Synthesis and Crystal Structure of a Decamethyleuropocene Complex Supported by a “Clamshell” Ligand

Abstract  

The coordination of decamethyleuropocene to a “clamshell” 1,2-bis(imino)acenaphthene (BIAN) ligand is accompanied by a one-electron redox process. The crystal structure of the Eu³⁺ product has been determined. The complex crystallizes in the triclinic space group P-1, with a = 12.065(2), b = 15.391(3), c = 17.266(4) ?, α = 73.71, β = 73.93(3), γ = 81.40(3)°, V = 2948.3(10) ?³ and Z = 2. The pyridine moiety of the clamshell ligand is not coordinated to the Eu³⁺ center.     

Electrochemical bromination of cyclic and acyclic enes using biphasic electrolysis

A simple method of electrochemical bromination of a series of cyclic and acyclic enes (styrene and substituted styrenes, stilbene, indene, and cyclooctene) in a biphasic water–chloroform mixture mediated by bromide/bromine redox system is reported. Aqueous 25% NaBr/H₂SO₄ is used as the electrolyte. Regio- and stereoselective dibromination of enes is achieved. Moderate to excellent yields of the product (83–98%) is obtained depending on the substrate. Electrolyte reuse has also been demonstrated successfully using HBr in the dibromination of styrene.     

Aromatic molecules in restricted geometries: photophysics of naphthalene included in a cyclodextrin functionalized layered solid

The galleries of an Mg-Al layered double hydroxide have been functionalized by intercalation of carboxymethyl beta-cyclodextrin cavities. The anchored cavities form a random array of identical-sized hydrophobic nanopockets arranged in a bilayer fashion in the interlamellar space of the layered solid. Naphthalene molecules have been included within these cavities by partitioning from a polar solvent. The fluorescence from the included naphthalene shows an unusual behavior--the excimer to monomer emission intensity decreases with increasing concentration of included naphthalene. This is shown to be a consequence of the absence of translational mobility of the naphthalene--cyclodextrin adduct in the functionalized solid. Two types of included naphthalene have been identified: a preformed excimer-like species characterized by the absence of rise time in decay measurements and a monomeric species that is incapable of excimer formation due to the absence of suitably located included naphthalenes in its proximity. The concentration of each species and the enthalpy for excimer formation have been determined from the temperature variation of fluorescence intensities.     

Rapid identification and quantification of chlorpheniramine maleate or pheniramine maleate in pharmaceutical preparations by thin-layer chromatography-densitometry

Thin-layer chromatography (TLC)-densitometry was used to separate, identify, and quantitate chlorpheniramine maleate (CPM) and pheniramine maleate (PM) when present in combination with other drugs in pharmaceutical preparations of tablets, syrups, eye and ear drops, etc. CPM or PM was extracted (tablets, capsules, etc.) or diluted (liquid preparations, if needed) with 80% ethanol and isolated from other ingredients by TLC on silica gel G using cyclohexane-chloroform-methanol-diethylamine (4.5 + 4.0 + 0.5 + 1.0, v/v) as the mobile phase. Separated CPM and PM were detected under shortwave ultraviolet light and quantitated by scanning densitometry at 260 nm. Recoveries of CPM and PM were 100.09+/-0.77% and 100.09+/-0.87%, respectively.     

High‐temperature shock tube study of the reactions CH3 + OH → products and CH3OH + Ar → products

The reaction between methyl and hydroxyl radicals has been studied in reflected shock wave experiments using narrow‐linewidth OH laser absorption. OH radicals were generated by the rapid thermal decomposition of tert‐butyl hydroperoxide. Two different species were used as CH₃ radical precursors, azomethane and methyl iodide. The overall rate coefficient of the CH₃ + OH reaction was determined in the temperature range 1081–1426 K under conditions of chemical isolation. The experimental data are in good agreement with a recent theoretical study of the reaction. The decomposition of methanol to methyl and OH radicals was also investigated behind reflected shock waves. The current measurements are in good agreement with a recent experimental study and a master equation simulation. © 2008 Wiley Periodicals, Inc. 40: 488–495, 2008     

Platinum particles dispersed poly(diphenylamine) modified electrode for methanol oxidation

A modified potentiostatic method, termed the ‘pulse pontentiostatic method’ (PPSM) was used to get nano fibrillar poly(diphenylamine) (PDPA) film on Indium tin oxide (ITO) coated glass electrode and also for making modified electrode with platinum particles dispersed in PDPA. Platinum clusters were electrodispersed under constant potential on PDPA films to obtain catalytic electrodes for methanol oxidation. Energy dispersive analysis of X-rays (EDAX) results showed that the Pt microparticles are deposited into PDPA film. Scanning electron micrograph, SEM images show that the deposition results spherical catalytic particles. X-ray photoelectron spectroscopy (XPS) results inform that the net electronic charge on carbon atom and also the imine/amine ratio was not affected by Pt loadings. The modification of electrode surface by nano fibular PDPA improves the electrocatalytic activity for methanol oxidation.     

Computation of heat transfer enhancement in a plate‐fin heat exchanger with triangular inserts and delta wing vortex generator

Longitudinal vortices disrupt the growth of the thermal boundary layer, thereby the vortex generators producing the longitudinal vortices are well known for the enhancement of heat transfer in compact heat exchangers. The present investigation determines the heat transfer characteristics with secondary flow analysis in plate fin triangular ducts with delta wing vortex generators. This geometrical configuration is investigated for various angles of attack of the wing i.e. 15°, 20°, 26° and 37° and Reynolds numbers 100 and 200. The constant wall temperature boundary condition is used. The solution of the complete Navier Stokes equation and the energy equation is carried out using the staggered grid arrangement. The performance of the combination of triangular secondary fins and delta wing with stamping on slant surfaces has also been studied. Copyright © 2009 John Wiley & Sons, Ltd.     

An elastic wave scattering problem relating to the rapid movement of a fracture in a plate: Part II — Numerical results

In Part I of this two part paper, we developed analytical expressions for the crack face displacements due to an applied point traction as well as a moving point source of dilatation. In this sequel to Part I, we present numerical results for the crack face displacements in the form of displacement-time records at fixed locations on the crack face. For the stationary point traction problem, the results are more or less in keeping with the predictions made in Part I, with the Rayleigh pulse giving a large contribution for an applied step load.In the case of the moving point microfracture with a step time dependence, in addition to the diffracted compressional, shear and Rayleigh arrivals there is observed the evolution of a new pulse whose amplitude and position on the time record shifts changes if the calculations are done for a different crack speed. Results are also presented for a microfracture with an oscillatory time dependence. Once again, the first arrival of the surface pulse appears to be the most prominent arrival on the record. Further explorations of the parameters and source functions would be required before comparisons with experimental data can be made.     

Dications of benzylidenefluorene and diphenylmethylidene fluorene: the relationship between magnetic and energetic measures of antiaromaticity

Oxidation of m- and p-substituted benzylidene fluorenes to antiaromatic dications was attempted by electrochemical and chemical means. Electrochemical oxidation to dications was successful for benzylidene fluorenes with p-methoxy, p-methyl, p-fluoro, and unsubstituted phenyl rings in the 3-position; attempts to oxidize the m-substituted derivatives via electrochemistry were unsuccessful. Chemical oxidation with SbF(5)/SO(2)ClF gave the dication of 9-[(4-methoxyphenyl)methylene]-9H-fluorene cleanly; oxidation of all other substituted benzylidene fluorenes resulted in mixtures of products. The excellent linear relationship between the chemical shifts calculated by the GIAO method and the experimental shifts for the p-methoxy-substituted benzylidene fluorene dication suggests that the calculations satisfactorily reflect the magnetic properties of this dication and potentially those of the other dications studied. The redox potentials from electrochemical oxidation, a measure of the stability of the dications, showed a good linear relationship with another measure of stability, the calculated difference in energy between each dication and its neutral precursor. The dications of benzylidene fluorenes were less stable than the dications of diphenylmethylidene fluorenes; within each type of compound, dications with p-substituted phenyl rings were more stable than dications with m-substituted phenyl rings and dications with phenyl rings substituted with electron-donating groups were more stable than dications with phenyl rings substituted with electron-withdrawing groups. The antiaromaticity of the fluorenyl system was assessed through the nucleus-independent chemical shift (NICS) that was also calculated by the GIAO method. The plot of the NICS values per square area versus the calculated energy difference for the dications showed a moderate degree of linearity; the plot of NICS values per square area versus the oxidation potentials was less linear. Thus, a suggestive, but not conclusive, relationship between magnetic and energetic measures of antiaromaticity was observed.