Positron interactions with overlayers of oxygen on GaAs(100)

The positron work-function, re-emission yield, and positronium fraction of an n-doped GaAs(100) surface were measured as a function of oxygen exposure. The energy distribution of positrons observed to be re-emitted indicated that the clean and oxygen exposed n-doped GaAs(100) surfaces had negative positron work-functions. The fraction of incident positrons re-emitted as bare positrons, (Y), was found to increase and the fraction re-emitted as positronium, (f_Ps), to decrease with increasing oxygen exposure. This suggests that surface modified GaAs may be useful as a contact material in the fabrication of GaAs based FAMs.     

Turkish perlite supported nickel oxide as the heterogeneous acid catalyst for a series of Claisen–Schmidt condensation reactions

Potentially active and eco-friendly solid acid catalysts have been synthesized by loading different weight percentages (10, 15, and 50) of nickel oxide on thermally activated Turkish perlite through the deposition-precipitation method. Structural features of prepared catalysts were analyzed using BET surface area analysis, X-ray diffraction, scanning electron microscope (SEM), SEM-EDX, transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR), pyridine adsorbed FT-IR, UV-Vis diffuse reflectance spectroscopy (DRS), and thermogravimetric analysis (TGA) techniques. Pyridine adsorbed FT-IR analysis confirmed the presence of the optimum amount of Bronsted acidic sites in a catalyst having 15 wt. % loading of nickel oxide, which was tested for catalyzing a series of Claisen–Schmidt condensation of cyclohexanone and aromatic aldehydes to produce good isolated yield (90%–93%) of 2,6-bis(substituted benzylidene)cyclohexanones, significantly used in anti-tumor and cytotoxic activities. The high catalytic efficiency of the chosen catalyst remains almost intact up to six reaction cycles. On higher wt. % loading of nickel oxide, crystallite size increases along with agglomeration of larger nickel oxide particles on catalyst surface resulting in pore blockage and poor catalytic activity. Loading of NiO on the surface of thermally activated Turkish perlite was confirmed by SEM-EDX analysis, and TEM observations show that the particle size of the preferred catalyst was less than 50 nm. Based on results drawn from XRD, FT-IR, pyridine adsorbed FT-IR, UV-Vis DRS studies, model structures were proposed for Turkish perlite and all prepared catalysts. During this work, the catalytic potential of the preferred catalyst was compared with other previously reported catalysts, and it showed appreciable results. The formed products were further confirmed by their melting point and ¹H-NMR analysis.     

Hydro­gen‐bond networks in tris(4‐hydroxy­phenyl)­methane and its 1:1 molecular complex with 4,4′‐bi­pyridine

In tris(4‐hydroxy­phenyl)­methane (or 4,4′,4′′‐methane­triyl­tri­phenol), C₁₉H₁₆O₃, mol­ecules are connected by O—H⃛O hydrogen bonds [O⃛O = 2.662 (2) and 2.648 (2) Å] into two‐dimensional square networks that are twofold interpenetrated. In tris(4‐hydroxy­phenyl)­methane–4,4′‐bi­pyridine (1/1), C₁₉H₁₆O₃·C₁₀H₈N₂, trisphenol mol­ecules form rectangular networks via O—H⃛O [O⃛O = 2.694 (3) Å] and C—H⃛O [C⃛O = 3.384 (3) Å] hydrogen bonds. Bi­pyridine mol­ecules hydrogen bonded to phenol moieties [O⃛N = 2.622 (3) and 2.764 (3) Å] fill the voids to complete the structure.     

A study of pyrazolo-benzimidazole derivatives as spleen tyrosine kinase inhibitors: an in-silico approach

Structural Chemistry - In an effort to contribute designing of improved anticancer molecules, in-silico prediction data including pharmacophore hypothesis, 3D-QSAR model, and molecular docking...     

Crystal Engineering: An Outlook for the Future

Crystal Engineering has traditionally dealt with molecular crystals. It is the understanding of intermolecular interactions in the context of crystal packing and in the utilization of such understanding in the design of new solids with desired physical and chemical properties. We outline here five areas which come under the umbrella of Crystal Engineering and where we feel that a proper planning of research efforts could lead to higher dividends for science together with greater returns for humankind. We touch on themes and domains where science funding and translation efforts could be directed in the current climate of a society that increasingly expects applications and utility products from science and technology. The five topics are: 1) pharmaceutical solids; 2) industrial solid state reactions; 3) mechanical properties with practical applications; 4) MOFs and COFs framework solids; 5) new materials for solar energy harvesting and advanced polymers.     

An improved and robust scale-up process aided with identification and control of critical process impurities in darunavir ethanolate

Research on Chemical Intermediates - A robust and safe industrial process, including five isolations and drying steps for widely prescribed anti-HIV (protease inhibitor) drug darunavir ethanolate...     

A new form of MgTa2O6 obtained by the molten salt method

Using molten salt route (with NaCl/KCl as the salt) we have been able to synthesize a new form of magnesium tantalate at 850°C. Powder X-ray diffraction data could be inde_xed on an orthorhombic unit cell with lattice parameters, ‘a’ = 15.36(1) ?, ‘b’ = 13.38(1) ? and ‘c’ = 12.10(1) ?. High resolution transmission electron microscopy and electron diffraction studies confirm the results obtained by X-ray studies. Energy dispersive X-ray spectroscopy helps ascertain the composition of MgTa₂O₆. The title compound shows a dielectric constant of ∼24 with a low dielectric loss of 0.006 at 100 kHz at room temperature. Dielectric constant is nearly unchanged with rise in temperature while the loss shows a very marginal increase (0.007 at 300°C). Dedicated to Prof J Gopalakrishnan on his 62nd birthday.     

Synthesis,spectroscopic characterization,and crystal structure of a novel indoline derivative

A new indoline derivative, tert-butyl 2′-amino-3′-cyano-6′-methyl-2-oxospiro[indoline-3,4′-pyran]-5′-carboxylate is eco-friendly synthesized, and its spectral properties and X-ray crystal structure are studied. In the molecule, the oxindole and pyran moieties are perpendicular to each other. The crystal structure is stabilized by intermolecular N?H···O and intramolecular C?H···O hydrogen bonds. Centrosymmetric dimer units are formed by intermolecular N?H···O hydrogen bonds. In addition, one C?H···π interaction is also observed.     

The Even/Odd Disparity in Organic Compounds

There are more organic compounds with an even number of carbon atoms than with an odd number. This disparity could result mainly from the methods used in synthetic chemistry to build large molecules from smaller ones. Samples of C₂₈, C₄₇ and C₄₈ compounds have been examined in this context.