Amino and nitro substituted 2-amino-1H-benzo-[de]isoquinoline-1,3(2H)-diones: as versatile photoinitiators of polymerization from violet-blue LED absorption to a panchromatic behavior

Four different 2-amino-1H-benzo[de]isoquinoline-1,3(2H)-dione derivatives (NDNs) bearing nitro-or amino-substituents have been prepared and incorporated into photoinitiating systems together with an iodonium salt, N-vinylcarbazole, an amine or 2,4,6-tris(trichloromethyl)-1,3,5-triazine. The ring-opening cationic polymerization of epoxides as well as the free radical polymerization of acrylates upon exposure to various visible LEDs (e.g. LEDs at 405 nm, 455 nm or 470 nm) could be performed. Reactions under green or red light (e.g. laser diodes at 532 or 635 nm) are also feasible. Compared to the well-known camphorquinone-based systems, some of the novel NDN-based combinations employed here exhibit a much higher polymerization efficiency. A panchromatic behavior can also be observed with a specifically designed compound bearing two nitro groups (e.g. radical polymerization or thiol-ene processes can be promoted upon blue, green or red light). This outstanding performance paves the way to polymerization under soft conditions. Their photochemical properties and structure/efficiency relationships have been investigated using steady state photolysis, fluorescence, cyclic voltammetry, laser flash photolysis, and electron spin resonance spin trapping techniques.