Pyrene‐Functionalised,Alternating Copolyimide for Sensing Nitroaromatic Compounds

A novel, pyrene‐functionalised copolymer has been synthesised in a single step via imidisation of poly(maleic anhydride‐alt‐1‐octadecene) with 1‐pyrenemethylamine, and its potential for the detection of volatile nitro aromatic compounds (NACs) evaluated. The new copolymer forms complexes in solution with NACs such as 2,5‐dinitrobenzonitrile, as shown by ¹H NMR, UV‐vis and fluorescence spectroscopy. Moreover, thin films of this copolymer, cast from THF solution, undergo almost instantaneous fluorescence quenching when exposed to the vapour of 2,5‐dinitrobenzonitrile (a model for TNT) at ambient temperatures and pressures.

     

Csp-tellurium copper cross-coupling: synthesis of alkynyl tellurides a novel class of antidepressive-like compounds

We present here the results on the synthesis of functionalized alkynyl tellurides using the reaction of vinyl, alkynyl, and aryl tellurides with several alkynyl iodides catalyzed by copper iodide. The reaction proceeded cleanly under mild reaction conditions, at room temperature, in the absence of base and ligand giving alkynyl tellurides in acceptable yields. The obtained compounds 3a-c and 3m-o were screened for antidepressive-like activity using the tail suspension test (TST) in mice. Compounds 3a-c and 3m-o administered at 10 mg/kg by oral route produced a significant antidepressant-like effect on the TST in mice.     

Incorporation of hexafluorobutyne into furans or phenols via reaction with iron(0) carbene or vinylketene complexes

Reaction of iron(0) carbene complexes with hexafluorobut-2-yne produces 3,4-bis(trifluoromethylated)furans in a process that is favored for electron-rich carbenes. No traces of furannulation or benzannulation are observed with Group 6 Fischer carbenes. Reaction of hexafluorobut-2-yne with a vinylketene iron(0) complex gives a 2,3-bis-trifluoromethylated phenol.     

Use of Tetradentate Monoanionic Ligands for Stabilizing Reactive Metal Complexes

Ligand scaffolding : The chemist's ability to choose from a wide range of supporting ligands is an important factor in designing new metal complexes. The introduction of new ligand scaffolds with different donor types and coordination numbers allows for the expansion of reaction chemistry at metal centers. This article surveys the use of the tetradentate monoanionic (TMDA) ligands (shown here) with main‐group, transition‐metal, and f‐block elements.

     

Photoinitiation rate profiles during polymerization of a dimethacrylate-based resin photoinitiated with camphorquinone/amine. Influence of initiator photobleaching rate

The photodecomposition of camphorquinone (CQ)/amine during the photo polymerization of a dimethacrylate-based resin under continuous irradiation was investigated in thick samples. The global CQ photoconsumption was measured by monitoring the decrease in light absorption as a function of irradiation time and the kinetics were satisfactory fitted to a first order expression where the rate constant of photobleaching was proportional to the irradiation intensity. In a thick sample, the photobleaching of the photoinitiator is accompanied by a deeper penetration of the light through the underlying layers. These gradients of photoinitiator concentration, light intensity and photoinitiation rate along the path of irradiation were calculated. The photodecomposition reaction was spatially inhomogeneous and the degree of nonuniformity increased with increased initial sample absorbance. The influence of the photobleaching process on the polymerization reaction was examined. The photobleaching rate of CQ was much slower than the polymerization rate and only 20% of the initial amount of CQ was consumed before the polymerization reaction had almost ceased. Results obtained in this research highlight the inherent interlinking of light attenuation and photobleaching rate in bulk polymerizing systems.     

A Thermally and Hydrolytically Stable Microporous Framework Exhibiting Single‐Chain Magnetism: Structure and Properties of [Co2(H0.67bdt)3]⋅20 H2O

Fixing a hole : Hydrothermal chemistry has been exploited in the preparation of a 3D framework material exhibiting 48 % accessible void volume and 1.5 % hydrogen uptake by weight at 120 kPa (see picture). The title compound also exhibits single‐chain magnetic behavior and reversible changes in magnetic properties upon solvation and desolvation.

     

The inverse inertia problem for graphs: Cut vertices, trees, and a counterexample

Let G be an undirected graph on n vertices and let S(G) be the set of all real symmetric n×n matrices whose nonzero off-diagonal entries occur in exactly the positions corresponding to the edges of G. The inverse inertia problem for G asks which inertias can be attained by a matrix in S(G). We give a complete answer to this question for trees in terms of a new family of graph parameters, the maximal disconnection numbers of a graph. We also give a formula for the inertia set of a graph with a cut vertex in terms of inertia sets of proper subgraphs. Finally, we give an example of a graph that is not inertia-balanced, which settles an open problem from the October 2006 AIM Workshop on Spectra of Families of Matrices described by Graphs, Digraphs and Sign Patterns. We also determine some restrictions on the inertia set of any graph.     

On the origin of the unique properties of supported Au nanoparticles

The unique catalytic activity of supported Au nanoparticles has been ascribed to various effects including thickness/shape, the metal oxidation state, and support effects. Previously, we reported the synthesis of ordered Au monolayers and bilayers on TiO(x), with the latter being significantly more active for CO oxidation than the former. In the present study, the electronic and chemical properties of ordered monolayer and bilayer Au films have been characterized by infrared reflection adsorption spectroscopy using CO as a probe and ultraviolet photoemission spectroscopy. The Au overlayers are found to be electron-rich and to have significantly different electronic properties compared with bulk Au. The common structural features of ordered Au bilayers and Au bilayer nanoparticles on TiO2(110) are described, and the exceptionally high catalytic activity of the Au bilayer structure related to its unique electronic properties.     

Analysis of volatiles and semivolatiles in drinking water by microextraction and thermal desorption

A new technique to analyze aqueous samples for nanograms per liter levels of volatile and semivolatile compounds using microextraction and thermal desorption into a gas chromatograph/ion trap mass spectrometer (GC/MS) is described. This method is inherently sensitive (50 mL of aqueous sample is extracted prior to each desorption), uses no solvents, and detects volatiles and semivolatiles in the same analysis. Aqueous standards and environmental samples are pumped through a length of porous-layer open-tubular capillary column, which is then thermally desorbed onto a 30 m × 0.25 mm i.d. analytical column interfaced to an ion trap mass spectrometer for subsequent separation and detection. Sharp chromatographic peaks and reproducible retention times (RT) were observed. Replicate injections of surrogates (n = 6) averaged 32.6% R.S.D. Analysis of domestic tap water detected 55 analytes, some at the low-nanograms per liter level, and detected 3 halogenated ethenes, not previously reported in drinking water. Analysis of an aqueous sample from a municipal ground water source detected the presence of numerous semivolatile compounds at trace-levels.     

Determination of the preferred conformation of the bicyclic Galerucella pheromone using density functional theory optimization and calculations of chemical shifts

A pheromone from the beetle, Galerucella calmariensis, was recently isolated and identified (Bartelt, R. J. et al. J. Chem. Ecol. 2006, 32, 693-712) as a 14-carbon, bicyclic dimethylfuran lactone, with the systematic name 12,13-dimethyl-5,14-dioxabicyclo[9.2.1]tetradeca-1(13),11-dien-4-one. The main 12-membered lactone ring is very flexible; as a result, there exist multiple possible conformations. The preferred conformation cannot be deduced solely from room-temperature NMR measurements. Using density functional (DFT) studies, 26 unique conformers with energies within 10.0 kcal/mol of the global minimum-energy structure were found. A mirror-image plane exists so that each conformer has an "inverse" structure with the same energy, for which the dihedral angles around the flexible ring have opposite sign. The isotropic 1H and 13C NMR chemical shifts of the DFT-optimized structures were calculated using the gauge-including atomic orbital (GIAO) method. By considering the relative energies of the conformers and the calculated and observed NMR spectra, we concluded that the molecule exists primarily as a mixture of two distinct conformers at room temperature, each being present with its mirror-image inverse. Structural interconversions among these likely occur on a time scale that is fast compared to the NMR experiments. Using mode-following and dihedral-driving techniques, several potential pathways were found for the conversion of the lowest-energy conformer to its mirror-image structure. Ab initio molecular dynamics (AIMD) using the 4-31G basis set was carried out for 50 ps to test the availability of various low-energy minima and the transition states found from the searches noted above.