期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 24, 期 9, 页码 2214-2223出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201705084
关键词
chromophores; cyclization; electron-deficient compounds; liquid crystals; stacking interactions
资金
- Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior-Comite Francais d'Evaluation de la Cooperation Universitaire et Scientifique avec le Bresil (CAPES-COFECUB) [Ph-C 803-14]
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.
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