TNF Induced Switching of Columnar Rectangular to Hexagonal Assemblies in a New Class of Triphenylene-Based Room Temperature Discotic Liquid Crystals

A straightforward synthesis of triphenylenebased oligomeric systems that self-organize into room temperature columnar structures is presented. The compounds with longer spacer length (m = 10 and 12) exhibit columnar rectangular (Col(r)) mesophase whereas the compound with m = 8 exists in glassy Col, state. Interestingly, the Col, self assembly of these compounds switches to columnar hexagonal (Col(h)) on doping the compounds with 2,4,7-trinitrofluorenone (TNF). For the dopant concentration of 1:1 with respect to native compound, an intermediate transition state between Col, and Colh phase was observed which completely transformed into the hexagonal phase on increasing the concentration to 1:2 (compound: TNF) and afterward. Both the Col, and Colh self assemblies have been well resolved by detailed X-ray analysis. These kind of oligomeric compounds generally possess a combination of desirable alignment properties analogous to monomeric compounds and long-lived glassy states similar to that of polymeric mesogens. In addition, charge hopping behavior is expected to increase in these compounds due to donor acceptor interactions. Overall, these compounds can find possible potential applications in semiconductor devices.