Centripetal triazine chromophores: towards efficient two-photon absorbers and highly emissive polyimide films

Four centripetal (D-pi-)(3)-A chromophores based on s-triazine central acceptors and three amino donor-terminated branches were prepared. These chromophores were proved to be thermally stable up to 300 degrees C with a tuneable HOMO-LUMO gap (3.02-2.51 eV) and longest-wavelength absorption/emission maxima within the range of 390-427/485-551 nm. Relatively large Stokes shift up to 8000 cm(-1), quantum yields up to 78% and fluorescence lifetimes ranging between 2 and 4 ns were observed based on the chromophore structure and the used environment. In general, varying the pi-linker is proved to be a very useful strategy to tune the fundamental properties of these chromophores. Two-photon absorption measurements showed good to excellent cross-sections reaching 1000 GM. High-quality and well-transparent polyimide films doped with chromophores (0.1%) were further prepared, and showed bright emission in blue and yellow/green regions.