Synthesis and Characterization of Novel Mesomorphic Chromenonapthophenathridines

Abstract

Heterocyclic discotic liquid crystals containing heteroatoms such as O, N, S, Se, P as part of pi-conjugated framework has revolutionized organic semiconductors research. The presence of heteroatom in pi-conjugated core has been reported to strikingly influence the self-assembling properties. In this work we have synthesized novel chromenophenanthridines where the incorporation of oxygen facilitates the in plane ordering of central core and improves liquid crystalline character in these molecules. This paper elucidates the mesomorphic behavior of chromenonapthophenanthridines prepared via tandem Pictet Spengler cyclisation and ipso-aromatic substitution in one pot. The synthesized compounds exhibited wide range enantiotropic columnar hexagonal phase. The mesomorphic behavior was suggested as a function of peripheral alkyl chains. The shorter homologue was found to exhibit hexagonal columnar plastic phase whereas higher ones exhibit hexagonal columnar phase.