Synthesis and two-photon absorption properties of novel heterocycle-based organic molecules

Four novel heterocycle-based two-photon absorption chromophores were designed and synthesized. In these molecules, heterocyclic benzothiazole and oxadiazole derivatives are used as acceptors (A), and formyl group is another acceptor (A') applied. These dyes have the structural motif of A-pi-D-pi-A or A-pi-D-pi-A'. All the chromophores show wide linear optical transparency and strong single-photon and two-photon excited emission. The two-photon absorption cross-sections of molecules with A-pi-D-pi-A backbone with two heterocycle-based acceptors are as large as 521 GM and 461 GM at the wavelength of 788 nm in the femtosecond regime. The molecules of A-pi-D-pi-A' framework show relatively low two-photon absorbing activities due to the small pi-conjugation systems.