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Article Dans Une Revue Chemistry - A European Journal Année : 2018

Isomeric Column-Forming Esters and Imides with Varying Curvatures of the Aromatic Plane

Résumé

Dibenzo[a,j]coronene-tetracarboxylic alkyl esters and imides with either a centrosymmetric bis-peri substitution pattern or a polar bis-ortho substitution pattern form hexagonal columnar mesophases, which in the case of the imides persist at room temperature. The bis-peri isomers are obtained via a two-fold oxidative photocyclization; the bisortho isomers are accessed via a glyoxylic Perkin reaction of triphenylene and naphthalene building blocks. Steric congestion between the substituents and the adjacent benzo protrusion in the bis-ortho esters and imides leads to bending of the aromatic plane, which thus avoids twisting. These isomers surprisingly show a more pronounced liquid crystalline behaviour than their non-bent bis-peri homologs, accommodating non-planarity with columnar order by slipped stacking. Whereas both types of ester and the bis-peri imide show an optical behaviour typical for perylene chromophores, the strongly bent bis-ortho imide distinguishes itself notably from them by its absorption spectrum. The electron acceptor strength of the isomeric diimides is found to differ, the hexagonal (peri) diimide having a 0.20 eV lower LUMO energy than the pentagonal (ortho) isomer.
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Dates et versions

hal-01705565 , version 1 (09-02-2018)

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Marli Ferreira, Thamires Moreira, Rodrigo Cristiano, Hugo Gallardo, Ahmed Bentaleb, et al.. Isomeric Column-Forming Esters and Imides with Varying Curvatures of the Aromatic Plane. Chemistry - A European Journal, 2018, 24 (9), pp.2214 - 2223. ⟨10.1002/chem.201705084⟩. ⟨hal-01705565⟩

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