K4[PbSe4]⋅en⋅NH3: A Non‐Oxide,Non‐Halide Inorganic Lead(IV) Compound

The first inorganic lead(IV) compound without oxygen, nitrogen or halogen ligands attached to the lead atom was obtained as the potassium salt of the tetraselenidoplumbate(IV) anion [Pb^IVSe₄]^4?. It is stable under inert conditions which may enable the transfer of the chemistry of chalcogenidogermanate(IV) or chalcogenidostannate(IV) materials, to the lead homologues.     

Uncertainty measurement for automated macro program-processed quantitative proton NMR spectra

The evaluation of a fully automated quantitative proton nuclear magnetic resonance spectroscopy (qNMR) processing program, including the determination of its processing uncertainty, and the calculations of the combined uncertainty of the qNMR result, is presented with details on the use of a trimmed purity average. Quantitative NMR spectra (1359) were collected over a 4-month period on various concentrations of pseudoephedrine HCl dissolved in D₂O (0.0610 to 93.60 mg/mL) containing maleic acid (the internal standard) to yield signal-to-noise ratios ranging from 3 to 72,000 for analyte integral regions. The resulting 5436 purities exhibited a normal distribution about the best estimate of the true value. The median absolute deviation (MAD) statistical method was used to obtain a model of uncertainty relative to the signal-to-noise of the analyte’s integral peaks. The model was then tested using different concentrations of known purity chloroquine diphosphate. qNMR results of numerous illicit heroin HCl samples were compared to those obtained by capillary electrophoresis. Graphical Abstract

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Extending N-heterocyclic carbene ligands into the third dimension: a new type of hybrid phosphazane/NHC system

A simple, “click” synthetic approach to a new type of hybrid phosph(III)azane/NHC system is described. The presence of the phosphazane P₂N₂ ring unit, with P atoms flanking the NCN fragment and with this ring perpendicular to the binding site of the NHC, provides unique opportunities for modifying the electronic and steric character of these carbenes.     

Reactive matrix clean-up of naturally occurring perylene in young lignite

Young lignite from two locations in Sendai City, Japan, were analyzed for polynuclear aromatic compounds (PACs). Lignite samples were extracted with toluene and PACs were isolated by a compound-class-selective, reactive matrix clean-up. This clean-up separates all compounds of polynuclear aromatic structure, for example hydrocarbons and ketones and their primary metabolites, from interfering organic compounds. The result of this isolation procedure is, therefore, a group of a large number of polycyclic compounds with different functional groups. Further analysis is done by glass capillary gas chromatography. Perylene was identified as the only compound obtained by the reactive matrix clean-up of lignite samples from both locations. Concentrations were in the range of 1–10 mg kg⁻¹. Conversely, PACs resulting from particulate emissions from fossil fuel combustion always contain isomeric PAHs (polynuclear aromatic hydrocarbons) with some polycyclic aromatic ketones and thousands of primary and secondary metabolites at very low concentrations. This was demonstrated for a sample of urban air particulate matter, which is the source of PAC contamination of surface soil. The absence of accompanying PAHs and polynuclear aromatic ketones in the lignite samples confirms that perylene did not originate from a combustion process. It is assumed that the high concentrations of perylene are the result of a reduction of perylene quinone. Thus, the high perylene content of the lignite samples investigated is of biogenic origin.     

Postsynthesis racemization and place exchange reactions. Another step to unravel the origin of chirality for chiral ligand-capped gold nanoparticles

We examine how postsynthesis nanoparticle ligand shell modifications as a general approach can help in the understanding of currently proposed mechanisms for gold nanoparticle chirality. We compare the CD response of chirally decorated mixed-monolayer-protected gold nanoparticles synthesized in situ with quasi-identical gold nanoparticles either prepared by place exchange reactions or subjected to an aqueous base, resulting in partial hydrolysis and simultaneous partial racemization. We find that the CD response at wavelengths where the free chiral ligand does not absorb strongly depends on the preparation conditions, i.e., in situ synthesis vs place exchange, and that postsynthesis racemization of the chiral ligand produces racemic nanoparticles with no CD response, i.e., no induction of a chiral bias during reductive nanoparticle formation. Considering all experimental results for the described gold nanoparticle system with a C12H24 spacer between the nanoparticle surface and chiral center, the so-called "vicinal effect" with the formation of a supramolecular assembly of the chiral moieties seems to be active. Finally, we argue that postsynthesis nanoparticle ligand shell modifications such as racemization and/or place exchange reactions are very powerful tools to unravel contributions of the different gold nanoparticle chirality mechanisms.