Optical and photocatalytic properties of single crystalline ZnO at the air-liquid interface by an aminolytic reaction

Crystalline flowerlike ZnO was synthesized by an aminolytic reaction at the air-liquid interface in an aqueous media at an alkaline pH. A thin visible film was formed at the air-liquid interface by self-assembly of flowerlike ZnO. Diffraction studies show rearrangement of the single crystalline units at the air-liquid interface leading to the formation of nanobelts. These nanobelts overlap systematically to form petals of the flowerlike structure; individual petals get curved with time. Each nanobelt is found to be single crystalline and can be indexed as the hexagonal ZnO phase. The organic product formed in the aminolytic reaction and dissolution-reprecipitation mechanism is the driving force for the formation of flowerlike ZnO at the air-liquid interface. A clear relationship between the surface, photocatalytic, and photoluminescent properties of ZnO is observed. The flowerlike structure exhibits a blue shift (3.56 eV) in the band emission as compared to bulk ZnO (3.37 eV). The photodegradation of methylene blue over the flowerlike ZnO catalyst formed at the air-liquid interface and in the sediments shows enhanced photocatalytic activity. The sub-bands formed due to surface defects facilitate separation of charge carriers increasing their lifetime, leading to enhanced photocatalytic activity of flowerlike ZnO.     

Synthesis,structural studies and some biological aspects,including nematicidal and insecticidal properties,of organotin(IV) complexes formed with biologically active sulfonamide imine ligand

The synthetic, spectroscopic and biological studies of some organotin(IV) complexes derived from sulfonamide imine having a nitrogen–nitrogen donor system have been undertaken. The sulfonamide imine, on interaction with organotin(IV) chlorides, yields complexes having an Sn←N bond. The structures of these compounds have been elucidated by microestimations and spectral (UV, IR, ¹H, ¹³C and ¹¹⁹Sn NMR) studies, which unerringly point to the trigonal bipyramidal and octahedral geometries for the unimolar and bimolar reactions respectively around tin(IV), as the active lone pair of nitrogen is also included in the coordination sphere. Studies were conducted to assess the comparative growth‐inhibiting potential of the synthesized complexes against the sulfonamide imine for a variety of fungal and bacterial strains. The studies demonstrate that the concentrations reached levels sufficient to inhibit and kill the pathogens. The results of the biological studies have also been compared with the conventional standards, Bavistin and Streptomycin, taken for antifungal and antibacterial activities respectively. The complexes also show higher nematicidal and insecticidal properties. Copyright © 2004 John Wiley & Sons, Ltd.     

Mechanics of binding of a single integration-host-factor protein to DNA

We report on a single-molecule experiment where we directly observe local bending of a 76 base pair DNA oligomer caused by specific binding of a single integration-host-factor (IHF) protein. The conformational change of the DNA is detected by optically monitoring the displacement of a micron size bead tethered to a surface by the DNA. Since in the bound state the DNA loops around the IHF, a mechanical tension on the DNA tends to eject the protein. We measure how the rate for the protein to fall off the DNA depends on the mechanical tension in the DNA, gaining insight into the energy landscape for this molecular bond. Our method further demonstrates a new paradigm of molecular detection, where ligand binding is detected through the conformational change induced in the probe molecule. Here this allows the detection of single, unlabeled proteins.     

NEMATICIDAL,INSECTICIDAL, ANTIFERTILITY,ANTIFUNGAL AND ANTIBACTERIAL ACTIVITIES OF SALICYLANILIDE SULPHATHIAZOLE AND ITS MANGANESE,SILICON AND TIN COMPLEXES

A facile synthesis and studies on the stereochemistry and biochemical aspects of some organosilicon(IV), organotin(IV), and manganese(II) complexes derived from imine having N^∪N^∪O donor system is reported. The imine was prepared by the condensation of salicylanilide with sulphathiazole. This imine reacts with organosilicon(IV)chloride, organotin(IV)chloride, and hydrated manganese(II) chloride to yield compounds having M─O and M←N bonds. The structures of the compounds have been elucidated by physicochemical and spectral (IR, ¹H NMR, ¹³C NMR, ²⁹Si NMR, ¹¹⁹Sn NMR, and ESR) studies, which clearly point to a trigonal bipyramidal geometry around silicon(IV) and tin(IV), and tetrahedral geometry around manganese(II), as the active lone pair of the nitrogen is also included in the coordination sphere. In the search for better fungicides and bactericides, studies were conducted to assess the growth-inhibiting potential of the synthesized complexes against various pathogenic fungal and bacterial strains. These complexes are highly active against nematode (Meloidogyneincognita) and insect (Trogodermagranarium). The activity will be increased with increasing concentration. These studies demonstrate that the concentrations reached levels that are sufficient to inhibit and kill the pathogens. All compounds have also been found to act as sterilizing agents by reducing the production of sperm in male mice.     

Toxicological and pesticidal studies on novel bioactive sulfonamide imine organotin(IV) complexes

Toxicological, pesticidal and stereochemical aspects of organotin(IV) complexes with a sulfonamide imine ligand having an N^∩N donor system are described with the support of elemental analysis, IR, UV, ¹H NMR, ¹³C NMR and ¹¹⁹Sn NMR spectroscopy. The spectral data suggest that the ligand acts in a monobasic bidentate manner coordinating through the nitrogen atom. The complexes have been characterized on the basis of molecular weight determinations, conductivity measurements, and magnetic measurements. The isolated products are coloured solids, soluble in dimethylsulfoxide, dimethylformamide (DMF) and methanol. All the complexes are monomeric in nature, as indicated by their molecular weight determinations. Conductivity measurements in dry DMF show them to be non‐electrolytes. From the analyses of these studies the donor sites of the ligand are located and the geometries of the donor environment around the tin(IV) acceptor centres proposed. The ligand and its metal complexes are tested in vitro against a number of pathogenic fungal and bacterial strains and the findings are discussed. Emphasis has been given to the nematicidal properties. Copyright © 2003 John Wiley & Sons, Ltd.     

Room temperature ferromagnetism in undoped and Fe doped ZnO nanorods: Microwave-assisted synthesis

One-dimensional (1D) undoped and Fe doped ZnO nanorods of average length ∼1 μm and diameter ∼50 nm have been obtained using a microwave-assisted synthesis. The magnetization (M) and coercivity (H_c) value obtained for undoped ZnO nanorods at room temperature is ∼5×10⁻³ emu/g and ∼150 Oe, respectively. The Fe doped ZnO samples show significant changes in M -H loop with increasing doping concentration. Both undoped and Fe doped ZnO nanorods exhibit a Curie transition temperature (T_c) above 390 K. Electron spin resonance and Mössbauer spectra indicate the presence of ferric ions. The origin of ferromagnetism in undoped ZnO nanorods is attributed to localized electron spin moments resulting from surface defects/vacancies, where as in Fe doped samples is explained by F center exchange mechanism.     

Facile, chemoenzymatic synthesis of the potent antiviral compound, 2-acetonylinosine

A facile and efficient methodology for the chemoenzymatic synthesis of the antiviral compound, 2-acetonylinosine has been developed. The present synthetic strategy, which has generality, is a dramatic improvement on the methodologies currently available for the synthesis of functionalized purine nucleosides of therapeutic interest.     

Microwave‐assisted synthesis and insecticidal properties of biologically potent organosilicon(IV) compounds of a sulfonamide imine

Microwave‐assisted synthesis and spectroscopic studies of dimethyl‐, diphenyl‐ and triphenyl‐silicon(IV) chelates derived from the reactions of organochlorosilanes with the sodium salt of a biologically active nitrogen donor ligand N^∩NH are described. The resulting products have been isolated and characterized by elemental analyses, molecular weight determinations and conductance measurements. On the basis of electronic, infrared, ¹H, ¹³C and ²⁹Si NMR spectral studies, trigonal bipyramidal and octahedral geometries have been suggested for the resulting complexes. The biological activity of the ligand and its corresponding complexes has been examined with regard to antifungal and antibacterial activity against pathogenic fungi and bacteria, and the results are quite encouraging. All the compounds have also been found to act as nematicides and insecticides, by reducing the number of nematodes (Meloidogyne incognita) and insects (Trogoderma granarium). Copyright © 2005 John Wiley & Sons, Ltd.