Recent advances on carbazole-based photoinitiators of polymerization

Photoinitiators of polymerization that can be activated under visible light and low intensity are actively researched as these compounds constitute the next generation of photoinitiators that will replace the controverted UV-photoinitiators. Over the years, a family of compounds has been identified as being highly promising in light of its remarkable photoinitiating ability, photochemical stability, low cost and easiness to functionalize, namely carbazoles. In this review, an overview of the different carbazole-based photoinitiators reported to date is presented. Interestingly, carbazoles have mostly been used as electron donors in push-pull structures, as photosensitizers for iodonium salts, as ligands for ferrocenium salts or as chromophores for phenacyl onium salts. These different applications clearly demonstrate the versatility of this structure used as the elemental building block for the design of UV, near-UV or visible light photoinitiators.