Base-catalyzed condensation of cyclopentadiene derivatives. Synthesis of fulvalene analogues: strong proaromatic electron acceptors

A series of proaromatic electron acceptors derived from fulvenes were synthesized from tetrachlorocyclopentadiene and previously unknown 1,4-dicyano- and 1,4-dialkoxycarbonyl-2,3-dimethoxy cyclopentadienes. Two reversible one-electron reductions steps observed for fulvalenes coalesce into one two-electron reduction step upon increasing the length of the conjugating bridge.     

Bismuth‐Based Coordination Polymers with Efficient Aggregation‐Induced Phosphorescence and Reversible Mechanochromic Luminescence

Two bismuth coordination polymers (CPs), (TBA)[BiBr₄(bp4mo)] (TBA=tetrabutylammonium) and [BiBr₃(bp4mo)₂], which are based on the rarely used simple ditopic ligand N‐oxide‐4,4′‐bipyridine (bp4mo), show mechanochromic luminescence (MCL). High solid‐state phosphorescence quantum yields of up to 85 % were determined for (TBA)[BiBr₄(bp4mo)] (λ_em=540 nm). Thorough investigations of the luminescence properties combined with DFT and TDDFT calculations revealed that the emission is due to aggregation‐induced phosphorescence (AIP). Upon grinding, both samples became amorphous, and their luminescence changed from yellow to orange and red, respectively. Heating or exposure to water vapor led to the recovery of the initial luminescence. These materials are the first examples of mechanochromic phosphors based on bismuth(III).     

Hydrotalcite-quinolinate composites as catalysts in a coupling reaction

Samples of layered double hydroxides were prepared by a sol–gel procedure. Quinolinate Al(C₉H₆NO)₃ units were added during the synthesis, leading to composite quinolinate hydrotalcite-like compounds. The amount of quinolinate was varied, showing that the number of organic building blocks determines the physicochemical properties of materials, which differ significantly from those commonly reported for hydrotalcites without any quinolinate. The order of layers, specific surface area and coordination of aluminium were the parameters most significantly influenced by the presence of the quinolinate as a part of the brucite-like layers. The composite quinolinate-hydrotalcite materials were tested to catalyse the Kabachnik–Fields reaction.

Open image in new window

Graphical abstract Adding of quinolinate Al(C₉H₆NO)₃ to hydrotalcite-like compounds creates disorder in the stack of brucite-like layers, leading to a significant modification of structural, textural and catalytic properties. The presence of quinolinate inhibits the enchainment of octahedral blocks in hydrotalcite but develop specific surface areas as high as 600 m²g^?1.

     

Effects of γ-irradiation on caprolactam level from multilayer PA-6 films for food packaging: Development and validation of a gas chromatographic method

A gas chromatographic method to determine caprolactam in multilayer PA-6 films used for meat foodstuffs and cheese was developed and validated. A wide linear range (0.8–400 μg/ml), RSD4.1% and recovery higher than 90.0% were obtained for the chromatographic system, while precision and accuracy of the method showed RSD3.8%, recovery from 95.5–100.0% and LOQ of 32 μg/g. Irradiated (3, 7 and 12 kGy) and non-irradiated commercial films were analyzed. Most of them increased caprolactam levels with the increase of irradiation doses.     

Synthetic strategies to derivatizable triphenylamines displaying high two-photon absorption

A versatile synthetic strategy to access a set of highly fluorescent pi-conjugated triphenylamines bearing a functional linker at various positions on one phenyl ring is described. These compounds were designed for large two-photon absorption (2PA) and in particular for labeling of biomolecules. The monoderivatized trisformylated or trisiodinated intermediates described herein allow introduction of a large variety of electron-withdrawing groups required for large 2PA as well as a panel of chemical functions suitable for coupling to biomolecules. The monoderivatized three-branched compounds and in particular the benzothiazole (TP-3Bz) series show remarkable linear (high extinction coefficients and high quantum yield) and nonlinear (high 2-photon cross sections) optical properties. Interestingly the presence of functional side chains does not disturb the two-photon absorption. Finally, monoderivatized two-branched derivatives also appear to be valuable candidates. Altogether the good optical properties of the new derivatizable pi-conjugated TPA combined with their small size and their compatibility with bioconjugation protocols suggest that they represent a new chemical class of labels potentially applicable for the tracking of biomolecules using two-photon scanning microscopy.     

A straightforward synthesis of 3-acylphospholes

[structure: see text] The reaction of 2,5-diphenylphospholide, first with acyl chlorides, then with tBuOK, provides a direct access to 3-acyl-2,5-diphenylphospholides via a 1H-, 2H-, 3H-phosphole equilibrium.     

Crystal engineering of pharmaceutical co-crystals from polymorphic active pharmaceutical ingredients

The carboxylic acid-primary amide supramolecular heterosynthon is exploited for the generation of pharmaceutical co-crystals that contain two active pharmaceutical ingredients that are polymorphic in their pure forms.     

Structuring sedimentation in a shear-thinning fluid

We study the sedimentation of suspensions of monodisperse non-Brownian particles in a shear-thinning polymeric fluid. We observe the formation of particle-rich structures and show that they are associated with a well-defined flow pattern. The results suggest that the observed structuring is a consequence of particle aggregation that amplifies concentration heterogeneities, the flow pattern being further driven by a gravitational instability.