Tristriazolotriazines: Luminescent Discotic Liquid Crystals

摘要

Tristriazolotriazines (TTT) are new tetracyclic and planar cores for discotic liquid crystals. Two symmetrical isomers are known, paddle-wheel type t-TTTs and r-TTTs with the shape of a propeller. Cyclocondensation of chlorotriazoles gives r-TTTs, Huisgen reaction of tetrazoles and cyanuric chloride yields t- TTTs with tangentially attached substituents. Many alkoxyphenyl- substituted t-TTTs form broad mesophases, typically with a hexagonal columnar structure. These luminescent molecules, when heated above 200 °C, suffer a thermal isomerization. A threefold ring opening/ring closing mechanism transforms t-TTTs via unsymmetrical isomers to r-TTTs. Thermotropic properties are largely influenced by planarization and increase of molecular diameter. Increased melting points, even the complete loss of liquid crystallinity have been observed, but also the gain of mesomorphism.