A series of multi-branched pyrazine derivatives with two, three and four branches have been synthesized. The linear absorption (peak position: 290～390 nm) and emission spectra (peak position: 400～510 nm) along with the two-photon excited fluorescence (TPEF) spectra (excited at 720 nm) showed regular red-shifts as the branch number increased, and the fluorescence quantum yields of the pyrazine derivatives increased (from 0.13 to 0.25). In addition, the two-photon absorption (TPA) cross section σ non-linearly increased with a ratio of 1∶2.8∶3.7, which is near to the ratio of the square of branching number n2 (1∶2.25∶4), indicating a remarkable cooperative enhancement of σ in the multi-branched pyrazine derivatives. The σ value of the four-branched compound is 1007 GM. It was also found that the ortho-/para-branching pattern took great advantage over the meta-branching pattern in the linear fluorescence and TPEF.

Key words: multi-branched structure, two-photon absorption, pyrazine, synthesis