Synthesis and properties of tribranched chromophores with triazine and fluorene units

Two tribranched chromophores, 1,3,5-triazine as electron deficient core, 9,9-dimethylfluorene as π-conjugated bridge, diphenylamino (4a) and naphthylamino (4b) as electron-donating end-groups, were successfully prepared via Buchwald–Hartwig coupling reaction. Their linear photophysical and two-photon absorption (TPA) properties were investigated by absorption, fluorescence and nonlinear transmission method, respectively. The absorption cut-offs of the chromophores are below 550 nm and both chromophores have strong fluorescence emission. The compound 4a (206.3 GM) exhibits larger TPA cross-section than 4b (57.8 GM) in the femtosecond regime at 800 nm.