Phenol side‐groups‐containing fluorene polymer synthesized by catalytic oxidative polymerization

Catalytic oxidative polymerization (OP) of 4,4'‐(fluorene‐9,9‐di‐yl)diphenol (FDP), possessing both phenol and fluorene rings in its structure, was carried out in different organic solvents. Schiff base polymer‐copper (II) complex and hydrogen peroxide were used as a catalyst and an oxidizing agent, respectively. The structure of poly (4,4'‐(fluorene‐9,9‐di‐yl)diphenol) (PFDP) was confirmed by UV–vis, FT‐IR, NMR spectroscopies. Further characterization was conducted by means of thermogravimetric analysis (TGA), DSC, XRD, scanning electron microscopy (SEM), cyclic voltammetry (CV), and conductivity measurements. PFDP showed the optical band gap of 3.09 eV, the emission maximum at 335 nm, and the HOMO level of ?5.75 eV. Copyright © 2010 John Wiley & Sons, Ltd.     

Quantum chemical studies on prototautomerism of 1H‐imidazo[4,5‐c]pyridine

The structural features of the 1H‐imidazo[4,5‐c]pyridine (ICPY) tautomers and homodimers of the most stable tautomers have been studied by quantum chemical methods. FTIR and Raman spectra of the ICPY were recorded in the range of 4000–60 cm^?1 and 3500–5 cm^?1. The predominant tautomer among four possible isomers of ICPY were determined. The optimized geometries and vibrational frequencies of possible ICPY tautomers and dimers were computed by B3LYP/DFT method with 6‐311++G(d,p) and 6‐31G(d) basis sets. All vibrational frequencies assigned in detail with the help of total energy distribution (TED) and isotopic shifts. ICPY dimeric forms were also characterized according to their hydrogen bonding interactions, and it has been found that the most stable ICPY homodimer establishes moderate strong N ? H …N type hydrogen bond. ¹H NMR, ¹³C NMR, and ¹⁵N NMR properties have been calculated for all tautomeric forms using the gauge independent atomic orbital (GIAO) method. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Ligandless-solidified floating organic drop microextraction method for the preconcentration of trace amount of cadmium in water samples

In this article, a new ligandless solidified floating organic drop microextraction (LL-SFODME) method has been developed for preconcentration of trace amount of cadmium as a prior step to its determination by flow injection-flame atomic absorption spectrometry (FI-FAAS). The methodology is based on the SFODME of cadmium with 1-dodecanol in the absence of chelating agent. Several factors affecting the microextraction efficiency, such as, pH, sodium dodecylbenzenesulfonate (SDBS) concentration, extraction time, stirring rate and temperature were investigated and optimized. Under optimized experimental conditions an enhancement factor of 205 was obtained for 100 mL of sample solution. The calibration graph was linear in the range of 1.0-25.0 ng mL⁻¹, the limit of detection (3s) was 0.21 ng mL⁻¹ and the limit of quantification (10s) was 0.62 ng mL⁻¹. The relative standard deviation (RSD) for 10 replicate measurements of 10 ng mL⁻¹ cadmium was 4.7%. The developed method was successfully applied to the extraction and determination of cadmium in standard and several water samples and satisfactory results were obtained.     

Synthesis and antitumor activity of new silver(I)-N-heterocyclic carbene complexes

Abstract

In this study, two novel benzimidazole-based N-heterocyclic carbene ligands (1a-b) and their silver(I) complexes (2a-b) were synthesized. All new compounds were characterized by FT-IR, LC-MS, ¹H NMR, and ¹³C NMR spectroscopies. The in vitro antitumor activities of NHC ligands (1a-b) and their silver(I) complexes (2a-b) against DU-145 human prostate cancer cells, MDA-MB-231 and MCF-7 human breast cancer cells and L-929 (normal cells adipose from mouse) were also determined using MTT analysis for 24?h, 48?h, and 72?h. The results showed that while NHC ligands did not have in vitro antitumor activity on MCF-7, MDA-MB-231 and DU-145 cells, Ag(I)-NHC complexes have in vitro antitumor activities. The in vitro antitumor activity of 2a was found to be lower than that of 2b. Ag(I)-NHC complexes were observed to have higher IC₅₀ values for non-cancerous cell lines than cancer cells.     

Pseudosymmetric Lightlike Hypersurfaces in Indefinite Sasakian Space Forms

We study pseudosymmetric lightlike hypersurfaces of an indefinite Sasakian space form, tangent to the structure vector field. We obtain sufficient conditions for a lightlike hypersurface to be pseudosymmetric, pseudoparallel and Ricci-pseudosymmetric in an indefinite Sasakian space form. We also find certain conditions for a pseudosymmetric lightlike hypersurface of an indefinite Sasakian space form to be totally geodesic and check the effect of Weyl projective pseudosymmetry conditions on the geometry of a lightlike hypersurface of an indefinite Sasakian space form. Moreover we give some physical interpretations of pseudo-symmetry conditions.     

Studies on the Thermal Decompositions of Heteropolynuclear Glyoxylates of Cr(III) and Cu(II)

Complexes of Cr(III):Cu(II) with the glyoxylate dianion as ligand were synthesized in the range of cation atomic ratios (0.01–8):1.0. The results of non-isothermal analysis of the synthesized compounds correlated with the results of IR and UV-VIS spectroscopy, and gas chromatography of the volatile products of the decomposition allowed the formulation of a mechanism for the decomposition of the complex with Cr(III):Cu(II)=2:1 and the assumption that the other complexes are mixtures of this with the homopolynuclear complexes of Cr(III) and Cu(II), depending on the ratio of the cations Cr(III):Cu(II). The thermal conversion of the complexes takes place at relatively low temperatures, with partial transformation of the ligand into oxalate and of the oxide mixture into CuCrO₄. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of Ring Annelation on the Mode Selectivity of the Ionized Diazabicycloheptenes and Corresponding Housanes: An ESR and ENDOR Study

The tricyclic azoalkanes, (1α,4α,4aα,7aα)‐4,4a,5,6,7,7a‐hexahydro‐1,4,8,8‐tetramethyl‐1,4‐methano‐1H‐cyclopenta[d]pyridazine ( 1c ), (1α,4α,4aα,6aα)‐4,4a,5,6,6a‐pentahydro‐1,4,7,7‐tetramethyl‐1,4‐methano‐1H‐cyclobuta[d]pyridazine ( 1d ), (1α,4α,4aα,6aα)‐4,4a,6a‐trihydro‐1,4,7,7‐tetramethyl‐1,4‐methano‐1H‐cyclobuta[d]pyridazine ( 1e ), and (1α,4α,4aα,5aα)‐4,4a,5,5a‐tetrahydro‐1,4,6,6‐tetramethyl‐1,4‐methano‐1H‐cyclopropa[d]pyridazine ( 1f ), as well as the corresponding housanes, the 2,3,3,4‐tetramethyl‐substituted tricyclo[3.3.0.0^2,4]octane ( 2c ), tricyclo[3.2.0.0^2,4]heptane ( 2d ), and tricyclo[3.2.0.0^2,4]hept‐6‐ene ( 2e ), were subjected to γ‐irradiation in Freon matrices. The reaction products were identified with the use of ESR and, in part, ENDOR spectroscopy. As expected, the strain on the C‐framework increases on going from the cyclopentane‐annelated azoalkanes and housanes ( 1c and 2c ) to those annelated by cyclobutane ( 1d and 2d ), by cyclobutene ( 1e and 2e ), and by cyclopropane ( 1f ). Accordingly, the products obtained from 1c and 2c in all three Freons used, CFCl₃, CF₃CCl₃, and CF₂ClCFCl₂, were the radical cations 3c ^.+ and 2c ^.+ of 2,3,4,4‐tetramethylbicyclo[3.3.0]oct‐2‐ene and 2,3,3,4‐tetramethylbicyclo[3.3.0]octane‐2,4‐diyl, respectively. In CFCl₃ and CF₃CCl₃ matrices, 1d and 2d yielded analogous products, namely the radical cations 3d ^.+ and 2d ^.+ of 2,3,4,4‐tetramethylbicyclo[3.2.0]hept‐2‐ene and 2,3,3,4‐tetramethylbicyclo[3.2.0]heptane‐2,4‐diyl. The radical cations 3c ^.+ and 3d ^.+ and 2c ^.+ and 2d ^.+ correspond to their non‐annelated counterparts 3a ^.+ and 3b ^.+, and 2a ^.+ and 2b ^.+ generated previously under the same conditions from 2,3‐diazabicyclo[2.2.1]hept‐2‐ene ( 1a ) and bicyclo[2.1.0]pentane ( 2a ), as well as from their 1,4‐dimethyl derivatives ( 1b and 2b ). However, in a CF₂ClCFCl₂ matrix, both 1d and 2d gave the radical cation 4d ^.+ of 2,3,3,4‐tetramethylcyclohepta‐1,4‐diene. Starting from 1e and 2e , the radical cations 4e ^.+ and 4e′ ^.+ of the isomeric 1,2,7,7‐ and 1,6,7,7‐tetramethylcyclohepta‐1,3,5‐trienes appeared as the corresponding products, while 1f was converted into the radical cation 4f ^.+ of 1,5,6,6‐tetramethylcyclohexa‐1,4‐diene which readily lost a proton to yield the corresponding cyclohexadienyl radical 4f ^.. Reaction mechanisms leading to the pertinent radical cations are discussed.     

Crystal Structure of 2-((<Emphasis Type="Italic">E</Emphasis>)-(5-Bromo-2- hydroxybenzylidene)hydrazono)-1,2-diphenylethanone

The molecular structure of the title compound, C₂₁H₁₅Br₁N₂O₂, was characterized by single crystal X-ray diffraction. The compound crystallizes in the triclinic sp. gr. \(P\bar 1\) with Z = 2. The molecule is not planar: the dihedral angle between the planes of two aromatic rings [C1/C6] and [C16/C21] is 84.9(2)°. The other dihedral angle between two aromatic rings [C9/C14] and [C16/C21] is 88.8(2)°. The title compound exists as a phenol-imine tautomer, in which a strong intramolecular O–H···N hydrogen bond is formed. This study verifies the preference of the phenol-imine tautomeric form in the solid state. A π–π stacking interactions are also observed, which may influence crystal stability: the distance between centroids is 3.702(2) Å.     

Influence of Dispersing Agents on the Solubility of Perovskites in Water

In this study, solubility behavior of lead magnesium niobate (PMN) powders in water was investigated in the presence of pure polyacrylic acid and polyacrylic acid/polyethylene oxide comb polymers. Experiments were performed by measuring the solubility of PMN in terms of the concentration of Pb⁺² and Mg⁺² ions in supernatant as a function of pH and dispersing agent dosage. The concentrations of the metal ions in supernatant were found to be affected by the dispersant concentration, stirring time and the suspension pH. Results revealed that both dispersing agents enhance the cation dissolution from PMN surface at pH 9 due to weak (reversible) adsorption and complexation of Pb⁺² and Mg⁺² by carboxylate groups. On the other hand, under acidic conditions cation dissolution from PMN is inhibited and this was attributed to the strong adsorption of dispersing agents onto the powder surface and formation of a dense polymer layer.