Highly fluorescent naphthalimide derivatives for two-photon absorption materials

Novel multi-branched naphthalimide derivatives (TPA-NA1, TPA-NA2, and TPA-NA3) were synthesized by the Sonogashira reaction of N-butyl-4-bromo-1,8-naphthalimide with mono-, di-, and tri-ethynylated triphenylamine. The fluorescence increases with the increase of branch number and the quantum yield is as high as 0.87 for TPA-NA3 in toluene. Two-photon absorption cross sections of TPA-NA3, TPA-NA2, and TPA-NA3 were determined to be 0.42 x 10(-20) cm(4)/ GW, 1.4 x 10-20 cm(4)/GW and 1.0 x 10(-20) cm(4) /GW (open aperture Z-scan, 120 fs, 780 nm), respectively.