98027-84-0Relevant articles and documents
Synthetic, Optical and Theoretical Study of Alternating Ethylenedioxythiophene–Pyridine Oligomers: Evolution from Planar Conjugated to Helicoidal Structure towards a Chiral Configuration
Chevallier, Floris,Charlot, Marina,Mongin, Florence,Champagne, Beno?t,Franz, Edith,Clays, Koen,Blanchard-Desce, Mireille
, p. 4090 - 4101 (2016)
A series of alternating 3,4-ethylenedioxythiophene–alkynylpyridine oligomers (DA)n with increased solubility are synthesized and their photophysical properties and nonlinear optical properties are investigated. Their quadratic polarizabilities are determined from hyper-Rayleigh scattering experiments to obtain information on their conformations in solution. These chromophores, based on the alternation of electron-rich (D) and electron-deficient (A) moieties, exhibit optical properties that arise from the combination of dipolar and helicoidal features in the (DA)n homologue series where n=1–4. The transition from dipolar conjugated planar structures (n=1, 2) to helicoidal structures (n=3, 4) is clearly evidenced by results from symmetry-sensitive second-order nonlinear optical experiments. This suggests an approach towards highly efficient chiral chromophores for second-order nonlinear optics. Interestingly, this structural evolution also has significant impact on the photophysical properties: both absorption and fluorescence emission show bathochromic and hyperchromic shifts with increasing number of repeating units in the dipolar planar derivatives (n=1–2) but show saturation effects in the helicoidal structures (n=2–4). In addition, the helicoidal structures show sizeable two-photon absorption at 700–750 nm (40–100 GM) for compounds lacking either electron-donating or electron-withdrawing substituents.
Metathesis-active ligands enable a catalytic functional group metathesis between aroyl chlorides and aryl iodides
Lee, Yong Ho,Morandi, Bill
, p. 1016 - 1022 (2018/09/06)
Current methods for functional group interconversion have, for the most part, relied on relatively strong driving forces which often require highly reactive reagents to generate irreversibly a desired product in high yield and selectivity. These approaches generally prevent the use of the same catalytic strategy to perform the reverse reaction. Here we describe a catalytic functional group metathesis approach to interconvert, under CO-free conditions, two synthetically important classes of electrophiles that are often employed in the preparation of pharmaceuticals and agrochemicals—aroyl chlorides (ArCOCl) and aryl iodides (ArI). Our reaction design relies on the implementation of a key reversible ligand C–P bond cleavage event, which enables a non-innocent, metathesis-active phosphine ligand to mediate a rapid aryl group transfer between the two different electrophiles. Beyond enabling a practical and safer approach to the interconversion of ArCOCl and ArI, this type of ligand non-innocence provides a blueprint for the development of a broad range of functional group metathesis reactions employing synthetically relevant aryl electrophiles.
Synthesis and Structural Characterization of Ethynylene-Bridged Bisazines Featuring Various α-Substitution
Hübscher, J?rg,Seichter, Wilhelm,Gruber, Thomas,Kortus, Jens,Weber, Edwin
, p. 1062 - 1074 (2015/08/06)
A series of bispyridines and bispyrimidines 1a, 1b, 1c, 1d, 1e showing the heterocycles attached to both ends of an ethynylene unit and being α-substituted with chloro, tert-butylthio, and methoxy groups have been synthesized via cross-coupling technique and their crystal structures studied by X-ray diffraction analysis. Supramolecular interactions of C-H···N and π···π stacking type were found to largely dominate the structures according to the compound species. A trial was given to deduce the markedly differing temperatures of melting among the compounds from special features of the crystal structures.
