Synthesis and characterization of new lead(II) complexes of Schiff bases derived from amino acids

Some new lead(II) complexes of the general formula Pb(L)₂, where HL = Schiff bases derived from the condensation of isatin and chloroisatin with phenylalanine (HL¹/HL⁴), isoleucine (HL²/HL⁵), and glycine (HL³/HL⁶), have been synthesized and characterized by elemental analysis, molar conductance, electronic, infrared, and multinuclear magnetic resonance (¹H and ¹³C) studies. In all cases, the Pb atom is in a four-coordinated environment with two bidentate deprotonated Schiff bases binding as monoanionic ligands through the oxygen and azomethine nitrogen. The 3D molecular modeling and analysis for bond lengths and bond angles have also been carried out for one of the representative compounds, [Pb(L³)₂] to substantiate the proposed structures.     

A new calix[4]arene based nucleobase for cation recognition

A novel calix[4]arene linked nucleobase molecular receptor bearing two adenine moieties has been synthesized and characterized by UV, IR, NMR and ESI–MS analyses. The synthesized receptor can recognize biologically important Zn²⁺ and Mn²⁺ ions through 1:1 binding stoichiometry. The evaluation of binding constants suggests that adenine alone, in an appropriate supramolecular network, can exhibit efficient binding for Zn²⁺ ions without the presence of any phosphate or sugar unit.     

Magnetically guided fast electrons in cylindrically compressed matter

Fast electrons produced by a 10 ps, 160 J laser pulse through laser-compressed plastic cylinders are studied experimentally and numerically in the context of fast ignition. K(α)-emission images reveal a collimated or scattered electron beam depending on the initial density and the compression timing. A numerical transport model shows that implosion-driven electrical resistivity gradients induce strong magnetic fields able to guide the electrons. The good agreement with measured beam sizes provides the first experimental evidence for fast-electron magnetic collimation in laser-compressed matter.     

Room temperature ferromagnetism in Zn1−xCoxS thin films with wurtzite structure

The magnetic properties of Zn_1−xCo_xS (x=0.025 and 0.05) thin films grown on α-quartz substrates at different temperatures (T_S) of 200, 400 and 600 °C by means of pulsed laser deposition are presented. The films are crystallized with wurtzite structure. Optical absorption and transmission electron microscopy measurements indicate that Co ions are substituted to Zn on tetrahedral sites. Their magnetic response is composed of ferromagnetic and paramagnetic components of which respective strengths depend on T_S and Co concentration. This behavior is interpreted as due to fluctuations in the magnetic ordering, depending on grain size and site location in grain boundaries or in crystal cores.     

Performance of CeO2–TiO2-admixed photoelectrode for natural dye-sensitized solar cell

Extracts from roots of Beta vulgaris were used as natural sensitizers of a wide-bandgap semiconductor (CeO₂–TiO₂) in photoelectrochemical solar cells. The natural dye, adsorbed onto the semiconductor surface, absorbs visible light and promotes electron transfer across the dye/semiconductor interface. We have applied CeO₂–TiO₂ to natural dye sensitizer solar cells as a photoelectrode to reduce the charge recombination rate by providing energy barrier at the interface between the photoanode and electrolyte which offers an improvement of photovoltaic efficiency. Short-circuit current density (J _sc) and open-circuit voltages (V _oc) of 9.0 mA cm^?2 and 680 mV, respectively, were obtained, and an effective energy conversion efficiency of 3.5?% was achieved. This simple and cheap technique of cell preparation opens up a perspective of commercial feasibility for inexpensive and environment-friendly dye cells.     

Spectrophotometric determination of ruthenium with diphenylthiovioluric acid

Diphenylthiovioluric acid (DPHTVA) reacts with ruthenium(III) to form a complex which has an absorbance maximum at 520 nm. Effects of pH, heating time, buffer and reagent have been studied. DPHTVA has been found to be a sensitive reagent for ruthenium(III) (sensitivity = 0.0044 μg Ru/cm² for log I₀/I = 0.001), and has been made selective by the use of masking agents. The composition of the complex as revealed by different methods is 1:2 (ruthenium:DPHTVA).     

Optimal approximate formulas with polynomial precision

For any given linear functional bounded over the Hardy spaceH ², we obtain explicitly optimal approximate formulas, with polynomial precision, based on nodes lying equispaced on |z|=r. In particular, we obtain optimal formulas with polynomial precision for interpolation, numerical differentiation and integration.     

Studies in sesquiterpenes—LVII: Isolongifolene (part 8): solvolysis of 8-bromoneoisolongifolene

Acetolysis of 8-bromoneoisolongifolene generates, besides two normal products (of elimination and S_N2 displacement), which were minor, one rearranged elimination product and a tertiary acetate. The rearranged diolefine arises from acetic acid-catalysed rearrangement of the normal elimination product, while the tertiary acetate is a Wagner substitution product arising from a syn-migration. In this context various factors controlling such migrations are discussed and, the possible role of energetics of the incipient carbonium ion at the migration origin highlighted.     

Highly excited,normally inaccessible vibrational levels by sub-doppler modulated gain spectroscopy: The Na2 A1Σ+u state

Modulated gain spectroscopy is a sensitive, widely applicable, rovibronically state selective, sub-Doppler, triple resonance method for examining excited vibronic levels which are Franck—Condon inaccessible from thermally populated levels of the electronic ground state. A cw optically pumped molecular laser (OPL) prepares a steady-state population in a selected, vibrationally highly excited, rotation-vibration level of the electronic ground state (the lower level of the OPL transition). An intensity-modulated, single frequency dye laser excites part of this intracavity OPL-prepared population to the level of interest, thereby causing an increase in the OPL population inversion density, and, in turn, its output power. As the frequency of the dye laser is scanned, resonances are selectively detected by the appearance of modulation on the OPL output power; discrimination against dye laser excitations out of levels unconnected with the OPL is nearly perfect. Sub-Doppler (≈300 MHz FWHM) transitions are observed, thereby extending knowledge of the Na₂A¹Σ⁺_u state from v=44 to 62.