Exploring the Reactivity of a Frustrated Sn/P Lewis Pair: The Highly Selective Complexation of the cis-Azobenzene Photoisomer

The reactivity of the geminal frustrated Lewis pair (FLP) (F₅C₂)₃SnCH₂P(tBu)₂ ( 1 ) was explored by reacting it with a variety of small molecules (PhOCN, PhNCS, PhCCH, tBuCCH, H₃CC(O)CH=CH₂, Ph[C(O)]₂Ph, PhN=NPh and Me₃SiCHN₂), featuring polar or non-polar multiple bonds and/or represent α,β-unsaturated systems. While most adducts are formed readily, the binding of azobenzene requires UV-induced photoisomerization, which results in the highly selective complexation of cis-azobenzene. In the case of benzil, the reaction does not lead to the expected 1,2- or 1,4-addition products, but to the non-stereoselective (tBu)₂PCH₂-transfer to a prochiral keto function of benzil. All adducts of 1 were characterised by means of multinuclear NMR spectroscopy, elemental analyses and X-ray diffraction experiments.     

Three Short Stories about Hexaarylbenzene–Porphyrin Scaffolds

A feasible two‐step synthesis and characterization of a full series of hexaarylbenzene (HAB) substituted porphyrins and tetrabenzoporphyrins is presented. Key steps represent the microwave‐assisted porphyrin condensation and the statistical Diels–Alder reaction to the desired HAB‐porphyrins. Regarding their applications, they proved to be easily accessible and effective high molecular mass calibrants for (MA)LDI mass spectrometry. The free‐base and zinc(II) porphyrin systems, as well as the respective tetrabenzoporphyrins, demonstrate in solid state experiments strong red‐ and near‐infrared‐light emission and are potentially interesting for the application in “truly organic” light‐emitting devices. Lastly, they represent facile precursors to large polycyclic aromatic hydrocarbon (PAH) substituted porphyrins. We prepared the first tetra‐hexa‐peri‐hexabenzocoronene substituted porphyrin, which represents the largest prepared PAH‐porphyrin conjugate to date.     

Highly efficient water‐soluble visible light photoinitiators

The monoacylphosphineoxide (MAPO) salts Na‐TPO and Li‐TPO and the bisacylphosphineoxide (BAPO) salts BAPO‐ONa and BAPO‐OLi define an important and in the latter case a new class of water‐soluble photoinitiators (PIs) for radical polymerization. These compounds showed excellent water‐solubility of at least 29 g/L for Na‐TPO and up to 60 g/L for BAPO‐ONa in deionized water, thus exceeding the solubility of the state of the art PI for water‐based systems Irgacure 2959 ( I2959 ) 6‐ to 12‐fold. However, biocompatibility, storage stability, and reactivity were equally important to replace the state of the art compounds. Concerning these properties, the MAPO and BAPO salts were at least in the same range (biocompatibility, stability) or showed even better results (reactivity) and had the additional advantage of visible light initiation. Na‐TPO and Li‐TPO achieved double bond conversions of an aqueous solution of N‐acryloylmorpholine over 97% with broad band irradiation (320–500 nm), Li‐TPO showed additionally very good biocompatibility (LC₅₀ = 3.1 mmol/L) and BAPO‐OLi showed highest reactivity with visible light irradiation. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 473–479     

Growth, thermal stability and structure of ultrathin Zn-layers on Pd(1 1 1)

Low-energy ion scattering with monolayer sensitivity was applied to investigate ultrathin films of zinc on Pd(1?1?1). Uptake curves taken at 150?K indicate the simultaneous growth of multilayers with negligible interlayer transport. Annealing experiments for two-monolayer films reveal a rapid decrease in the zinc content on the surface layer at temperatures above 300?K, forming a metastable state with a Pd:Zn surface ratio of approx. 1:1 in the temperature region between 400 and 550?K. This state is most easily explained as a slightly buckled p(2?×?1)-PdZn surface alloy, with Zn atoms located approx. 0.25?? above their Pd counterparts.     

New Organosiloxanes Containing Silacycles

Abstract

The synthesis of carbon substituted 1, 1-dichloro- and l, l-bis(diethylamino)silacyclobutanes and butenes and their polycondensation reactions with bisphenol A, 1,2-ethanediol and 1,6-hexanediol is described. The monomer silacycles and the organosiloxane polymers are characterized by NMR (¹H-, ¹³C-, ²⁹Si-), GPC, DSC and elemental analysis.     

U6 is unsuitable for normalization of serum miRNA levels in patients with sepsis or liver fibrosis

MicroRNA (miRNA) levels in serum have recently emerged as potential novel biomarkers for various diseases. miRNAs are routinely measured by standard quantitative real-time PCR (qPCR); however, the high sensitivity of qPCR demands appropriate normalization to correct for nonbiological variation. Presently, RNU6B (U6) is used for data normalization of circulating miRNAs in many studies. However, it was suggested that serum levels of U6 themselves might differ between individuals. Therefore, no consensus has been reached on the best normalization strategy in ‘circulating miRNA''. We analyzed U6 levels as well as levels of spiked-in SV40-RNA in sera of 44 healthy volunteers, 203 intensive care unit patients and 64 patients with liver fibrosis. Levels of U6 demonstrated a high variability in sera of healthy donors, patients with critical illness and liver fibrosis. This high variability could also be confirmed in sera of mice after the cecal ligation and puncture procedure. Most importantly, levels of circulating U6 were significantly upregulated in sera of patients with critical illness and sepsis compared with controls and correlated with established markers of inflammation. In patients with liver fibrosis, U6 levels were significantly downregulated. In contrast, levels of spiked-in SV40 displayed a significantly higher stability both in human cohorts (healthy, critical illness, liver fibrosis) and in mice. Thus, we conclude that U6 levels in the serum are dysregulated in a disease-specific manner. Therefore, U6 should not be used for data normalization of circulating miRNAs in inflammatory diseases and previous studies using this approach should be interpreted with caution. Further studies are warranted to identify specific regulatory processes of U6 levels in sepsis and liver fibrosis.     

Speciation of gadolinium in surface water samples and plants by hydrophilic interaction chromatography hyphenated with inductively coupled plasma mass spectrometry

Hydrophilic interaction chromatography (HILIC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) was optimized for speciation analysis of gadolinium-based contrast agents in environmental samples, in particular surface river waters and plants. Surface water samples from the Teltow channel, near Berlin, were investigated over a distance of 5 km downstream from the influx of a wastewater treatment plant. The total concentration of gadolinium increased significantly from 50 to 990 ng?L^?1 due to the influx of the contrast agents. After complete mixing with the river water, the concentration remained constant over a distance of at least 4 km. Two main substances [Dotarem® (Gd-DOTA) and Gadovist® (Gd-BT-DO3A)] have been identified in the river water using standards. A gadolinium-based contrast agent, possibly Gd-DOTA (Dotarem®), was also detected in water plant samples taken from the Teltow channel. Therefore, uptake of contrast agents [Gadovist® (Gd-BTDO3A), Magnevist® (Gd-DTPA), Omniscan® (Gd-DTPA-BMA), Dotarem® (Gd-DOTA), and Multihance® (Gd-BOPTA)] by plants was investigated in a model experiment using Lepidium sativum (cress plants). HILIC–ICP-MS was used for identification of different contrast agents, and a first approach for quantification using aqueous standard solutions was tested. For speciation analysis, all investigated contrast agents could be extracted from the plant tissues with a recovery of about 54 % for Multihance® (Gd-BOPTA) up to 106 % for Gadovist® (Gd-BT-DO3A). These experiments demonstrate that all contrast agents investigated are transported from the roots to the leaves where the highest content was measured.     

Identification and characterization of individual airborne volcanic ash particles by Raman microspectroscopy

We present for the first time the Raman microspectroscopic identification and characterization of individual airborne volcanic ash (VA) particles. The particles were collected in April/May 2010 during research aircraft flights, which were performed by Deutsches Zentrum für Luft- und Raumfahrt in the airspace near the Eyjafjallajökull volcano eruption and over Europe (between Iceland and Southern Germany). In addition, aerosol particles were sampled by an Electrical Low Pressure Impactor in Munich, Germany. As references for the Raman analysis, we used the spectra of VA collected at the ground near the place of eruption, of mineral basaltic rock, and of different minerals from a database. We found significant differences in the spectra of VA and other aerosol particles (e.g., soot, nitrates, sulfates, and clay minerals), which allowed us to identify VA among other atmospheric particulate matter. Furthermore, while the airborne VA shows a characteristic Raman pattern (with broad band from ca. 200 to ca. 700 cm^?1 typical for SiO₂ glasses and additional bands of ferric minerals), the differences between the spectra of aged and fresh particles were observed, suggesting differences in their chemical composition and/or structure. We also analyzed similarities between Eyjafjallajökull VA particles collected at different sampling sites and compared the particles with a large variety of glassy and crystalline minerals. This was done by applying cluster analysis, in order to get information on the composition and structure of volcanic ash.