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.
Mono‐ and diglyoxylation of chrysene and naphthalene leads to Perkin reactants that yield bismaleates, which efficiently photocyclize to elongated phenacenetetracarboxylic esters. Their band gaps remain significantly larger than the value postulated for polyphenacene. The reaction with α‐branched amines gives the corresponding imides, which are significantly stronger electron acceptors than the esters. The obtained [12]‐ and [14]phenacenes are the longest [n]phenacenes that have been synthesized to date.
Laterally decorated ribbon-shaped graphene segments made of twelve benzene units self-assemble into a nematic anisotropic glass at room temperature with high birefringence and polarized fluorescence.
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