Coumarin derivatives with enhanced two-photon absorption cross-sections

A series of ketocoumarin derivatives were synthesized using Aldol condensation and Wittig reactions and their one- and two-photon photophysical properties were investigated. Two-photon absorption cross-sections (δ) of the derivatives revealed that most of the new compounds possessed δ values that were some one to two orders of magnitudes larger than those of commercial coumarin dyes. The largest δ value within measured range was obtained as 1570 GM, which is comparable to that of reported strong two-photon absorption compounds. These novel derivatives containing the functional ketocoumarin group should open new opportunities for two-photon polymerization.