Discotic liquid crystals (LCs) are popular organic materials having properties including long range self-assembly and ease of processability that make them suitable candidates for various optoelectronic applications. The molecules in discotic liquid crystals often assemble in columns providing one dimensional semiconductor charge transport. Amongst the many varieties of discotic systems, the most widely studied have a triphenylene core. We have been studying the impact of terminal tail functionalization of calamitic liquid crystals and have now begun to examine this design feature in discotics as well. Here we have proposed and synthesized a series of hexapentyloxytriphenylene (HAT-5) derivatives with a varying extent and symmetry of terminal tail fluorination. The various fluorine terminated HAT-5 were successfully prepared using FeCl3 mediated oxidative dimerization and trimerization approaches and their physical properties were studied. Generally, tail fluorination was found to destabilize the discotic phase. However, an interesting result of reinstating LC phase was found when a polar nitro group was installed in the core of HAT-5 bearing six fluorine terminated tails. This nitro derivative was mesogenic far below room temperature suggesting its potential application in devices that operates at room temperature and/or below room temperature.

Synthesis and properties of fluorine tail terminated hexapentyloxy triphenylene (HAT-5) discotic liquid crystals

ACS Spring Meeting 2021

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