Bimetallic assemblies, [Ni(en)2]3[M(CN)6]2·3H2O (en = H2NCH2CH2NH2; M = Fe,Co)

The reaction between tris(ethyl­enedi­amine)­nickel(II) cations and hexa­cyanometallate(III) anions (M = Fe, Co) yields ordered bimetallic assemblies, catena‐poly­[[tris­(ethyl­enedi­amine)­nickel‐bis(μ‐hexa­cyano­iron‐N,N′)] trihydrate] and catena‐poly­[[tris­(ethyl­enedi­amine)­nickel‐bis(μ‐hexa­cyano­cobalt‐N,N′)] trihydrate], [{Ni(C₂H₈N₂)₂}₃{M(CN)₆}₂]·3H₂O, in which both cis and trans [Ni(en)₂] and [M(CN)₆] moieties are linked to give S‐shaped Ni–NC–M–CN–Ni–NC–M–CN–Ni units which are cross­linked to give ribbons parallel to the b axis. The two compounds are isomorphous with mean metal–ligand distances Fe—C = 1.940 (3), Co—C = 1.844 (3) and Ni—N = 2.102 (2) Å for the iron, and 2.105 (3) Å for the cobalt compound. These compounds appear to be identical with those formulated as [Ni(en)₂]₃[M(CN)₆]₂·2H₂O [Ohba, Maruona, Okawa, Enoki & Latour (1994). J. Am. Chem. Soc. 116 , 11566–11567; Ohba, Fukita & Okawa (1997). J. Chem. Soc. Dalton Trans. pp. 1733–1737] which were indexed on a smaller unit cell and described as disordered.     

Small‐angle X‐ray scattering as a useful supplementary technique to determine molecular masses of polyelectrolytes in solution

Determination of molecular masses of charged polymers is often nontrivial and most methods have their drawbacks. For polyelectrolytes, a new possibility for the determination of number‐average molecular masses is represented by small‐angle X‐ray scattering (SAXS) which allows fast determinations with a 10% accuracy. This is done by relating the mass to the position of a characteristic peak feature which arises in SAXS due to the local ordering caused by charge‐repulsions between polyelectrolytes. Advantages of the technique are the simplicity of data analysis, the independency from polymer architecture, and the low sample and time consumption. The method was tested on polyelectrolytes of various structures and chemical compositions, and the results were compared with those obtained from more conventional techniques, such as asymmetric flow field‐flow fractionation, gel permeation chromatography, and classical SAXS data analysis, showing that the accuracy of the suggested method is similar to that of the other techniques. © 2016 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1913–1917     

Free-knot spline approximation of stochastic processes

We study optimal approximation of stochastic processes by polynomial splines with free knots. The number of free knots is either a priori fixed or may depend on the particular trajectory. For the s-fold integrated Wiener process as well as for scalar diffusion processes we determine the asymptotic behavior of the average L_p-distance to the splines spaces, as the (expected) number of free knots tends to infinity.     

Application of Partial Wave Crossing Relations to πN Scattering

The partial wave crossing relations derived in a recent paper by Steiner [1] are used for a calculation of the πN S-wave amplitudes in the region 8 ≦ s ≦ (M − 1)². The corresponding Argand diagrams show the pseudoresonance behaviour predicted in [1]. The results for the real parts are compared with an independent calculation using fixed-t dispersion relations.     

Mucin-Inspired Single-Chain Polymer (MIP) Fibers as Potent SARS-CoV-2 Inhibitors

Mucins are the key component of the defensive mucus barrier. They are extended fibers of very high molecular weight with diverse biological functions depending strongly on their specific structural parameters. Here, we present a mucin-inspired nanostructure, produced via a synthetic methodology to prepare methacrylate-based dendronized polysulfates ( MIP-1 ) on a multi gram-scale with high molecular weight (MW=450 kDa) and thiol end-functionalized mucin-inspired polymer ( MIP ) via RAFT polymerization. Cryo-electron tomography (Cryo-ET) analysis of MIP-1 confirmed a mucin-mimetic wormlike single-chain fiber structure (length=144±59 nm) in aqueous solution. This biocompatible fiber showed promising activity against SARS-CoV-2 and its mutant strain, with a remarkable low half maximal (IC₅₀) inhibitory concentration (IC₅₀=10.0 nM). Additionally, we investigate the impact of fiber length on SARS-CoV-2 inhibition by testing other functional polymers ( MIPs ) of varying fiber lengths.     

Schlenk's Legacy—Methyllithium Put under Close Scrutiny

Commercially available stock solutions of organolithium reagents are well-implemented tools in organic and organometallic chemistry. However, such solutions are inherently contaminated with lithium halide salts, which can complicate certain synthesis protocols and purification processes. Here, we report the isolation of chloride-free methyllithium employing K[N(SiMe₃)₂] as a halide-trapping reagent. The influence of distinct LiCl contaminations on the ⁷Li-NMR chemical shift is examined and their quantification demonstrated. The structural parameters of new chloride-free monomeric methyllithium complex [(Me₃TACN)LiCH₃], ligated by an azacrown ether, are assessed by comparison with a halide-contaminated variant and monomeric lithium chloride [(Me₃TACN)LiCl], further emphasizing the effect of halide impurities.     

Derivatives of 3′-Azidothymidine with 6-Cyanopyridone as Base or as Phosphoramidate Ester and their Antiretroviral Activity

Strongly pairing ethynylpyridone C-nucleosides are attractive surrogates for thymidine in oligonucleotides. Exploratory work on the antiviral activity of 3′-azidothymidine (AZT) derivatives with ethynylpyridone as base had identified strong lipophilicity as a limiting factor. Two strategies are being pursued to overcome this issue. In order to make the base more polar, the ethynyl group has been replaced with a cyano group, leading to a cyanopyridone C-nucleoside, whose eleven-step synthesis is reported here, together with the synthesis of a 3′-azido-2′,3′-dideoxynucleoside derivative. The base pairing with adenine in a DNA duplex was studied by UV melting analysis of a self-complementary hexamer containing the 6-cyano-2′-deoxynucleoside instead of thymidine. A melting point increase of 2 °C compared to the unmodified control was found. The other strategy employs a phosphoramidate prodrug design with less lipophilic amino acid esters. Here, anti-HIV test of the alaninyl and prolinyl methyl esters of AZT gave promising results in cell culture experiments, increasing the selectivity index up to 5.8-fold for the III_B strain and up to 5-fold for the ROD strain of the virus, as compared to the parent nucleoside. These findings help to design the next generation of pyridone C-nucleosides with potential applications as antivirals.