Rigidified merocyanine dyes with different aspect ratios: Dichroism and photostability
摘要:
A series of new rigidified merocyanines were investigated with regard to their optical properties as dichroic dyes. Guest/host-mixtures of the dyes were prepared using a liquid crystal and a reactive mesogen mixture. Their dichroism was studied using linearly-polarized UV/Vis-spectroscopy. A strong dependence of the dichroic ratio on the aspect ratio, the number of double bonds in the molecular structure, and on the maximum wavelength of absorption was found. A strategy to increase the aspect ratio has also been demonstrated. Additionally, the photostability was characterized using continued irradiation with polychromatic light from a xenon source. High photostability was found in all host mixtures in the absence of oxygen by alignment in a matrix. The suitability for their application as dichroic dyes in thin layer polarizers and guest/host-displays is herein discussed. (C) 2015 Elsevier Ltd. All rights reserved.
An efficient method for <i>retro</i>-Claisen-type C–C bond cleavage of diketones with tropylium catalyst
作者:M. A. Hussein、V. T. Huynh、R. Hommelsheim、R. M. Koenigs、T. V. Nguyen
DOI:10.1039/c8cc07329e
日期:——
cleavage in this reaction is usually promoted by a number of transition-metal Lewis acid catalysts or organic Brønsted acids/bases. Herein we report a new convenient and efficient method utilizing the tropylium ion as a mild and environmentally friendly organocatalyst to mediate retro-Claisen-type reactions. Using this method, a range of synthetically valuable substances can be accessed via solvolysis of
Intermolecular Multiple Dehydrogenative Cross‐Couplings of Ketones with Boronic Acids and Amines via Copper Catalysis
作者:Tianzhang Wang、Guowei Chen、Yu‐Jing Lu、Qian Chen、Yanping Huo、Xianwei Li
DOI:10.1002/adsc.201900419
日期:2019.8.21
versatile oxidative coupling reaction was developed for the synthesis of valuable β‐functionalized unsaturatedketones and meta‐substituted phenols. In the case of intramolecular reactions, achieving rapid molecular complexity through multiple dehydrogenative couplings is already a well‐established strategy. Herein, we report an intermolecular multiple dehydrogenative coupling between ketones and nucleophilic
Synthesis, spectral and structural characterization of cobalt(III) dithiocarbamato complexes: Catalytic application for the solvent free enamination reaction
using 1–2 mol% of the above cobalt(III) complexes as catalysts and these have been characterized by NMR, GC–MS and X-ray crystallography. Complexes 1, 2 and 3 are stabilized by intermolecular C–H⋯S interactions, leading to the formation of supramolecular architectures. Thermogravimetric analysis of complexes 1 and 2 have been investigated by TG-DTA, which indicate that cobalt sulfide is formed as the
series of rigidified tri-, penta- and heptamethine merocyaninedyes were synthesised. A piperidyl moiety was chosen as the electron-donating substituent while the electron-accepting group was varied from ketones to malononitriles and cyanoacetates. The structures of the compounds in the solid state and in solution were elucidated by X-ray diffraction and NMR spectroscopy, respectively, while optical properties
We have developed an iron-catalyzed direct olefination for enaminone synthesis, with saturated ketones as a source of olefins. This direct ketone β-functionalization reaction has readily available starting materials and a wide range of substrates and requires mild reaction conditions.