Novel benzylidene cyclopentanone dyes for two-photon photopolymerization

Two novel benzylidene cyclopentanone dyes (1 and 2) containing coumarin moiety were synthesized. Their photophysical properties were investigated using UV–vis spectra, fluorescence spectra and two-photon excited spectra. The maximum two-photon absorption cross-sections (δmax) of two compounds were determined as 939 GM and 1150 GM, respectively, with femtosecond laser pulses. Combined with commercial photoinitiator 4,4′-dimethyl-diphenyliodinium hexafluorophosphate (Omnicat 820), both of two dyes exhibited higher sensitizing photopolymerization efficiency than the common used high-efficient photosensitizer 2,5-bis-[4-(dimethylamino)-benzylidene]-cyclopentanone in one-photon photopolymerization experiments. Using 2 as sensitizer or initiator directly, 2D and 3D nanopatterns were successfully fabricated by two-photon initiated polymerization.