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Isomeric Column‐Forming Esters and Imides with Varying Curvatures of the Aromatic Plane
Author(s) -
Ferreira Marli,
Moreira Thamires S.,
Cristiano Rodrigo,
Gallardo Hugo,
Bentaleb Ahmed,
Dechambenoit Pierre,
Hillard Elizabeth A.,
Durola Fabien,
Bock Harald
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201705084
Subject(s) - imide , chemistry , alkyl , crystallography , stacking , structural isomer , triphenylene , photochemistry , stereochemistry , polymer chemistry , organic chemistry , molecule
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 bis‐ ortho 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.