Amphiphilic folded dendrimer discs and their thermosensitive self-assembly in water

Folded dendrimers with peripheral ether side chains show a thermally induced hierarchical aggregation process, in which the transition temperature and the dimensions of the aggregates can readily be tuned via the generation number (see figure).     

Heterobimetallic Cuprates Consisting of a Redox‐Switchable,Silicon‐Based Metalloligand: Synthesis,Structures, and Electronic Properties

A series of bimetallic silyl halido cuprates consisting of the new tripodal silicon‐based metalloligand [κ³N‐Si(3,5‐Me₂pz)₃Mo(CO)₃]^? is presented (pz=pyrazolyl). This metalloligand is straightforwardly accessible by reacting the ambidentate ligand tris(3,5‐dimethylpyrazolyl)silanide ({Si(3,5‐Me₂pz)₃}^?) with [Mo(CO)₃(η⁶‐toluene)]. The compound features a fac‐coordinated tripodal chelating ligand and an outward pointing, “free” pyramidal silyl donor, which is easily accessible for a secondary coordination to other metal centers. Several bimetallic silyl halido cuprates of the general formula [CuX{μ‐κ¹Si:κ³N‐Si(3,5‐Me₂pz)₃Mo(CO)₃}]^? (X=Cl, Br, I) have been synthesized. The electronic and structural properties of these complexes were probed in detail by X‐ray diffraction analysis, electrospray mass spectrometry, infrared‐induced multiphoton dissociation studies, cyclic voltammetry, spectroelectrochemistry, gas‐phase photoelectron spectroscopy, as well as UV/Vis and fluorescence spectroscopy. The heterobimetallic complexes contain linear two‐coordinate copper(I) entities with the shortest silicon–copper distances reported so far. Oxidation of the anionic complexes in methylene chloride and acetonitrile solutions at ${E{{0\hfill \atop 1/2\hfill}}}$ =?0.60 and ?0.44 V (vs. ferrocene/ferrocenium (Fc/Fc⁺)), respectively, shows substantial reversibility. Based on various results obtained from different characterization methods, as well as density functional theory calculations, these oxidation events were attributed to the Mo⁰/Mo^I redox couple.     

Towards the Core Structure of Strychnos Alkaloids Using Samarium Diiodide‐Induced Reactions of Indole Derivatives

This report describes the development of a first and second generation approach towards the synthesis of the ABCEG pentacyclic core structure of Strychnos alkaloids. First, we discuss a sequential approach applying a series of functional group transformations to prepare suitable precursors for cyclization reactions. These include attempts of samarium diiodide‐induced cyclizations or a Barbier‐type reaction of a transient lithium organyl, which successfully led to a tetracyclic key building block earlier used for the synthesis of strychnine. Secondly, we account our first steps towards the development of an atom‐economical samarium diiodide‐induced cascade reaction using “dimeric” indolyl ketones as cyclization precursors. In this context, we discuss plausible mechanisms for the samarium diiodide‐induced cascade reaction as well as transformations of the obtained tetracyclic dihydroindoline derivatives.     

QUANTIS: Data quality assessment tool by clustering analysis

Automatically generated kinetic networks are ideally validated against a large set of accurate, reproducible, and easy-to-model experimental data. However, although this might seem simple, it proves to be quite challenging. QUANTIS, a publicly available Python package, is specifically developed to evaluate both the precision and accuracy of experimental data and to ensure a uniform, quick processing, and storage strategy that enables automated comparison of developed kinetic models. The precision is investigated with two clustering techniques, PCA and t-SNE, whereas the accuracy is probed with checks for the conservation laws. First, the developed tool processes, evaluates, and stores experimental yield data automatically. All data belonging to a given experiment, both unprocessed and processed, are stored in the form of an HDF5 container. The demonstration of QUANTIS on three different pyrolysis cases showed that it can help in identifying and overcoming instabilities in experimental datasets, reduce mass and molar balance closure discrepancies, and, by evaluating the visualized correlation matrices, increase understanding in the underlying reaction pathways. Inclusion of all experimental data in the HDF5 file makes it possible to automate simulating the experiment with CHEMKIN. Because of the employed InChI string identifiers for molecules, it is possible to automate the comparison experiment/simulation. QUANTIS and the concepts demonstrated therein is a potentially useful tool for data quality assessment, kinetic model validation, and refinement.     

Application of the photoionization detector for the determination of ethanol in aqueous solutions and human breath

A determination of ethanol is described, which is based on a purging system in conjunction with a photoionization detector. With that system a fast and reliable determination of ethanol in aqueous solutions is possible. The system has been used for the analysis of wine. The 3-detection limit has been 0.005% ethanol, the relative standard deviation 4.8 to 6.0% and the time constant of the entire analytical system 20 s. The photoionization detector has been also applied to the analysis of artificial and genuine human breath. A comparison with gas-chromatography and non-dispersive IR-detection has been proven the reliability of results.     

Application of the photoionization detector for the determination of ethanol in aqueous solutions and human breath

A determination of ethanol is described, which is based on a purging system in conjunction with a photoionization detector. With that system a fast and reliable determination of ethanol in aqueous solutions is possible. The system has been used for the analysis of wine. The 3delta-detection limit has been 0.005% ethanol, the relative standard deviation 4.8 to 6.0% and the time constant of the entire analytical system 20 s. The photoionization detector has been also applied to the analysis of artificial and genuine human breath. A comparison with gas-chromatography and non-dispersive IR-detection has been proven the reliability of results.