Polymeric ionic liquids: a strategy for preparation of novel polymeric materials

A novel polymeric ionic liquid (PIL), bearing high C-N and N-N content, potentially suitable for new safe energetic materials and catalyst supports was introduced. The PIL was prepared by way of radical co-polymerisation of 1-vinyl-3-p-nitrobenzylimidazolium bromide and 1-vinylimidazole at 80°C using azobisisobutyronitrile (AIBN) as an initiator. The PIL thus produced was successfully transformed into NO₃@PIL and N₃@PIL for potential application as safe energetic materials and/or catalyst supports. The polymers were obtained in quantitative yields and were characterised by NMR, FTIR, DSC and TGA data. This study reveals the adequate thermal stability of novel salt-based nitrogen-rich polymeric ionic liquids for application as safe energetic materials and/or supports in heterogeneous catalysis.     

Analysis of the turbulent boundary layer in the vicinity of a self-excited cylindrical Helmholtz resonator

This study investigates the changes in the structure of a turbulent boundary layer downstream of a flow-excited Helmholtz resonator. To this end, a fully developed turbulent boundary layer over a resonator mounted flush with a flat plate was simulated by implementing a large eddy simulation (LES). To assist in understanding the effect of the resonator on the flow structure, a sensitivity study was undertaken by changing the main geometrical parameters of the resonator. The results demonstrated that when the boundary layer thickness equals the orifice length, the cross-stream component of velocity fluctuations penetrates the boundary layer, resulting in a reduction of the turbulence intensity by up to 12%. Therefore, it is concluded that a Helmholtz resonator has the potential to reduce the instabilities within the boundary layer. These investigations also assist in identifying the optimal parameters to delay turbulence events within the grazing flow using Helmholtz resonators.     

Synthesis of novel 3-substituted-5H-benzo[5,6][1, 4]thiazino[3,2-e][1,2,4]triazines and their 15-lipoxygenase inhibitory activity

A new group of 3-substituted-5H-benzo[5,6][1,4]thiazino[3,2-e][1,2,4]triazines was designed, synthesized and evaluated as inhibitors of 15-lipoxygenase (15-LO), and the results were compared with those of standard ligand 4-methyl-2-(4-methylpiperazin-1-yl)pyrimido[4,5-b][1,4]benzothiazine (4-MMPB). Among the newly designed ligands, compound 9e showed the best IC₅₀ of 15-LO inhibition (IC₅₀ = 38 µM). The docking calculations were performed in MOE software based on the function of force-field scoring, in order to study the interaction of these new compounds and standard ligand with 15-LO. The docking study implied that these ligands have hydrogen bond interaction with the residue of active site of 15-LO.     

Electrochemical quantification of copper-based alloys using voltammetry of microparticles: optimization of the experimental conditions

Voltammetry of microparticles has been used in this work for the qualitative and quantitative analyses of zinc, tin, lead and copper in binary, ternary or quaternary alloy samples. The analyses were carried out by spiking small amounts of the metals into a carbon paste electrode, after which they were anodically stripped off using differential pulse voltammetry. The work involved four separate experiments. The first one examined the type of electrolyte, which is suitable to identify the four elements. More specifically, the aim was to examine in which electrolyte all elements can be measured simultaneously–as would be the case in a quaternary copper alloy–without seeing any overlap in their current peaks. The second experiment focused on optimizing the measurement conditions with the aim of having the current peaks of each element well separated from the others. For this part, we made use of the central composite design. The aims were to: (i) maximize the separation between current peaks, (ii) determine which variable has a higher impact on the response, (iii) give an insight in the robustness of the method close to the optimum conditions and (iv) eventually show interactions between variables. In the third experiment, the four elements were quantified in their binary mixtures. Here, the percentage of the oxidation current for each metal, which is directly related to the ratio of the metal in the binary matrices, was employed for the calibration. Finally, in the last experiment, the elements were quantified in two real quaternary samples: a brass and a lead bronze.     

Blocking properties of gold electrodes modified with 4-nitrophenyl and 4-decylphenyl groups

The electrochemical properties of Au electrodes grafted with 4-nitrophenyl and 4-decylphenyl groups have been studied. The electrografting of gold electrode surface with aryl groups was carried out by electroreduction of the corresponding diazonium salts in acetonitrile. The nitrophenyl film growth on gold was examined by atomic force microscopy, electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy. These measurements showed that a multilayer film of nitrophenyl groups was formed. Cyclic voltammetry was used to study the blocking properties of aryl-modified gold electrodes towards the Fe(CN)₆^3−/4− redox system. The reduction of oxygen was strongly suppressed on these electrodes as evidenced by the rotating disc electrode results.     

Study of reaction between activated acetylenes and N,N′‐diethyl‐2‐thiobarbituric acid in the presence of isocyanides or triphenylphosphine

In a series of separate experiments reaction between N,N′‐diethyl‐2‐thiobarbituric acid and acetylenic diesters in the presence of isocyanides or triphenylphosphine led to highly functionalized 4H‐pyrano[2,3‐d]thiopyrimidine or 1,4‐di‐ionic organophosphorus derivatives. The ¹H NMR spectra of diethyl‐7‐(2,6‐dimethylphenylamino)‐4‐oxo‐2‐thio‐ 1,3‐diethyl‐4H‐pyrano[2,3‐d]pyrimidine‐5,6‐dicarboxylate showed dynamic NMR effect that was attributed to restricted rotation around the aryl‐nitrogen single bond. Activation free energy (ΔG^≠) for this process is about 54.85 ± 2 kJ mol⁻¹. Betaines as 1,4‐diionic organophosphorus compounds in this reaction are possessed of two vicinal stereogenic centers and exist in the solution as a mixture of two diastereoisomers. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:228–235, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20601     

Synthesis of new phosphonato esters by reaction between triphenyl or trialkyl phosphite and acetylenic diesters in the presence of NH‐containing compounds

The reaction between triphenyl or trialkyl phosphite and acetylenic esters in the presence of some heterocyclic or aromatic NH compounds such as thiazolidine‐2,4‐dione, 2‐methyl indole, 5‐bromoisatine, 3‐nitroacetanilide, saccharin, 5,5‐dimethylhydantoin, 2‐nitroaniline, 4‐nitroaniline, benzophenon hydrazine, and anthranilic acid led to the formation of phosphonato esters in high yield. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:630–639, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20725     

Labile Interactions in Aza‐aromatic Base Adducts of Lead(II) Thenoyltrifluoroacetonate

The polymeric form of lead(II) thenoyltrifluoroacetonate, [Pb(ttfa)₂], is modified by adduct formation with 2,2′‐bipyridine (bipy) and 1,10‐phenanthroline (phen) to give, in both cases, dimeric species [Pb₂(bipy)₂(ttfa)₄] and [Pb₂(phen)₂(ttfa)₄], respectively. Crystal structure determinations indicate that labile interactions involving the fluorine atoms and both the thenoyl and aza‐aromatic moieties may be important in determining the lattice arrays of these dimers, which are very similar, even though the dominant lattice forces may differ.     

Synthesis and Crystal Structure of [Pb(phe)2]n: a 2D Coordination Polymer of Lead(II) Containing Phenylalanine

[Pb(phe)₂]_n ( 1 ) (phe is the abbreviation ofphenylalanine) have been synthesized and characterized by elemental analyses, IR and ¹H NMR spectroscopy. The single crystal structure of 1 show the complex to be a 2D chain polymer as a result of phenylalanine bridging. Coordination number of Pb^II ions is six, PbN₂O₄, with “stereo‐chemically active” electron lone pairs, and the coordination sphere is hemidirected. To the best of our knowledge, this 2D coordination polymer is the first amino acid lead(II) complex that characterized by X‐ray structural analysis.