Room temperature liquid crystalline perylene diester benzimidazoles with extended absorption

Titelangaben

Wicklein, André ; Muth, Mathis-Andreas ; Thelakkat, Mukundan:
Room temperature liquid crystalline perylene diester benzimidazoles with extended absorption.
In: Journal of Materials Chemistry. Bd. 20 (2010) Heft 39 . - S. 8646-8652.
ISSN 1364-5501
DOI: https://doi.org/10.1039/C0JM01626H

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Abstract

The synthesis, characterization and thermotropic properties of novel asymmetrically substituted
discotic molecules, perylene diester benzimidazoles (PDBIs), are presented. PDBIs were designed with
an imidazole unit at 3,4 positions and a bisester moiety at 9,10 positions of the perylene tetracarboxylic
acid core. By attaching linear or branched aliphatic substituents at the ester moiety and two alkyl or
alkoxy substituents at the benzimidazole unit, sufficient solubility and the flexibility to obtain
mesophases was guaranteed. Thermotropic behaviour, which is strongly influenced by the nature of the
respective substituents at the diester and benzimidazole moiety, was investigated using differential
scanning calorimetry (DSC), polarization optical microscopy (POM) and X-ray diffraction
measurements (XRD). All PDBIs under investigation self-organize into liquid crystalline columnar
hexagonal phases (Colh), among them PDBI-3 even at room temperature. Also the formation of a room
temperature columnar plastic phase (Colhp) and the formation of a lamellar phase was observed. Due to
extension of the p-conjugation system, the absorption of these well soluble discogens is significantly
extended to longer wavelengths in the visible regime up to 680 nm.