The influence of alkyl chain substitution pattern on the two- and three-dimensional self-assembly of truxenone discogens

Abstract

The synthesis of new discotic liquid crystals and the study of self-assembly behaviours are important for the supramolecular chemistry and organic electronics. Six new truxenone discogens 7a–f with different alkyl chain substitution patterns were synthesised and all exhibited only one three-dimensional ordered hexagonal columnar mesophase with wide temperature ranges including room temperature, which were characterised with polarising optical microscopy, differential scanning calorimetry and X-ray diffraction. The self-assembly behaviours in solutions were studied by using concentration-variation ¹H NMR and scanning electron microscopy. The two-dimensional ordered self-assembly of 7c and 7f on the liquid–solid interface of highly oriented pyrolytical graphite were imaged by scanning tunnelling microscopy, and the results showed that the two-dimensional monolayer self-assembled structures on the atomically flat surfaces can be controlled by the peripheral alkyl chain substitution patterns.

Keywords:

• truxenone
• liquid crystal
• self-assembly
• nanostructure
• scanning tunnelling microscopy
• scanning electron microscopy

Funding

The research was supported by the National Natural Science Foundation of China (NSFC) [grant number 51273133], [grant number 51073112], [grant number 50973076].

Supplemental data

The experimental; synthesis and characterisations of the intermediates and target compounds; ¹H NMR and ¹³C NMR spectra; The HOMO and LUMO of the hexakis(methoxy)truxenone. Supplemental data for this article can be accessed here.