Three series of multi-branched s-triazine derivatives with one, two or three branches have been synthesized. For each series, the linear absorption (peak position: 390～440 nm) and emission spectra (peak position: 460～580 nm), along with the two-photon exited fluorescence spectra excited at 800 nm, showed regular red-shifts as the branch number was increased, and their spectral intensities were significantly enlarged from one- to three-branched structures. In addition, the difference of dipole moment (Δμ_eg) between the ground and the excited states became larger as the branch number was increased from 1 to 3. The two-photon absorption cross section σ was non-linearly increased with the increase of the branch number and the reduced σ, indicating a remarkable cooperative enhancement of σ in the multi-branched s-triazine derivatives.

Key words: s-triazine, multi-branched, synthesis, two-photon absorption, cooperative enhancement