Solution-assisted assembly of organic semiconducting single crystals on surfaces with patterned wettability

Two efficient approaches to assembling organic semiconducting single crystals are described. The methods rely on solvent wetting and dewetting on substrates with patterned wettability to selectively direct the deposition or removal of organic crystals. Substrates were functionalized with different self-assembled monolayers (SAMs) to achieve the desired wettabilities. The assembly of different organic crystals over centimeter-squared areas on Au, SiO2, and flexible plastic substrates was demonstrated. By designing line features on the substrate, the alignment of crystals, such as CuPc needles, was also achieved. As a demonstration of the potential application of this assembly approach, arrays of single-crystal organic field-effect transistors were fabricated by patterning organic single crystals directly onto and between transistor source and drain electrodes.     

Determination of therapeutics with growth-hormone secretagogue activity in human urine for doping control purposes

The administration of growth-promoting agents such as human growth hormone as well as compounds with respective secretagogue activity is prohibited in sports according to the regulations of the World Anti-Doping Agency. Acetylcholine esterase inhibitors have been demonstrated to stimulate growth-hormone secretion in elderly humans, and new orally active drugs have been developed to provide alternatives to therapeutic injections of growth-hormone preparations. Preventive anti-doping strategies include method development for emerging drugs and potentially misused compounds. Hence, the mass spectrometric dissociation behavior of three acetylcholine esterase inhibitors (donepezil, galantamine and rivastigmine) and a structural analogue to the growth-hormone secretagogue SM-130686 were studied using high-resolution/high-accuracy orbitrap mass spectrometry. These data provided substantial information for screening procedures, complementing common methods of sports drug testing. Using liquid-liquid extraction and subsequent liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis, the four target analytes were determined at urinary concentrations of 15-20 ng/mL, recoveries ranged from 55-97%, and assay precisions were calculated at 5.2-15.8% (intraday) and 10.2-21.6% (interday) for all compounds. The applicability of the developed assay to authentic urine specimens was tested using two administration study urine samples after application of Reminyl (galantamine) and Aricept (donepezil). In both cases, the administered drug and the respective desmethylated metabolites were detected.     

A new dirhodium catalyst with hemilabile tropolonato ligands for C-H bond functionalization

Don't hold on too tightly! In a new dirhodium catalyst for C-H functionalization reactions, two tropolonato ligands are introduced as hemilabile chelating ligands (see scheme). Only two bridges hold the Rh-Rh core together. The tropolonato ligands can liberate a binding site in the equatorial coordination sphere of the catalyst. This opens a doorway to new mechanistic channels in C-H functionalization.     

Ca2Ga3MgN5 – A Highly Condensed Nitridogallate

The nitridogallate Ca₂Ga₃MgN₅ was obtained from reaction of the elements in sodium flux with Na‐azide at 760 °C in weld shut niobium ampoules. Crystal structure solution and refinement was carried out on the basis of single‐crystal X‐ray diffraction data. Ca₂Ga₃MgN₅ [space group C2/m (no. 12), a = 11.160(2), b = 3.2965(7), c = 8.006(2) Å, and β = 109.93(3)°, Z = 2] shows an anionic substructure made up of mixed (Mg/Ga)N₄ tetrahedra, which are sharing both common vertices and edges building a three‐dimensional network. The crystal structure of Ca₂Ga₃MgN₅ is related to known alkaline earth nitridosilicates (M^II₂Si₅N₈, M^II = Sr, Ba), but is significantly higher condensed due to additional edge‐sharing in the anionic substructure.     

Émilie du Châtelet (1706–1749) – ,,die Nachwelt wird Sie mit Erstaunen betrachten“

Zusammenfassung Mit diesem Beitrag wird an die Gelehrte émilie du Chatelet (1706–1749) erinnert, die vor 300 Jahren in Paris geboren wurde. Der Text soll Einblicke in ihr Leben und ihren wissenschaftlichen Kontext geben.émilie du Chatelet lernte und arbeitete mathematisch, naturphilosophisch und -wissenschaftlich zu einer Zeit, als Frauen von h?herer, wissenschaftlicher Bildung institutionell augeschlossen waren und es für Frauen als unschicklich galt, die eigene Gelehrsamkeit selbstbewu?t ?ffentlich zu zeigen.Trotz dieser Hindernisse, gelang es du Chatelet sich Kenntnisse anzueignen, die die der meisten ihrer Zeitgenossen bei weitem überragten. Sie schrieb naturwissenschaftliche Abhandlungen, verfa?te ein Physiklehrbuch und fertigte in ihren letzten Lebensjahren eine kommentierte übersetzung der Principia (1686) von Newton an. Mathematics Subject Classification (2000) 01-99     

Determination of 129I in large soil samples after alkaline wet disintegration

Summary Large soil samples (up to 500 g) can conveniently be disintegrated by hydrogen peroxide in an utility tank under alkaline conditions to determine subsequently ¹²⁹I by neutron activation analysis. Interfering elements such as Br are removed already before neutron irradiation to reduce the radiation exposure of the personnel. The precision of the method is <10% (1 RSD). The accuracy was checked by determining ¹²⁹I also by the combustion method.     

Studies on the Glycosylation of N-Acetylneuraminic Acid

Abstract

Glycal derivatives of N-acetylneuraminic acid were prepared and their N-iodosuccinimide-mediated glycosylation shown to proceed only with most reactive alcohols, Their reduced enol ether reactivity is attributed to the α unsaturated ester reature. Thus several reduced glycal derivatives were synthesized. These couid be glycosyiatec with simple alcohols as well as otner saccnarides as aglycones in averaae to modest yields with the trans-diaxiai additions compounas prevailing. A number or selective and specific prepparation led to both the anomeric phenylthioglycosides or N dcety Ineuraminic acid. These could be used in phenylmercurl triflate-promoted glycosylations to afford several derivatives.