title: Plank-shaped column-forming mesogens with substituents on one side only.
abstract: Prolonged glyoxylation of pyrenyl-1-glyoxylic acid ethyl ester leads to a mixture of isomers with polar pyrenylene-1,8-diglyoxylic acid as the main product, whereas the centrosymmetric 1,6-isomer is obtained in good yield from the corresponding dibromopyrene. Perkin condensations followed by Pd-catalyzed cyclizations lead to isomeric dinaphthopyrene-tetracarboxdiimides that self-assemble into columnar liquid crystals of hexagonal and rectangular symmetry, of which the rectangular mesophases have unusually elongated unit cells. The cisoid diimides with both alkylimide substituents on the same side of the oblong arene system show a much greater tendency to self-assemble into fluid stacks of disks than their centrosymmetric isomers. With racemically branched alkyl substituents, uniform vertical surface alignment of the columns in the high-temperature hexagonal mesophase is resilient to cycling through the lower-temperature rectangular and crystalline phases.
authors.affiliation: Centre National de la Recherche Scientifique, Centre de Recherche Paul Pascal, 115 avenue Schweitzer, 33600 Pessac (France).
authors.forename: Edivandro
authors.initials: E
authors.lastname: Girotto
authors.forename: Marli
authors.initials: M
authors.lastname: Ferreira
authors.forename: Parantap
authors.initials: P
authors.lastname: Sarkar
authors.forename: Ahmed
authors.initials: A
authors.lastname: Bentaleb
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Hillard
authors.forename: Hugo
authors.initials: H
authors.lastname: Gallardo
authors.forename: Fabien
authors.initials: F
authors.lastname: Durola
authors.forename: Harald
authors.initials: H
authors.lastname: Bock
keywords: donor-acceptor systems; fused-ring systems; liquid crystals; phase transitions; self-assembly; stacking interactions