced crystallization of the XNBR was found to be strongly dependent on the morphological change that occurs during vulcanization process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Generation of Bianchi type V cosmological models with varying Λ-term

Bianchi type V perfect fluid cosmological models are investigated with cosmological term varying with time. Using a generation technique (Camci et al., 2001), it is shown that Einsteins field equations are solvable for any arbitrary cosmic scale function. Solutions for particular forms of cosmic scale functions are also obtained. The cosmological constant is found to be a decreasing function of time, which is supported by results from recent type Ia supernovae observations. Some physical aspects of the models are also discussed.     

On existence of undominated pure strategy Nash equilibria in anonymous nonatomic games: a generalization

In this paper, we generalize the exitence result for pure strategy Nash equilibria in anonymous nonatomic games. By working directly on integrals of pure strategies, we also generalize, for the same class of games, the existence result for undominated pure strategy Nash equilibria even though, in general, the set of pure strategy Nash equilibria may fail to be weakly compact. Received August 2001     

Ferrocene-based anion receptor bearing amide and triazolium donor groups

A novel ferrocene-based anion receptor bearing amide and triazolium donor groups and its anion complexation have been reported. We found that it shows marked electrochemical selectivity to F(-), followed by AcO(-) > Cl(-) > Br(-) > I(-), which is in accordance with (1)H NMR titration results.     

A modified method for the determination of uranium in Nb/Ta minerals by LED fluorimetry

A modified LED fluorimetry determination of uranium in Nb/Ta minerals has been developed. The mineral is brought into solution by fusion with mixed phosphate flux (NaH₂PO₄, H₂O and Na₂HPO₄). Iron quenches uranium fluorescence when it is present above the ratio of (iron to uranium) 100. Uranium is separated in ethyl acetate by solvent extraction and then stripped back into pyrophosphate buffer (pH ~ 7) prior to its LED fluorimetry determination. This modified method has been applied for the determination of uranium in synthetic mixtures and Nb/Ta minerals including Certified Reference Materials (X1807) with high degree of accuracy and precision.

     

Domain pattern in ferroelectric triglycine sulphate using pyroelectric effect

A method to study domain structure in ferroelectrics, using pyroelectric effect is described. Variation of pyroelectric signal from the surface of a triglycine sulphate crystal plate has been studied by scanning the surface of the crystal with a low wattage He-Ne laser beam. The integrated pyroelectric signal is due to two components, namely, (1) the primary component arising out of the change in spontaneous polarization with temperature and (2) the delayed component arising out of the possible polarization reversal. The component of an electric field along the ferroelectric axis due to thermal hemisphere within the crystal plate formed by the laser beam has been calculated and shown to exceed coercive field, making polarization reversal possible. The delayed pyroelectric signal is a measure of polarization reversal within the patch illuminated and its observed variation over the surface yields information of the domain structure.     

Modulated Binary–Ternary Dual Semiconductor Heterostructures

A generic modular synthetic strategy for the fabrication of a series of binary‐ternary group II‐VI and group I‐III‐VI coupled semiconductor nano‐heterostructures is reported. Using Ag₂Se nanocrystals first as a catalyst and then as sacrificial seeds, four dual semiconductor heterostructures were designed with similar shapes: CdSe‐AgInSe₂, CdSe‐AgGaSe₂, ZnSe‐AgInSe₂, and ZnSe‐AgGaSe₂. Among these, dispersive type‐II heterostructures are further explored for photocatalytic hydrogen evolution from water and these are observed to be superior catalysts than the binary or ternary semi‐conductors. Details of the chemistry of this modular synthesis have been studied and the photophysical processes involved in catalysis are investigated.     

Selective oxoammonium salt oxidations of alcohols to aldehydes and aldehydes to carboxylic acids

The oxidation of alcohols to aldehydes using stoichiometric 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (1) in CH(2)Cl(2) at room temperature is a highly selective process favoring reaction at the carbinol center best able to accommodate a positive charge. The oxidation of aldehydes to carboxylic acids by 1 in wet acetonitrile is also selective; the rate of the process correlates with the concentration of aldehyde hydrate. A convenient and high yield method for oxidation of alcohols directly to carboxylic acids has been developed.