Consequences of the ‘Pedersen papers’ on crown type chemistry at Würzburg and Bonn Universities: From heteroaromatic crowns and podands to large molecular and crystalline cavities including multisite receptors,cascade molecules,chromoionophores, siderophores,surfactant-type,and extreme ligands

We thank the editors of this issue for the opportunity to present the historic development of crown chemistry at the Universities of Wurzburg and Bonn in memory of C. J. Pedersen, the originator of the crown ethers. His legacy of science has tremendously stimulated research at both universities.This paper is dedicated to the memory of the late Dr C. J. Pedersen.     

Complex forming and extraction properties of oligo benzo-fused crown ethers

The complex forming properties with alkali metal and ammonium ions of a series of oligo benzo-condensed 18-crown-6 ethers1–8 having a different gradation of lipophilicity and of molecular rigidity are investigated by voltammetry at the interface of two immiscible electrolyte solutions (ITIES) and by a liquid-liquid extraction technique. The experimental results obtained in the two phase system H₂O/nitrobenzene are discussed in relation to the structure of the crown and the cation type. The stability constants for the 1 : 1 complexes of Na⁺, K⁺, Rb⁺, Cs⁺ and NH ₄ ⁺ in nitrobenzene have been determined and compared with the extraction constants for the 1: 1 complexes of Na⁺ and K⁺ and for the 1 : 1 and 1 : 2 complexes of Cs⁺, showing the effect of oligo benzo condensation for the 18-crown-6 system.     

AN INEXPENSIVE STIRRING DEVICE FOR THE 'MERRY-GO-ROUND' PHOTOREACTOR FOR THE DETERMINATION OF REACTION QUANTUM YIELDS

A simple bar magnet is employed to effect stirring of the contents of reaction cells in a'merry-go-round'photoreactor.     

Fast-response system for signal acquisition and processing in electrothermal atomic absorption spectrometry

An electrothermal atomic absorption (a.a.) spectrometer is modified to allow accurate correlation of absorbance and pyrometrically measured temperature with time. To by-pass the slow electronics of the spectrometer, the signal is fed from the preamplifier immediately after the photomultipier tube to a 12-bit A/D converter mounted in a 320K IBM-PC microcomputer. The wall temperature of the graphite furnace, measured with an automatic optical pyrometer, is recorded simultaneously with absorbance by feeding the pyrometer output to a second channel of the A/D board. Fast deuterium-arac background correction is also done. Background-corrected absorbance, background absorbance and temperature are recorded at 60 Hz. A simple algorithm allowed experimental activation energies to be calculated automatically. All programming was in BASIC or PASCAL.     

Photoionization of Naphthalene and Anthracene in Acetonitrile

Naphthalene and anthracene undergo a monophotonic ionization process in MeCN to produce the radical cations in low quantum yields (around 0.06 for anthracene). This reaction originates from the relaxed singlet excited state S₁, and it is not due to traces of H₂O in the solvent.     

Evidence for Multiple Binding Modes in the Initial Contact Between SARS-CoV-2 Spike S1 Protein and Cell Surface Glycans**

Infection of host cells by SARS-CoV-2 begins with recognition by the virus S (spike) protein of cell surface heparan sulfate (HS), tethering the virus to the extracellular matrix environment, and causing the subunit S1-RBD to undergo a conformational change into the ‘open’ conformation. These two events promote the binding of S1-RBD to the angiotensin converting enzyme 2 (ACE2) receptor, a preliminary step toward viral-cell membrane fusion. Combining ligand-based NMR spectroscopy with molecular dynamics, oligosaccharide analogues were used to explore the interactions between S1-RBD of SARS CoV-2 and HS, revealing several low-specificity binding modes and previously unidentified potential sites for the binding of extended HS polysaccharide chains. The evidence for multiple binding modes also suggest that highly specific inhibitors will not be optimal against protein S but, rather, diverse HS-based structures, characterized by high affinity and including multi-valent compounds, may be required.     

Photoelectron spectra of cyclopolysilanes

Summary He (I) PE spectra of cyclopentasilane and cyclohexasilane show excellent agreement with STO-3 G + ab initio calculations. The HOMO in both compounds is of (SiSi) 3 p character. First IP's appear at 9.4 and 9.6 eV respectively.

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Photoelektronenspektren von Cyclopolysilanen (Kurze Mitt.)

Zusammenfassung Die He (I) PE-Spektren der Cyclosilane Si₅H₁₀ und Si₆H₁₂ zeigen ausgezeichnete Übereinstimmung mit STO-3 G + ab initio Rechnungen. Beide Ringe besitzen HOMO's mit (SiSi) 3 p Charakter. Die ersten Ionisierungspotentiale liegen bei 9.4 bzw. 9.6 eV.

     

还原态Mo-Ni-K/C催化剂上CO加氢合成低碳混合醇

ＣＯ加氢合成低碳混合醇已成为Ｃ１化学的一个重要分支．目前用于这一过程的催化剂大都是改性的甲醇合成、ＦＴ合成或二者组合的催化剂．自从８０年代中期美国Ｄｏｗ化学品公司和联合碳化物公司首先发现ＭｏＳ２基催化剂具有优良的催化合成醇反应性能和良好的抗硫中毒能...     

Neue Wege zu Polysilanen

Summary Disilane derivatives undergo disproportionation reactions to polysilanes. Investigated were 1,2-dimethyldisilane and 1,2-dimethyltetrachlorodisilane with catalysts like NH₄Cl, AgCN, and Nacyanamide. In case of 1,2-dimethyldisilane, with more than catalytic amounts of NH₄Cl, a nitrogen containing polysilane is formed. Two new compoundsMeSiH(NCO)₂ andMe ₂Si₂(NCO)₄ were synthesized and characterized. The last one leads to a polymer at heating. Additionally an electrochemical formation of polydimethylsilane is described.