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Phenylethynyl siJbstituted benzenes 1, 2 and 3 are synthesized by the Pd-coupling reaction of phenylacetylene with the corresponding bromobenzene; the third-order optical non-linearity [X(3)(03)1 increases with the participation of n-conjugation through the triple bond as determined by the degenerate four-wave mixing (DFWM) method in a c h I o rof o rm sol u:i on.

We report two-photon absorption properties of newly synthesized compounds consisting of styrylpyridines or their triflates linked by a diacetylene p-bridge in a symmetric way as well as the compounds containing the same substituent groups linked by a phenylenevinylene-type p-bridge. Femtosecond open aperture Z-scan measurements revealed that the two-photon absorption cross-sections s (2) of the diacetylene compounds in DMSO were in the order of 10 248 cm 4 s molecule 21 photon 21 in the wavelength range of 650-800 nm. The largest value was found to be 8.50 6 10 248 cm 4 s molecule 21 photon 21 at 764 nm for the methoxy-substituted triflate of the diacetylene compound. This value is one of the largest values obtained for molecules of a similar size by use of femtosecond pulses, indicating that the incorporation of the diacetylene moiety as the p-bridge would be useful for two-photon dyes.