Fluorescence of Zn(II) 8-hydroxyquinoline complex in the presence of aqueous micellar media: The special cetyltrimethylammonium bromide effect

Mixtures of Zn(II) and 8-hydroxyquinoline (8QOH) in a 1:2 proportion, in aqueous solutions, result in fast complexation, followed by precipitation. Addition of 0.05 M sodium dodecyl sulfate (SDS), N-dodecyl-N,N-dimethylammonio-1-propanesulfonate (SB3-12), N-hexadecyl-N,N-dimethylammonio-1-propanesulfonate (SB3-16) or Triton X-100 results in considerable retardation of precipitation. In the presence of SDS, SB3-12, SB3-16 and Triton X-100 the 8QOH chelates are only kinetically stable in solution and after 24 h, the precipitation is almost quantitative. Conversely, upon addition of the cationic surfactant hexadecyltrimethylammonium bromide (CTABr), the absorbance of the complex remains constant even after at least six months. The interaction of the ligand 8QOH (and of the (8QO)(2)Zn(II) complex) with the cationic surfactant was studied by ultraviolet and NMR spectroscopy and 8QOH has a pK(a)=9.05 in the presence of the cationic surfactant and the ligand intercalates in the micelle, being preferentially located near the headgroup of the micelle. Although the solubilization site of the (8QO)(2)Zn(II) complex is similar to that of 8QOH, the interaction of the aromatic moiety with the CTA(+) headgroup is much stronger, due to the increased electron density in the aromatic ring of the ligand. As a consequence of this interaction, sphere to rod transition and an increase in microscopic and macroscopic viscosity are observed.     

Phase diagrams of the spin-2 Ising model in the presence of a quenched diluted crystal field distribution

We have investigated the random crystal field effects on the phase diagrams of the spin-2 Blume-Capel model for a honeycomb lattice using the effective-field theory with correlations.To do so,the thermal variations of magnetization are studied via calculating the phase diagrams of the model.We have found that the model displays both second-order and first-order phase transitions in addition to the tricritical and isolated points.Reentrant behavior is also observed for some appropriate values of certain system parameters.Besides the usual ground-state phases of the spin-2 model including ±2,±1,and 0,we have also observed the phases ±3/2 and ±1/2,which are unusual for the spin-2 case.     

Synthesis,electrochemistry, and electrocatalytic activity of thiazole-substituted phthalocyanine complexes

Journal of Solid State Electrochemistry - We report the synthesis of non-peripheral metallophthalocyanines which carry four 4-(4-methoxyphenyl)-2-thiazole-2-thio units. 1H-NMR, FT-IR, UV–Vis,...     

Direct Synthesis of Allylic Thioethers Under Greener Conditions: A Solvent- and Catalyst-Free Approach

We present herein a new catalyst-free and solvent-free approach for the synthesis of allylic thioethers directly from allylic alcohols and thiols. The methodology allows the synthesis of different allylic thioethers in good to excellent yields under microwave irradiation. Theoretical calculations for the allylic carbocation helped to explain the regioselectivity observed when nonsymmetric substrates are used in the reaction.     

Remarkable bismuth-gold alloy decorated on MWCNT for glucose electrooxidation: the effect of bismuth promotion and optimization via response surface methodology

In this study, the carbon nanotube supported gold, bismuth, and gold-bismuth(Au/MWCNT, Bi/MWCNT, and Au-Bi/MWCNT) nanocatalysts were prepared with NaBH₄ reduction method at varying molar atomic ratio for glucose electrooxidation (GAEO). The synthesized nanocatalysts at different Au: Bi atomic ratios are characterized via x - ray diffraction (XRD), transmission electron microscopy (TEM), and N₂ adsorption-desorption. For the performance of AuBi/MWCNT for GAEO, electrochemical measurements are performed by using different electrochemical techniques namely cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). Monometallic Au/MWCNT exhibits higher activity than Bi/MWCNT with 256.57 mA/mg (0.936 mA/cm²) current density. According to CV results, Au₈₀Bi₂₀/MWCNT nanocatalyst has the highest GAEO activity with the mass activity of 320.15 mA/mg (1.133 mA/cm²). For Au₈₀Bi₂₀/MWCNT, central composite design (CCD) is utilized for optimum conditions of the electrode preparation. Au₈₀Bi₂₀/MWCNT nanocatalysts are promising anode nanocatalysts for direct glucose fuel cells (DGFCs).     

Reaction of 1,2-bis(2,6-dicarboxypyridin-4-yl)ethyne with Co(II) generates coordination monomers not polymers: Crystal structure of 4-(2,6-dicarboxypyridin-4-yl)ethynylpyridine-2,6-dicarboxylatotriaqua cobalt(II) monohydrate

Reaction and crystallization of 1,2-bis(2,6-dicarboxypyridin-4-yl)ethyne with Co(II) produces crystals containing monomers of 4-(2,6-dicarboxypyridin-4-yl)ethynylpyridine-2,6-dicarboxylatotriaqua cobalt(II) monohydrate complex (1), [Co(C₁₆H₆N₂O₈)(H₂O)₃]·H₂O, instead of a rigid 1-D metal–organic framework consisting of a linear coordination polymer. This complex crystallizes in the monoclinic space group C2/c with a=6.8028(9) ?, b=36.781(5) ?, c=7.5135(9) 2.474(2)° and Z=4. The complex sits on a symmetry axis such that the two halves of the molecule are related by two-fold rotation symmetry. The molecules form layers in which the molecules are joined by intermolecular O–H⋯O interactions involving hydrogen bonds between CO₂H⋯CO₂ ⁻, H₂O⋯CO₂ ⁻, H₂O⋯CO₂H and H₂O⋯H₂O groups.Supplementary material CCDC-289569 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data request/cif, by e-mailing data request@ccdc.cam.ac.uk or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 IEZ, UK; fax: +44(0)1223-336033.     

Specific anion binding to sulfobetaine micelles and kinetics of nucleophilic reactions

With fully micellar bound substrates reactions of OH- with benzoic anhydride, Bz(2)O, and of Br- with methyl naphthalene-2-sulfonate, MeONs, in micellized sulfobetaines are strongly inhibited by NaClO4 which displaces the nucleophilic anions from the micellar pseudophases. Micellar incorporations of ClO4- and Br- are estimated with an ion-selective electrode and by electrophoresis, and partitioning of Br- between water and micelles is related to changes in NMR spectral (79)Br- line widths. Extents of inhibition by ClO4- of these nucleophilic reactions in the micellar pseudophase are related to quantitative displacement of the reactive anions from the micelles by ClO4-. The kinetic data are correlated with physical evidence on the strong interactions between sulfobetaines and ClO4-, which turn sulfobetaine micelles anionic and effectively provoke displacement of OH- and Br-.     

The chameleon-like nature of zwitterionic micelles. Control of anion and cation binding in sulfobetaine micelles. Effects on acid equilibria and rates

The rate of specific hydrogen ion catalyzed hydrolysis of 2-(p-heptoxyphenyl)-1,3-dioxolane and equilibrium protonation of 1-hydroxy-2-naphthoate ion in zwitterionic micelles of SB3-14, C14H29NMe2+(CH2)3SO3-, are increased markedly by NaClO4 which induces anionic character and uptake of H3O+ in the micelles. Other salts, for example, NaNO3, NaBr, and NaCl, have similar but much smaller effects on this uptake of H3O+.