In this paper we present the synthesis and characterization of three different thermotropic liquid crystalline derivatives of hexabenzocoronene (HBC), substituted at the periphery by six chiral or racemic branched (3,7-dimethyloctanyl) chains, namely the chiral 5a, racemic 5b, and mono-bromo functionalized 18 carrying five alkyl chains. Improved methods for synthesis of HBC precursors, largely relying on transition-metal catalyzed coupling reactions, are also described. Solubility and processability are increased while the thermal K→DH transitions are shifted to lower temperatures, relative to analogous HBCs carrying n-alkyl chains. In case of substitution with a chiral branched alkyl chain, 5a, strong signals have been recorded by means of circular dichroism spectroscopy. All new compounds were characterized by 1H, 13C NMR, and UV-Vis spectroscopy, and FD-MS. Preliminary mesophase characterization is carried out by differential scanning calorimetry (DSC) and polarized light microscopy. In the course of the DSC experiments, optically pure and racemic HBC derivatives were compared.
|Number of pages||15|
|State||Published - Apr 23 2001|
Bibliographical noteFunding Information:
This research was supported by the TMR European Research Program through the SISITOMAS project and the Volkswagen-Stiftung. We thank Petra Räder for conducting ‘last-minute’ DSC and TGA experiments. The help and advice from Professor Dr E. W. Meijer and his group, especially from Luc Brunsveld, during the CD experiments is gratefully acknowledged.
- Chiral mesophase
- Discotic liquid crystals
- Polyaromatic hydrocarbons (PAH)
ASJC Scopus subject areas
- Drug Discovery
- Organic Chemistry