Stereoselective synthesis of 3,4-trans-disubstituted pyrrolidines and cyclopentanes via intramolecular radical cyclizations mediated by CAN

The stereoselective intramolecular cyclizations of bis(cinnamyl)tosylamides and dimethyl bis(cinnamyl)malonates mediated by cerium(IV) ammonium nitrate leading to the synthesis of 3,4-trans-disubstituted pyrrolidines and cyclopentanes are described.     

Synthesis, Characterization, Electrochemical Properties and Antibacterial Activity of Some Transiton Metal Complexes with [(2-hydroxy-1-naphthaldehyde)-3-isatin]-bishydrazone

A bishydrazone was prepared by reacting isatin monohydrazone with 2-hydroxy-1-naphthaldehyde and a series of metal complexes with this new ligand were synthesised by reaction with Mn^II, Fe^II, Co^II, Ni^II, Cu^II and Zn^II salts. The complexes were characterised on the basis of elemental analysis, molar conductance, magnetic susceptibility data, u.v.–visible, i.r., e.s.r. and n.m.r. spectral studies, wherever possible and applicable. Analytical data reveal that the nickel(II), copper(II) and zinc(II) complexes possess 1:1 metal–ligand ratios and that manganese(II), iron(II) and cobalt (II) complexes exhibit 1:2 ratios. Infrared spectral data suggest that the bishydrazone behaves as a monobasic tridentate ligand with ONO donor sequence towards the metal ions. X-ray diffraction study of the copper(II) complex indicated an orthorhombic crystal lattice. The e.p.r. spectral data show that the metal–ligand bond has considerable covalent character. The electrochemical behaviour of the copper(II) complex was investigated by cyclic voltammetry (CV). Antibacterial tests of the ligand and the metal complexes were also carried out and it has been observed that the complexes are more potent bactericides than the ligand.     

Cerium(IV) ammonium nitrate-mediated oxidative rearrangement of cyclobutanes and oxetanes

A facile CAN-mediated oxidative rearrangement of alkoxyaryl cyclobutanes and oxetanes is described.     

Scanning electron microscopic studies on different habits of gel grown doped manganese carbonate crystals

The effect of impurities on the growth of manganese carbonate crystals has been studied. Stereophotogrammetric analysis showed that all crystal faces have the same Miller indices and the peanut-shaped forms are twins with twin axis 0001.     

Dielectric,thermal, and mechanical properties of CeO2‐filled HDPE composites for microwave substrate applications

Cerium oxide‐filled high density polyethylene (HDPE) composites for microwave substrate applications were prepared by sigma‐blend technique. The HDPE was used as the matrix and the dispersion of CeO₂ in the composite was varied up to 0.5 by volume fraction, and the dielectric properties were studied at 1 MHz and microwave frequencies. The variations of thermal conductivity (k_eff), coefficient of thermal expansion (α_c) and Vicker's microhardness with the volume fraction of the filler were also measured. The relative permittivity (ε_eff) and dielectric loss (tan δ) were found to increase with increase in CeO₂ content. For 0.4 volume fraction loading of the ceramic, the composite had ε_eff = 5.7, tan δ = 0.0068 (at 7 GHz), k_eff = 2.6 W/m °C, α_c = 98.5 ppm/°C, Vicker's microhardness of 18 kg/mm² and tensile strength of 14.6 MPa. Different theoretical approaches have been used to predict the effective permittivity, thermal conductivity, and coefficient of thermal expansion of composite systems and the results were compared with the experimental data. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 998–1008, 2010     

(1-x)MgAl2O4-xTiO2 dielectrics for microwave and millimeter wave applications

The MgAl₂O₄ ceramics were prepared by the conventional solid-state ceramic route and the dielectric properties studied in the microwave frequency region (3–13 GHz). The phase purity and crystal structure were identified using the X-ray diffraction technique. The MgAl₂O₄ spinel ceramics show interesting microwave dielectric properties (ε_r=8.75, Q_uxf=68900 GHz (loss tangent = 0.00017 at 12.3 GHz), τ_f=-75 ppm/°C). The MgAl₂O₄ has high negative τ_f, which precludes its immediate use in practical applications. Hence the microwave dielectric properties of MgAl₂O₄ spinels were tailored by adding different mole fractions of TiO₂. The ε_r and Q factor of the mixed phases were increased with the molar addition of TiO₂ into the spinel to form mixtures based on (1-x)MgAl₂O₄-xTiO₂ (x=0.0-1.0). For x=0.25 in (1-x)MgAl₂O₄-xTiO₂, the microwave quality factor reaches a maximum value of Q_uxf=105400 GHz (loss tangent = 0.00007 at 7.5 GHz) where ε_r and τ_f are 11.035 and -12 ppm/°C, respectively. The microwave dielectric properties of the newly developed 0.75MgAl₂O₄-0.25TiO₂ dielectric is superior to several commercially available low loss dielectric substrates. PACS 77.22.-d; 84.40.-x; 81.05.Je     

Novel synthesis of highly functionalized pyrazolines and pyrazoles by triphenylphosphine-mediated reaction of dialkyl azodicarboxylate with allenic esters

[reaction: see text] Reaction of the Huisgen zwitterion, derived from triphenylphosphine and dialkyl azodicarboxylate, with allenic esters affords highly functionalized pyrazolines and pyrazoles. The crystal structure of pyrazoline derivative 7a showed extensive C-H...O interactions. Pyrazole formation proceeds via a novel nitrogen to carbon migration of the carboalkoxy group.     

Synthesis,characterization, fluorescence imaging,and cytotoxicity studies of a uracil‐based azo derivative and its metal complexes

A uracil‐based heterocyclic azo derivative was prepared by coupling diazotized 5‐aminouracil with 2‐naphthol. This ligand, viz., 1‐(2,4‐dioxopyrimidine‐5‐yl)‐azo‐naphth‐2‐ol (HNAP), was used as a precursor for the synthesis of a series of complexes with manganese(II), cobalt(II), nickel(II), copper(II), and zinc(II) ions. Various physicochemical measurements UV–Visible, Infrared (IR), ¹H NMR, ¹³C Nuclear Magnetic Resonance (NMR), and electron spin resonance (ESR) spectral studies were employed to characterize the ligand and the metal complexes. The ligand showed good selectivity toward Mn²⁺ over the other metal ions with a detection limit of 1.36 μM. This probe was used for the confocal fluorescence imaging of Mn²⁺ ions in Michigan Cancer Foundation‐7 (MCF‐7) cells. The ligand and the metal complexes were tested for their cytotoxicity on the MCF‐7 cell line. It was observed that complexation of HNAP with the metal ions exhibited a promising cytotoxicity.     

Biocidal effects of photocatalytic semiconductor TiO2

Photocatalytic action of the commercial TiO₂ was the subject of study on the destruction of the microbes within the biofilms. The TiO₂ powder was characterized by X-ray diffraction (XRD) for identifying its type and the particle size was determined. The biofilm was allowed to form over TiO₂ coatings over glass slides irradiated with polychromatic light for different time durations and distances. It indicates that a five-fold decrease in bacterial count due to the formation of H₂O₂ at TiO₂/biofilm interface. The formation of H₂O₂ at the TiO₂/biofilm interface is estimated and it does not destroy the entire bacterial population within the biofilm. Bacterial killing effect is supported by FT-IR analysis.