78607-36-0Relevant 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 (2016/12/23)
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.
Deprotonation of chloropyridines using lithium magnesates
Awad, Ha?an,Mongin, Florence,Trécourt, Fran?ois,Quéguiner, Guy,Marsais, Francis
, p. 7873 - 7877 (2007/10/03)
Chloropyridines are deprotonated using lithium magnesates. 4-Chloropyridine was deprotonated on treatment with 1/3 equiv of the highly coordinated magnesate Bu3(TMP)MgLi2 in THF at -10°C, as evidenced by trapping with I2. The use of Bu(TMP)2MgLi in Et 2O allowed the reaction of 2-chloropyridine, giving the 3-functionalized derivative as the main product. Mixtures of 3- and 4-functionalized derivatives were obtained when 2,6-dichloropyridine was involved in the reaction. Performing the reaction on 3-chloropyridine with lithium magnesates in THF, either the 4,4′-dimer or the 4-iodo derivative was formed after quenching by I2, the former using 1/3 equiv of Bu2(TMP)MgLi and the latter using 1 equiv of (TMP)3MgLi. Similar results were observed with 3,5-dichloropyridine, 2,5-dichloropyridine and 3-chloro-2-fluoropyridine. 1,2-Migration of the lithium arylmagnesate formed by deprotonation was proposed to justify the dimers formation.
