Cu (DPM)2–initiated vinyl polymerization

The behavior of cupric dipivaloylmethide in vinyl polymerization systems was investigated with a view to understanding the mechanism of polymerization initiation. Results of polymerization reactions together with spectral investigation data are presented. Polymerization in the presence of the chelate proceeds through a free-radical process. The corresponding kinetic and transfer constants and activation energy values suggest a normal propagation step. With the help of spectral data an attempt is made to suggest a plausible mechanism of initiation.     

Baeyer‐Villiger oxidation of cyclopentanone over zeolite Y entrapped transition metal‐Schiff base complexes

Transition metal [M = VO (IV) and/or Cu (II)] complexes with Schiff base ligand, (Z)‐2‐((2‐hydroxybenzylideneamino)phenol (H₂L) have been entrapped in the super cages of zeolite‐Y by Flexible Ligand Method. Synthesized materials have been characterized by preferential physico‐chemical techniques such as inductively coupled plasma optical emission spectroscopy (ICP‐OES), elemental analyses (CHN), fourier transmission infrared spectroscopy (FTIR), electronic and UV‐reflectance spectra, Brunauer–Emmett–Teller (BET) surface area measurements, scanning electron micrographs (SEMs), X‐ray diffraction patterns (XRD) and thermogravimetric analysis (TGA). The catalytic competence of zeolite‐Y entrapped transition metal complexes was examined in Baeyer‐Villiger (BV) oxidation of cyclopentanone using 30% H₂O₂ as an oxidant beside neat complexes to check the aptitude of heterogeneous catalysis over the homogeneous system. The effect of experimental variables such as mole ratio of substrate to an oxidant, amount of catalyst, reaction time, varying oxidants and solvents on the conversion of cyclopentanone was also tested. Under the optimized reaction conditions, one of the zeolite‐Y entrapped transition metal complex viz. [VO(L)H₂O]‐Y [where L = (Z)‐2‐((2‐hydroxybenzylideneamino)phenol] was found to be a potential contender by providing 80.22% conversion of cyclopentanone (TON: 10479.42), and the selectivity towards δ‐valerolactone was 83.56%.     

Pyrene functionalized oxacalix[4]arene architecture as dual readout sensor for expeditious recognition of cyanide anion

A pyrene functionalized oxacalix[4]arene architecture (DPOC) was utilized as a fluorescence probe for selective recognition of cyanide ions. The receptor DPOC shows excellent selectivity towards cyanide ion with a red shift of 108 nm in absorption band along with a significant change in colour from light yellow to pink. The fluorescence titration experiments further confirm the lower limit of detection as 1.7µM with no significant influences of competing anions. ¹ H-NMR titration experiments support the deprotonation phenomena, as the -NH proton disappears upon successive addition of cyanide ions. The DFT calculation also indicates a certain increment of -NH bond length upon interaction with cyanide ions. The spectral properties as well as colour of DPOC-CN^? system may be reversed upon the addition of Ag⁺/ Cu²⁺ ions up to 5 consecutive cycles. Moreover, DPOC coated “test strips” were prepared for visual detection of cyanide ions.

     

New products

SESAME (Synchrotron Light for Experimental Science and Applications in the Middle East) is an international synchrotron radiation project under the auspices of UNESCO. The physical site is located in Amman, Jordan. At press time, the building was scheduled for completion by March 2007.     

An Efficient Synthesis of Racemic and Optically Active Telluromethionine

A direct and efficient route for the construction of racemic and optically active L-telluromethionine (L-Te-Met) starting from the readily available hydrochloride salt of α-amino-γ-butyrolactone and lithium methyltellurolate is described. The reaction has been successfully scaled up to afford gram quantities of L-Te-Met in 75–80% yield.     

Novel drug‐based Fe(III) heterochelates: synthetic,spectroscopic, thermal and in‐vitro antibacterial significance

A series of novel heterochelates of the type [Fe(Aⁿ)(L)(H₂O)₂]^?mH₂O [where H₂Aⁿ = 4,4′‐(arylmethylene)bis(3‐methyl‐1‐phenyl‐4,5‐dihydro‐1H‐pyrazol‐5‐ol); aryl = 4‐nitrophenyl, m = 1 (H₂A¹); 4‐chlorophenyl, m = 2 (H₂A²); phenyl, m = 2 (H₂A³); 4‐hydroxyphenyl, m = 2 (H₂A⁴); 4‐methoxyphenyl, m = 2 (H₂A⁵); 4‐hydroxy‐3‐methoxyphenyl, m = 1.5 (H₂A⁶); 2‐nitrophenyl, m = 1.5 (H₂A⁷); 3‐nitrophenyl, m = 0.5 (H₂A⁸); p‐tolyl, m = 1 (H₂A⁹) and HL = 1‐cyclopropyl‐6‐fluoro‐4‐oxo‐7‐(piperazin‐1‐yl)‐1,4‐dihydroquinoline‐3‐carboxylic acid] were investigated. They were characterized by elemental analysis (FT‐IR, ¹H‐ & ¹³C‐NMR, and electronic) spectra, magnetic measurements and thermal studies. The FAB‐mass spectrum of [Fe(A³)(L)(H₂O)₂]^?2H₂O was determined. Magnetic moment and reflectance spectral studies revealed that an octahedral geometry could be assigned to all the prepared heterochelates. Ligands (H₂Aⁿ) and their heterochelates were screened for their in‐vitro antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Serratia marcescens bacterial strains. The kinetic parameters such as order of reaction (n), the energy of activation (E_a), the pre‐exponential factor (A), the activation entropy (ΔS^#), the activation enthalpy (ΔH^#) and the free energy of activation (ΔG^#) are reported. Copyright © 2009 John Wiley & Sons, Ltd.     

Novel Fe (III) heterochelates: Synthesis,structural features and fluorescence studies

Fluorescence properties of five 4-acyl pyrazolone based hydrazides (H₂SB_n) and their Fe (III) heterochelates of the type [Fe(SB_n)(L)(H₂O)]·mH₂O [H₂SB_n = nicotinic acid [1-(3-methyl-5-oxo-1-phenyl-4,5-di hydro-1H-pyrazol-4yl)-acylidene]-hydrazide; where acyl = –CH₃, m = 4 (H₂SB₁); –C₆H₅, m = 2 (H₂SB₂); –CH₂–CH₃, m = 3 (H₂SB₃); –CH₂–CH₂–CH₃, m = 1.5 (H₂SB₄); –CH₂–C₆H₅, m = 1.5 (H₂SB₅) and HL = 1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid] were studied at room temperature. The fluorescence spectra of heterochelates show red shift, which may be due to the chelation by the ligands to the metal ion. It enhances ligand ability to accept electrons and decreases the electron transition energy. The kinetic parameters such as order of reaction (n), energy of activation (E_a), entropy (S*), pre-exponential factor (A), enthalpy (H*) and Gibbs free energy (G*) have been reported.     

Metabolic profiling of Escherichia coli by ion mobility-mass spectrometry with MALDI ion source

Comprehensive metabolome analysis using mass spectrometry (MS) often results in a complex mass spectrum and difficult data analysis resulting from the signals of numerous small molecules in the metabolome. In addition, MS alone has difficulty measuring isobars and chiral, conformational and structural isomers. When a matrix-assisted laser desorption ionization (MALDI) source is added, the difficulty and complexity are further increased. Signal interference between analyte signals and matrix ion signals produced by MALDI in the low mass region (<1500 Da) cause detection and/or identification of metabolites difficult by MS alone. However, ion mobility spectrometry (IMS) coupled with MS (IM-MS) provides a rapid analytical tool for measuring subtle structural differences in chemicals. IMS separates gas-phase ions based on their size-to-charge ratio. This study, for the first time, reports the application of MALDI to the measurement of small molecules in a biological matrix by ion mobility-time of flight mass spectrometry (IM-TOFMS) and demonstrates the advantage of ion-signal dispersion in the second dimension. Qualitative comparisons between metabolic profiling of the Escherichia coli metabolome by MALDI-TOFMS, MALDI-IM-TOFMS and electrospray ionization (ESI)-IM-TOFMS are reported. Results demonstrate that mobility separation prior to mass analysis increases peak-capacity through added dimensionality in measurement. Mobility separation also allows detection of metabolites in the matrix-ion dominated low-mass range (m/z < 1500 Da) by separating matrix signals from non-matrix signals in mobility space.     

On the controversy of metal ion composition on amine oxygenase (AurF): a computational investigation

An energetics-spectroscopic approach based on DFT method reveals that the active site structure of AurF has {Fe(III)(2)O} central core with one protonated terminal glutamate.