Ueber kolloide Blutlaugensalzlösungen

Zusammenfassung Man gelangt zu kolloiden Systemen von Ferrozyankali durch Behandeln des festen Salzes mit Mischungen von Wasser+Aethyl-, Methyl-, Propylalkohol, Azeton usw., z. B. durch Schütteln von 0,1 g Salz mit 100 ccm Alkohol+ 50 ccm Wasser.     

4‐hydroxy‐6‐methyl‐3‐(5‐phenyl‐2E,4E‐pentadien‐1‐oyl)‐2H‐pyran‐2‐one: Synthesis and reactivity with amines

The synthesis and reactivity studies of 4‐hydroxy‐6‐methyl‐3‐(5‐phenyl‐2E,4E‐pentadien‐1‐oyl)‐2H‐pyran‐2‐one 2 with nucleophiles are reported. Reactions of 2 with hydrazine derivatives gave new pyrazole‐type com pounds while the reaction with ortho‐phenylenediamines yielded 1,5‐benzodiazepines. The reaction of 2 with ethylamine implies the 2H‐pyran‐2‐one ring opening and the formation of a strong conjugated compound 3.     

Redox‐Switchable Supramolecular Graft Polymer Formation via Ferrocene–Cyclodextrin Assembly

The redox switchable formation of very well‐defined supramolecular graft polymers in aqueous solution driven by host–guest interactions between ferrocene (Fc) and cyclodextrin (CD) is presented. The Fc‐containing acrylic backbone copolymer (PDMA‐stat‐Fc) is prepared via reversible addition–fragmentation chain transfer (RAFT) copolymerization of N,N‐dimethyl­acrylamide (DMA) and the novel monomer N‐(ferrocenoylmethyl)acrylamide (NFMA). Via the RAFT process, copolymers containing variable Fc ratios (5‐10 mol%) are prepared, affording polymers of molecular masses of close to 11 000 g mol⁻¹ and molar mass dispersities (Đ) of 1.2. The β‐cyclodextrin (β‐CD) containing building block is synthesized via RAFT‐polymerization, too, in order to afford a polymer with well‐defined molecular mass and low dispersity ( = 10 300 g mol⁻¹, Đ = 1.1), employing a propargyl‐functionalized chain transfer agent for the polymerization of N,N‐diethylacrylamide (DEA). The polymerization product is subsequently terminated with β‐CD via the regiospecific copper (I)‐catalyzed 1,3‐cycloaddition (PDEA‐βCD). Host–guest interactions between Fc and CD lead to the formation of supramolecular graft‐polymers, verified via nuclear Overhauser enhancement spectroscopy (NOESY). Importantly, their redox‐responsive character is clearly confirmed via cyclic voltammetry (CV). The self‐assembly of the statistical Fc‐containing lateral polymer chain in aqueous solution leads to mono‐ and multi‐core micelle‐aggregates evidenced via TEM. Only diffused cloud‐like, non‐spherical nanostructures are observed after addition of PDEA‐βCD (TEM).

     

Preparation of Photoactive Polymers and Postmodification via Nitroxide Trapping Under UV Irradiation

New types of photoactive homo and block copolymers bearing α−hydroxyalkylphenylketone (2‐hydroxy‐2‐methyl‐1‐phenylpropan‐1‐one) moieties as backbone substituents are prepared using nitroxide‐mediated radical polymerization (NMP). Such polymers can be readily activated via the Norrish‐type I photoreaction to give polymeric acyl radicals. Photolysis in the presence of a persistent nitroxide, which serves as a C‐ radical trapping reagent, leads to chemically modified polymers conjugated with nitroxide moieties. The number‐average molecular weight (M _n) of the prepolymers and the chemically modified polymers was determined by gel permeation chromatography (GPC). Structures were further confirmed by NMR spectroscopy and by attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy.     

Aromatic nitro substitution reaction between 4‐nitro‐N‐n‐butyl‐1,8‐naphthalimide and n‐heptanethiol in water–methanol binary mixtures

The second‐order rate constants of thiolysis by n‐heptanethiol on 4‐nitro‐N‐n‐butyl‐1,8‐naphthalimide (4NBN) are strongly affected by the water–methanol binary mixture composition reaching its maximum at around 50% mole fraction. In parallel solvent effects on 4NBN absorption molar extinction coefficient also shows a maximum at this composition region. From the spectroscopic study of reactant and product and the known H‐bond capacity of the mixture a rationalization that involves specific solvent H‐donor interaction with the nitro group is proposed to explain the kinetic data. Present findings also show a convenient methodology to obtain strongly fluorescent imides, valuable for peptide and analogs labeling as well as for thio‐naphthalimide derivatives preparations. Copyright © 2008 John Wiley & Sons, Ltd.     

Stimulated four-photon mixing and efficient polychromatic visible light generation in SiO2-based single-mode optical fibers pumped at 1.319 μm

The generation of near-infrared and intense visible light through stimulated multi-wave mixing processes in single-mode silica-based optical fibers pumped by a Q-switched and mode-locked Nd:YAG laser operated at 1.319 μm is described. The experimental results show that intense infrared light around 1.2 μm is produced via selp-hase-matched four-photon mixing at the minimum group velocity dispersion region of pure SiO₂-core and P₂O₅-doped silica fibers. In the visible spectral region, from 580 nm to 600 nm, 20 W peak power 100-ps pulses were generated by pumping single spans of single-mode P₂O₅-doped and undoped SiO₂-core fibers with 1.319-μm laser pulses. The signal light generated in such fibers propagated in the LP₀₂ fiber mode and exhibited a threshold power that depended upon the fiber length and a critical length that was power dependent. Also, it exhibited an asymmetrical spectrum of a few nanometers bandwidth, with a long tail toward high frequencies. For GeO₂-doped silica-based fibers, a multiple-wavelength visible signal propagating in several high-order fiber modes was generated.