Hydrogen-bonded mononuclear nickel(II) benzoate complexes: synthesis and structural studies

[Tp^Ph,MeNi(Cl)Pz^Ph,MeH] (1) has been synthesized by the reaction of hydrotris(3-phenyl-5-methyl-pyrazol-1-yl) borate [Tp^Ph,Me], NiCl₂ · 6H₂O and 3-phenyl-5-methyl-pyrazole [Pz^Ph,MeH]. The reaction of 1 with variously substituted sodium p–X–benzoates resulted in the formation of complexes of the type [Tp^Ph,MeNi(p–X–OBz)Pz^Ph,MeH] (X = H for 2, F for 3, Cl for 4, NO₂ for 5, Me for 6, OMe for 7, OH for 8, CHO for 9 and CN for 10). Single crystal X-ray studies suggest that all these complexes have a five-coordinate metal center and the benzoate groups are monodentate in a square pyramidal geometry. The X-ray studies also reveal that the uncoordinated oxygen atom of the benzoate forms intramolecular hydrogen-bonds with the NH group of the coordinated pyrazole. The substituents present on the benzoate ring are involved in different types of intermolecular interactions and the complexes exhibit different crystal packing. Complexes 2–10 were tested for superoxide dismutase activity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Comparative Studies on the Analytical and Antioxidant Activities of the Medicinally Important Stem Bark of Holoptelea integrifolia

JPC – Journal of Planar Chromatography – Modern TLC - Holoptelea integrifolia (Sanskrit: chirivilva, Hindi: chilbil, family: Ulmaceae) is a large deciduous tree, growing up to 18 m...     

Efficient and Rapid Synthesis of Highly Functionalized Novel Symmetric 1,4-Dihydropyridines Using Glacial Acetic Acid as Solvent

A new series of 1,4-dihydropyridines bearing a pyrazole moiety in the 4-position were synthesized by a variation of the classical Hantzsch synthesis. The reaction of 1,3-diphenyl-1H-pyrazole-4-carbaldehyde 4a–n with 3-amino crotononitrile in the presence of glacial acetic acid afforded novel 3,5-dicyano-2,6-dimethyl 1,4-dihydropyridines 5a–n. The procedure has short reaction time (15–20 min), easy workup, and good yield of product. The structures of all synthesized compounds were well characterized by mass, infrared, ¹H and ¹³C NMR, and elemental analysis.     

Structure and packing of aminoxyl and piperidinyl acrylamide monomers

The closely related title compounds, 4‐acrylamido‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl, C₁₂H₂₁N₂O₂, (I), and N‐(2,2,6,6‐tetramethylpiperidin‐4‐yl)acrylamide monohydrate, C₁₂H₂₂N₂O·H₂O, (II), are important monomers in the preparation of redox‐active polymers. They comprise an acrylamide group of the usual s‐cis configuration appended to a 2,2,6,6‐tetramethyl‐substituted piperidine‐1‐oxyl radical or a piperidinyl chair, respectively. The adjacent amide and piperidinyl H atoms are approximately trans across the C—N bond. The packing in (I) is dominated by N—H...O hydrogen bonds; these are supported by C—H...O contacts to form an R₂¹(6) ring repeat, a motif which has been observed in other acrylamide structures. In (II), hydrogen bonds are again key to the packing arrangements. In this case, the incorporated solvent water molecule acts as an acceptor through its O atom and as a donor through both H atoms, binding three adjacent piperidinylacrylamide molecules into layers. In both structures, weak C—H...O contacts involving the piperidinyl methyl H atoms and a proximal acrylamide carbonyl O atom extend the structure in the third dimension.     

Energy transfer from Sm3+ to Er3+ in zinc phosphate glass

A study of energy transfer from samarium to erbium ions in zinc phosphate glass has been performed for a range of donor (1.0 wt% fixed) and acceptor concentrations ranging from 0.2 wt% to 1.2 wt%. The intensity of emission spectra of Sm³⁺ ions in the presence of Er³⁺ ions shows an overall decrease, thereby suggesting a non radiative energy transfer from Sm³⁺ ions to Er³⁺ ions. The interaction mechanism between the donor and acceptor ions is found to be mainly electric dipole-dipole in nature. The parameters required for the quantitative study of energy transfer e.g. energy transfer efficiencies, transfer probabilities, critical transfer distances have been computed.     

Facile one‐pot synthesis of linear and radial block copolymers of styrene and isoprene through a novel coupling agent by living anionic polymerization

A new methodology is successfully used for the concurrent synthesis of three different copolymers; diblock, triblock, and three‐armed star‐block copolymers of styrene and isoprene via the living anionic polymerization with control over the molecular weight and weight fractions of each block. The room temperature polymerization process has resulted in the well defined linear and radial block copolymers, when the living di‐block of poly(styrene‐b‐isoprene) was coupled using cheap and readily available malonyl chloride as a novel coupling agent giving nearly 100% yield. The resulting block copolymers have narrow polydispersity index (PDI = 1.01–1.09) with a good agreement between the calculated and the observed molecular weights. The results are further supported by fractionation of the block copolymers by reversed‐phase temperature gradient interaction chromatography (RP‐TGIC) technique followed by size exclusion chromatography (SEC). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2636–2641, 2010     

Determination of Heavy Metals in Lichens Growing on Different Ecological Habitats in Schirmacher Oasis,East Antarctica

Twelve lichen species growing on different ecological habitats in East Antarctica were analyzed for Cr, Cu, Fe, Pb and Zn. All the species had consistently higher amounts of Fe and Cu, as their substrata were iron and copper mineralized rocks. the foliose and fruticose lichens had a greater concentration of heavy metals than the crustose ones. Significantly, lead was not detected in any sample indicating that the area is still free from pollution.