Two-photon absorption (TPA) properties of 1,3,5-tricyano-2,4,6-tris(styryl)benzene derivatives havebeen investigated. Comparison of the absorption and fluorescence spectra reveals that these compounds showlarge Stokes shifts, which increase gradually as the conjugation length increases. One-photon absorption andexcitation spectra are similar except that the latter exhibit several peaks near
max. It is also found that the one-and two-photon-induced fluorescence excitation spectra are quite similar, which indicates that the one- andtwo-photon allowed-excited states are the same. The peak TPA cross section values (
max) measured withnanosecond pulses by the two-photon-induced fluorescence method are in the range (50-2620) × 10
-50 cm
4s/photon. The
max value increases as the donor strength and conjugation length increase. A linear relationshipis observed between
max and
![](/images/gifchars/beta2.gif)
, and this
![](/images/gifchars/delta.gif)
-
![](/images/gifchars/beta2.gif)
relationship is found to serve as a useful synthetic strategy forthe design of novel TPA dyes with the octupolar structure.