Porphyrin derivatives: promising perspectives in visible/IR light photopolymerization

Photopolymerization using visible light represents a significant progress in the synthesis of materials, providing a more economical and ecological method. Therefore, the necessity to develop new and more effective photoinitiating systems is essential, and the use of porphyrin derivatives may become a great alternative in the coming years. According to their high absorbance, their ability to form reactive species under light irradiation, porphyrin derivatives are particularly attractive candidates for the photopolymerization process. The convenience of their functionalization, allowing optimization of their photophysical and photochemical properties, makes them particularly interesting for developing new photoinitiators/ photosensitizers that are effective under visible or IR light irradiation. This review explores the main aspects that need to be anticipated to obtain optimized photoinitiating systems based on porphyrin derivatives. The different routes for synthesizing and functionalizing porphyrins are described, and both the photophysical and photochemical properties of the modified porphyrin derivatives including the absorbance properties, the reactivity of the excited states and the redox capacities of these molecules, are highlighted. Finally, particular attention are attached to promote the use of porphyrin derivatives as photoinitiating systems for free-radical, cationic and photocontrolled radical polymerization.