Structure of interfacial water on fluorapatite (100) surface

The structure relaxation mechanism of the fluorapatite (100) surface under completely hydrated ambient conditions has been investigated with the grazing incidence X-ray diffraction (GIXRD) technique. Detailed information on lateral as well as perpendicular ordering corresponding to the water molecules and atomic relaxations of the (100) surface of fluorapatite (FAp) crystal was obtained from the experimental analysis of the CTR intensities. Two laterally ordered water layers are present at the water/mineral interface. The first layer consists of four water molecules located at 1.6(1) A above the relaxed fluorapatite (100) surface while the second shows the presence of only two water molecules at a distance of 3.18(10) A from the mineral surface. Thus, the first layer water molecules complete the truncated coordination sites of the topmost surface Ca atoms, while the second water layer molecules remain bonded by means of H-bonding to the first layer molecules and the surface phosphate groups. Molecular mechanics simulations using force field techniques are in good agreement with this general structural behavior determined from the experiment.     

Synthesis and biological activity of phosphorylated compounds of 2‐substituted benzazoles

A series of organophosphorus derivatives have been synthesized by the reaction of phosphorylchloride with 2‐(2′‐hydroxyphenyl)benzimidazole and 2‐(2′‐hydroxynaphthyl)benzimidazole in the presence of KHCO₃ in dry THF in different molar ratios. Newly synthesized derivatives were tested for their insecticidal activity against Periplenata americana. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:246–249, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20533     

SnIV Porphyrin Scaffolds for Axially Bonded Multiporphyrin Arrays: Synthesis and Structure Elucidation by NMR Studies

A simple, one‐step, supramolecular strategy was adopted to synthesize Sn^IV‐porphyrin‐based axially bonded triads and higher oligomers by using meso‐pyridyl Sn^IV porphyrin, meso‐hydroxyphenyl‐21,23‐dithiaporphyrin, and Ru^II porphyrin as building blocks and employing complementary and non‐interfering Sn^IV?O and Ru^II ??? N interactions. The multiporphyrin arrays are stable and robust and were purified by column chromatography. ¹H, ¹H–¹H COSY and NOESY NMR spectroscopic studies were used to unequivocally deduce the molecular structures of Sn^IV‐porphyrin‐based triads and higher oligomers. Absorption and electrochemical studies indicated weak interaction among the different porphyrin units in triads and higher oligomers, in support of the supramolecular nature of the arrays. Steady‐state fluorescence studies on triads indicated the possibility of energy transfer in the singlet state from the basal Sn^IV porphyrin to the axial 21,23‐dithiaporphyrin. However, the higher oligomers were weakly fluorescent due to the presence of heavy Ru^II porphyrin unit(s), which quench the fluorescence of the Sn^IV porphyrin and 21,23‐dithiaporphyrin units.     

Bleach Enhancement of Mixed Wood Pulp by Xylanase–Laccase Concoction Derived Through Co-culture Strategy

Mixed enzyme preparation having both xylanase and laccase activity was evaluated for its bleach enhancing ability of mixed wood pulp. The enzyme was produced through co-cultivation of mutant Penicillium oxalicum SAU_E-3.510 and Pleurotus ostreatus MTCC 1804 under solid-state fermentation. Bleaching of pulp with mixed enzyme had resulted into a notable decrease in kappa number and increased brightness as compared to xylanase alone. Analysis of bleaching conditions had denoted that 8 IU g⁻¹ of mixed enzyme preparation (xylanase/laccase, 22:1) had led into maximal removal of lignin from pulp when bleaching was performed at 10% pulp consistency (55 °C, pH 9.0) for 3 h. An overall improvement of 21%, 8%, 3%, and 5% respectively in kappa number, brightness, yellowness, and viscosity of pulp was achieved under derived bleaching conditions. Process of enzymatic bleaching was further ascertained by analyzing the changes occurring in polysaccharide and lignin by HPLC and FTIR. The UV absorption spectrum of the compounds released during enzymatic treatment had denoted a characteristic peak at 280 nm, indicating the presence of lignin in released coloring matter. The changes in fiber morphology following enzymatic delignification were studied by scanning electron microscopy.     

Multiporphyrin arrays on cyclophosphazene scaffolds: synthesis and studies

The stable and robust cyclotriphosphazene and cyclotetraphosphazene rings were used as scaffolds to prepare hexa- and octaporphyrin arrays by treating N(3)P(3)Cl(6) and N(4)P(4)Cl(8), respectively, with 5-(4-hydroxyphenyl)-10,15,20-tri(p-tolyl)porphyrin (N(4) core) or with its thiaporphyrin analogues (N(3)S and N(2)S(2) cores) in THF in the presence of Cs(2)CO(3) under simple reaction conditions. Thiaporphyrins were examined in addition to the normal porphyrin to tune the electronic properties of the resultant arrays. Observation of the molecular ion peaks in the mass spectra confirmed the molecular structures of the arrays. 1D and 2D NMR techniques were employed to characterize the multiporphyrin arrays in detail. The (1)H NMR spectra of the multiporphyrin arrays each show a systematic set of signals, indicating that the porphyrin units are arranged in a symmetrical fashion around the cyclophosphazene rings. All signals in the (1)H NMR spectra were assigned with the aid of COSY and NOESY experiments. The protons of each porphyrin unit are subject to upfield and downfield shifts because of the ring-current effects of neighboring porphyrin units. Optical, electrochemical, and fluorescence studies of the arrays indicated that the porphyrin units retain their independent ground- and excited-state characteristics. Cu(II) and Ni(II) derivatives of hexaporphyrin and octaporphyrin arrays containing N(4) porphyrin units and N(3)S porphyrin units were synthesized, and complete metalation of the arrays was confirmed by their mass spectra and by detailed NMR characterization of the Ni(II) derivatives of hexa- and octaporphyrin arrays containing N(4) porphyrin units. Electrochemical studies indicated that Cu(II) and Ni(II) ions present in the thiaporphyrin units of the arrays can be stabilized in the +1 oxidation state, which is not possible with arrays containing normal porphyrin units.     

Working group report: Heavy-ion physics and quark-gluon plasma

This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported.     

Direct Esterification of Aromatic Aldehydes with Tetraphenylphosphonium Bromide under Oxidative N‐Heterocyclic Carbene Catalysis

An unconventional reagent, tetraphenylphosphonium bromide, was employed as a phenyl source in the direct transformation of aromatic aldehydes to the corresponding phenyl esters under oxidative N‐heterocyclic carbene (NHC) catalysis. The phenyl esters were obtained in moderate yields under mild and organocatalytic conditions.