Multibranched benzylidene cyclopentanone dyes with large two-photon absorption cross-sections

Multibranched benzylidene cyclopentanone dyes with a triphenylamine core were synthesized. Their two-photon optical properties were characterized using a Ti: sapphire femtosecond laser. The results showed that the two-photon absorption cross- sections (delta) of these compounds were increased with increasing numbers of branches. The largest d value of the three-branched compound 3 was 3298 GM which was almost six times larger than that of a model compound, 2,5-bis-[4-(dimethylamino) benzylidene] cyclopentanone ( BDMA). The sensitizing efficiencies of three new dyes in photopolymerization systems were all higher than that of BDMA matching with the commercial initiator 4,4'-dimethyldiphenyliodinium hexafluorophosphate (Omnicat 820). The two-photon polymerization initiated by the bimolecular system composed of compound 3 and Omnicat 820 was investigated under femtosecond laser pulses.