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 cha racterised. The molecules were built up by linking three lipophilic, N -monoacylated 2,2'-bipyridine-3,3'-diamine wedges to a central 1,3,5-b enzenetricarbonyl unit. They show liquid crystalline behaviour, as sho wn 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 adop ts a C-3 symmetrical conformation owing to strong intramolecular H-bon ding, which gives rise to an extended core. This large core induces st rong interactions between molecules, leading to mesophases of enhanced thermal stability.