Anion-templated assembly of pseudorotaxanes: importance of anion template, strength of ion-pair thread association, and macrocycle ring size

A wide range of pseudorotaxane assemblies containing positively charged pyridinium, pyridinium nicotinamide, imidazolium, benzimidazolium and guanidinium threading components, and macrocyclic isophthalamide polyether ligands have been prepared using a general anion templation procedure. In noncompetitive solvent media, coupling halide anion recognition by a macrocyclic ligand with ion-pairing between the halide anion and a strongly associated cation provides the driving force for interpenetration. Extensive solution 1H NMR binding studies, thermodynamic investigations, and single-crystal X-ray structure determinations reveal that the nature of the halide anion template, strength of the ion-pairing between the anion template and the cationic threading component, and to a lesser extent favorable second sphere pi-pi aromatic stacking interactions between the positively charged threading component and macrocyclic ligand, together with macrocyclic ring size, affect the efficacy of pseudorotaxane formation.     

Design of optimal configuration for generating A0 Lamb mode in a composite plate using piezoceramic transducers

This work concerned a technique for a health monitoring system based on the generation and sensing of Lamb waves in composite structures by thin surface-bonded piezoceramic transducers. The objective was to develop transducers that are adapted for the damage detection in orthotropic composites. The key problem with the investigated Lamb waves was to select a mode to be sensitive to the damage. A hybrid modeling technique was therefore used to conceive transducers that were adapted to achieve such a feature. This modeling technique enabled studying the influence of the transducer characteristics on the Lamb waves propagating in orthotropic plates. It was demonstrated that a Lamb mode could be generated dominantly to other modes by using a multi-element transducer. The effectiveness of this technique was successfully verified experimentally on composite plates. It was shown that the dominant Lamb mode, obtained by use of dual-element transducers, was an appropriate mode for successfully detecting a damage in composites.     

Crystal and molecular structure of diphenylphosphinylacetic acid

Diphenylphosphinylacetic acid crystallizes in the monoclinic space groupP2_l/n with unit cell dimensionsa=5.6875(7),b=17.049(4),c=13.471(2) Å, =93.36(1)° and Z=4. The molecular packing consists of hydrogen bonded chains arising from intermolecular interactions between a carboxylic acid hydroxyl group and an oxygen of an adjacent phosphine oxide moiety.     

Quantification of small molecules in plasma with direct analysis in real time tandem mass spectrometry, without sample preparation and liquid chromatographic separation

Recently, a new ion source, Direct Analysis in Real Time (DART), has been introduced which allows direct biological sample introduction into a mass spectrometry (MS) system. The elimination of conventionally required sample preparation and separation by high-performance liquid chromatography (HPLC) prior to MS analysis represents a remarkable opportunity to reduce assay turn-around time, environmental impact and capital/manpower investment. This new technology initially was used in various qualitative applications to directly detect chemicals on solid surfaces, in liquids and gases. In this study, a DART source operating under ambient pressure with ground potential was installed onto a Sciex 4000 tandem mass spectrometer and employed in the sample analysis of plasma based on direct introduction into the DART-MS/MS system. Reasonable precision and accuracy (%CV and %Error, both <10%) were achieved of a significant number of compounds tested in biological fluids. In addition, the limit of detection for 80% of the tested compounds reached 5 ng/mL or lower which is sufficient for pharmaceutical drug discovery support. Finally, experimental conditions that significantly impacted assay performance were investigated with respect to optimization and limitation. Because of its simplicity, fast data acquisition (3-5 s) and low cost, DART has the potential to significantly impact quantitative pharmaceutical analysis in biological matrices.     

Tetrakis(imidazolium) macrocyclic receptors for anion binding

New (tetrakis)imidazolium macrocyclic receptor systems of variable cavity size have been synthesised by stepwise alkylation reactions of bis(imidazolium) precursor compounds. Proton NMR titration studies reveal the macrocycles to strongly bind halide and benzoate anions, with two receptor systems displaying notable selectivity for fluoride in competitive acetonitrile-water (9:1) solvent media.     

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New studies on the apparent allyl rotation in scorpion-like palladium complexes. The influence of non-directly bonded groups. X-ray molecular structures of [Pd(η-2-Me-C3H4)L]TfO, L=bpzmArOMe and bpz*mCy

New cationic 2-Me-allylpalladium complexes were prepared with the N,N-donor chelate ligands bis(pyrazol-1-yl)(R)methane (R=anisol-2-yl, bpzmArOMe; 2-hydroxyphenyl, bpzmArOH) and bis(3,5-dimethylpyrazol-1-yl)(R)methane (R=anisol-2-yl, bpz*mArOMe; cyclohexyl, bpz*mCy and ferrocenyl, bpz*mFc). The bpz′mR ligands adopt a rigid boat conformation after coordination to the Pd center and the R group is in the axial position of the metallacycle. The new complexes exhibit two isomeric forms in solution that differ in the relative orientation of the 2-Me-allyl group with respect to the bpz′mRPd fragment. The fluxional behavior of the new complexes, mainly in the context of the isomerization process, has been analyzed. Conclusions concerning the influence on this isomerization of the R group and the pyrazole substituents in positions 3 and 5 are discussed. The isomerization process was found to be affected by the presence of coordinating anions (Cl⁻) or by a change in the complex concentration. The molecular structures of the complexes [Pd(η³-2-Me-C₃H₄)(bpzmArOMe)]TfO and [Pd(η³-2-Me-C₃H₄)(bpz*mCy)]TfO have been determined by X-ray diffraction studies.