Columnar Liquid‐Crystalline Dinaphthoperylenetetracarboxdiimides

Abstract

Although the double Friedel-Crafts acylation of arenes with ethyl chloroglyoxylate is hindered by the strongly deactivating effect of the first-entering glyoxylic substituent, the double reaction is successful with the reactive arene perylene under long reaction times and with concomitant ester hydrolysis. The reaction is regiospecific, giving the 3,9-regioisomer exclusively. This perylenylenediglyoxylic acid is condensed first with o-bromophenylacetic acid and then with α-branched alkylamines to yield the title compounds. Whilst the corresponding tetraalkyl esters only show monotropic mesophases, these diimides show enantiotropic columnar mesophases that can be maintained at room temperature if racemically branched alkyl chains of moderate size are used. A palladium-induced C-C bond migration during the build-up of the arene system leads to an isomeric side product of reduced symmetry that can be isolated by aggregation-controlled chromatographic separation. The HOMO and LUMO energies of the title compounds are considerably higher than those of established perylenetetracarboxdiimides.

Stabilization of the Columnar Mesophase of Perylenediimide by Racemic Triple Tails

“…Recently we have found that dissymmetrizing the swallow‐tail alkyl residues greatly improves the columnar mesogenic behavior of various polycyclic aromatic di‐ and tri‐imides, racemic 1‐hexyldecyl being particularly efficient in inducing large mesophase temperature ranges . As dissymmetric 1‐hexyldecyl differs only very moderately from symmetric 1‐heptyloctyl (as in 1 ) in combined alkyl chain lengths, we hoped that it would also induce a mesophase over large temperatures in PDI 3 .…”

Plank‐Shaped Column‐Forming Mesogens with Substituents on One Side Only

“…Mesogenic materials with two such imide moieties are rare because two substituents are often not enough to induce liquid crystalline behavior, but the use of α‐branched (“swallow‐tailed”) alkylimide substituents RR′CHN(CO‐) 2 yields in some cases columnar mesophases, especially if the two branches R and R′ are not identical, yielding stereoisomeric mixtures with increased stabilization of the mesophase against crystallization 4. 5…”

“…Having recently found that swallow‐tailed dinaphtho[1,2‐b; 1,2‐k]perylene‐tetracarboxdiimides 1 , derived from centrosymmetric perylenylene‐3,9‐diglyoxylic acid 2 through a double Perkin condensation with 2‐bromophenylacetic acid 3 (Figure 1), form enantiotropic columnar mesophases,5 we aimed at preparing analogous dinaphtho[2,1‐a;2,1h]pyrene‐diimides 4 by a two‐fold Friedel–Crafts alkylation of pyrene with ethyl chloroglyoxylate ClCOCO 2 Et.…”

“… Synthesis of columnar liquid crystalline dinaphthoperylene‐dicarboximides 1 from perylenylene‐diglyoxylic acid 2 with bromophenylacetic acid 3 by Perkin condensation followed by Pd‐catalyzed dehydrobromination and final imidification with RR′CHNH 2 5…”

Columnar Liquid‐Crystalline Dibenzopentacenodithiophenes by Photocyclization

“… Synthesis of dibenzopentacenodithiophene‐tetraester 9 and related dinaphthoperylene‐tetraester 3 , and structure of the derived diimides 7 and 4 together with complementary acceptor‐type perylene‐diimide 5 …”