New Discotic Mesogens Based on Triphenylene-Fused Triazatruxenes: Synthesis, Physical Properties, and Self-Assembly

Abstract

A new type of discotic mesogen based on triphenylene-fused triazatruxenes was prepared by microwave-assisted 6-fold Suzuki coupling reactions from hexabromotriazatruxene, followed by FeCl3-mediated oxidative cyclodehydrogenation. These disklike molecules showed extended π-conjugation, compared with the triphenylene and triazatruxene themselves. More importantly, they possess desirable HOMO energy levels, which allow efficient charge injection from electrodes such as gold electrodes. Their thermal behavior and self-assembly were studied by different techniques such as thermogravimetric analysis, differential scanning calorimetry, polarizing optical microscopy, and variable-temperature X-ray diffraction. These new discotic mesogens have very good thermal stability and show thermotropic liquid crystalline behavior. Ordered columnar liquid crystalline phase and crystalline phase were observed in both compounds with tunable phase transition temperatures and mesophase widths. The charge carrier mobilities of th...