From 1,4‐Phenylenebis(phenylmaleate) to a Room‐Temperature Liquid‐Crystalline Benzo[ghi]perylene Diimide

Abstract

The photocyclization of tetraethyl 1,4‐phenylenebis(phenylmaleate) in the presence of iodine and oxygen predominantly yields tetraethyl [5]helicene‐5,6,9,10‐tetracarboxylate, together with small amounts of tetraethyl dibenz[a,h]anthracene‐5,6,12,13‐tetracarboxylate and tetraethyl benzo[ghi]perylene‐3,4,11,12‐tetracarboxylate. The helicene tetraester is planarized to the benzoperylene tetraester by Scholl reaction with AlCl3 followed by reesterification of the partially hydrolyzed crude product. Subsequent treatment with a branched alkylamine yields a columnar liquid‐crystalline benzoperylene diimide whose mesophase is stable at room temperature despite its limited and non‐centrosymmetric alkyl periphery. Its absorption spectrum is markedly red‐shifted compared to that of a similar benzoperylene triimide.

Cyclic tris-[5]helicenes with single and triple twisted Möbius topologies and Möbius aromaticity

“…The cyclo -bis-[5]helicene 1 was expected not to exhibit any conjugation between its two parts due to a lack of coplanarity at the junctions between helicenes. This was confirmed by the absorption spectra, where this cyclic dimer of ester-substituted [5]helicenes behaved approximately like two independent ester-substituted [5]helicenes21 (Fig. 2).…”

Cyclobishelicenes: Shape‐Persistent Figure‐Eight Aromatic Molecules with Promising Chiroptical Properties

“…Racemic [5]helicene 6 was preparedb yt he same approach. [10] The discrimination of the enantiomerso f3b was first investigated by using NMR spectroscopy in chiral liquid crystals. [11] Indeed, because of enantioselectives olute-solventi nteractions in those mesophases,e nantiomers orient themselves differently,w hich leads to different NMR observables such as, for instance, 13 Cc hemical shifts because of different 13 Cc hemical shift anisotropy terms.…”

“…Cyclobis[5]helicene 3 b was prepared in the racemic series as previously described by using a glyoxylic Perkin reaction for the formation of the intermediate flexible macrocycle 4 , which was rigidified by a four‐fold Mallory photocyclization (Scheme ). Racemic [5]helicene 6 was prepared by the same approach …”

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

“…To obtain a pentagonal dibenzo[ a,j ]coronene‐diimide, we conceived a synthetic approach that relies on our recent finding that the cyclization of [5]helicene fragments to benzo[ ghi ]perylene moieties can be achieved with aluminum chloride in DCM even in the presence of carboxylic ester substituents, which prove to be surprisingly inert towards attack by the Lewis acid under these conditions …”

“…The N‐alkyl or ‐aryl substituents allow tuning of the solubility, crystal packing and self‐assembly without modifications on the arene core. Perylene diimides (PDIs) with branched alkyl substituents such as 1 (Scheme ) are known to self‐assemble into columnar mesophases, which are of interest for their propensity to exhibit anisotropic charge transport, and we have in the past developed a variety of di‐ and triimide derivatives of larger polycyclic arenes that form columnar mesophases over larger temperature ranges than PDIs and vary in bandgap and LUMO energy levels …”