Nonlinear Optical and Two-Photon Absorption Properties of 1,3,5-Tricyano-2,4,6-tris(styryl)benzene-Containing Octupolar Oligomers

Octupolar oligomers containing 2-12 molecules of 1,3,5-tricyano-2,4,6-tris(styryl)benzene derivatives have been synthesized and their nonlinear optical and two-photon absorption (TPA) properties were determined. The beta(0) values are in the range of (85-1219) x 10(-30) esu and increase monotonically with the increasing number of the octupolar units within the molecule. The two-photon-induced fluorescence excitation spectra are quite similar to the single-photon absorption spectra except that the wavelength is doubled, indicating that the one- and two-photon allowed excited states are the same. The peak TPA cross-section values (delta(max)) measured with nanosecond pulses by the two-photon-induced fluorescence method are in the range (3010-62, 930) x 10(-50) cm(4)s photon(-1). The delta(max) increases as the number of the octupolar units in the molecules increases. A linear relationship is observed between delta(max) and beta, and this delta-beta relationship serves as a useful design strategy for the synthesis of novel octupolar oligomers and polymers with large TPA and beta.