Extended-core discotic liquid crystals based on the intramolecular H-bonding in N-acylated 2,2'-bipyridine-3,3'-diamine moieties

A new type of disc-shaped molecule (la-c) has been synthesised and characterised. The molecules were built up by linking three lipophilic, N-monoacylated 2,2'-bipyridine-3,3'-diamine wedges to a central 1,3,5-benzenetricarbonyl unit. They show liquid crystalline behaviour, as shown by DSC, polarisation microscopy and X-ray diffraction. In all cases the mesophase was characterised as a D-ho phase. From H-1 NMR results it was shown that the interior of compounds 1 a-c preferentially adopts a C-3 symmetrical conformation owing to strong intramolecular H-bonding, which gives rise to an extended core. This large core induces strong interactions between molecules, leading to mesophases of enhanced thermal stability.