tar-shaped oligo(p-phenylene)-functionalized truxenes as blue-light-emitting materials: synthesis and the structure–property relationship

In this contribution, we described a strategy to prepare a series of well-defined, blue-light-emitting materials with truxene unit as the core and oligo(p-phenylene) (from one to four phenyl units) as the branches. The Suzuki coupling reactions between truxene bromide derivatives and phenylboronic acid or 1,1′-biphenyl-4-boronic acid catalyzed by Pd(0) afforded the desired compounds Tr-1-Ph, Tr-2-Ph, Tr-3-Ph and Tr-4-Ph. With stepwise increases of the benzene rings, the desired molecules exhibited exceptional photophysical properties as well as increasing thermal stability. Tgs increased from 39 °C for Tr-1-Ph to 192 °C for Tr-4-Ph. The absorption and the emission maximum peaks of these four compounds were red-shifted from the ultraviolet to the blue region with the increase of effective conjugation length. All results demonstrated that the physical properties were facilely tuned by connecting different types and different conjugated lengths to C-2, C-7, and C-12 positions of the truxene core.