Iptycenes and Their Derivatives in Material Science

Abstract

In general, all compounds with liquid crystalline properties would be consisted of a rigid core and long flexible chains, which blocked the formation of completely ordered system. Thus, the systems containing the rigid iptycene core and the flexible long alkyl or alkoxy chains seemed to be potential candidates as liquid crystalline materials (Chem Soc Rev 38:3301–3316, 2009). In the early 1990s, Simon and Norvez (J Chem Soc Chem Commun 1990:3407–3412, 1990; J Org Chem 58:2414–2418, 1993) synthesized triptycene derivative 1 containing five long paraffinic chains (Fig. 8.1) and found that it showed the mesomorphic behavior at room temperature. The rigid triptycene core of this pentasubstituted derivative (1) regularly arrayed in a hexagonal lamellar structure, along with the long chains extending above and below the layer, which was indicated by its X-ray diffraction patterns. The triptycene derivative 1 exhibited the mesomorphic property at room temperature, probably because the cell areas were big enough to hold the chains at disordered state. On the other hand, it was found that the triptycene derivative 2 (Fig. 8.1) with six alkoxy chains and an aromatic core would form the symmetric compatible lamellar lattices. However, the cell areas in these lamellar lattices were too small to be available for all chains in a disordered state, which led to the crystalline state instead of the mesomorphic state.