Purpurin derivatives as visible-light photosensitizers for 3D printing and valuable biological applications

We report the synthesis of new visible-light photosensitizers derived from purpurin (mono-allyl- and triallyl-purpurin), and their use as type II photoinitiating systems when associated with N-methyldiethanolamine, bis(4-methylphenyl) iodonium hexafluorophosphate or tri-functionalized thiol (trimethylolpropane tris(3-mercaptopropionate)) for cationic and free-radical photopolymerization, and the initiation of thiol-ene reactions. These photoinitiating systems showed good initiating properties in laminate or under air upon visible-light exposure, i.e. LED@405 nm, 455 nm, 470 nm, 530 nm, and a Xe lamp. Steady-state photolysis, electron paramagnetic resonance, fluorescence analysis and laser flash photolysis have clearly highlighted the photochemical properties of the different photoinitiating systems and proved that purpurin derivatives could act as electron donors or as proton/proton-coupled electron transfer promoters when associated with appropriate additives. For the first time, we also demonstrated the capability of triallyl purpurin to produce newly designed 3D objects by 3D photoprinting technology. Interestingly, the photosensitizers from new 3D materials incorporating triallyl-purpurin have undoubtedly shown tremendous antibacterial properties with more than 99% of inhibition of bacterial adhesion upon visible-light exposure, even after many antibacterial cycling experiments, thus showing their capability to be recycled.

Automated summary

The study presents the synthesis and application of new visible-light photosensitizers derived from purpurin in type II photoinitiating systems for various photopolymerization reactions and thiol-ene reactions. It demonstrates the photochemical properties of these systems, showing that purpurin derivatives can act as electron donors or proton/proton-coupled electron transfer promoters with appropriate additives. Triallyl purpurin is shown for the first time to produce 3D objects using 3D photoprinting technology, and photosensitizers incorporating triallyl-purpurin exhibit significant antibacterial properties under visible-light exposure, even after multiple antibacterial cycling experiments, indicating their potential for recyclability.