Helical packing of discotic hexaphenyl hexa-peri-hexabenzocoronenes: Theory and experiment

Wojciech Pisuia, Željko Tomović, Mark D. Watson, Klaus Müllen, Jörg Kussmann, Christian Ochsenfeld, Thorsten Metzroth, Jürgen Gauss

Research output: Contribution to journalArticlepeer-review

70 Scopus citations

Abstract

The arrangement of discotic hexa-peri-hexabenzocoronenes (HBCs) into columnar helical superstructures has been investigated in relation to their molecular architecture. The supramolecular structure of two hexaphenyl- substituted HBC derivatives, differing only in the chiral/achiral nature of the attached alkyl side chains, was studied by circular dichroism and temperature-dependent wide-angle X-ray diffraction on oriented filaments. A structural model in agreement with the experimental observations was developed on the basis of accompanying quantum-chemical calculations. The helical organization along the self-assembled columnar structures was induced by the steric requirements of the bulky phenyl rings near the aromatic core, i.e., by their rotation out-of-plane with respect to the aromatic core. On the other hand, a uniform handedness of the twist was generated by chiral alkyl substituents. At higher temperatures the degree of helical organization decreases due to lateral and longitudinal dynamics of the discotic molecules. Annealing at ambient conditions improved the long-range arrangement of the discs along the columnar structures. This reorganization indicated a self-healing of the plastic material which is desirable for application of discotics as active layers in electronic devices. The helical packing resulted in a considerable stability of the mesophase up to 500°C, which has not been reported for a discotic so far.

Original languageEnglish
Pages (from-to)7481-7487
Number of pages7
JournalJournal of Physical Chemistry B
Volume111
Issue number26
DOIs
StatePublished - Jul 5 2007

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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