Structural Effects in the Indanedione Skeleton for the Design of Low Intensity 300-500 nm Light Sensitive Initiators

Newly synthesized indanedione derivatives combined with an iodonium salt, N-vinylcarbazole, amine, phenacyl bromide, or 2,4,6-tris(trichloromethyl)-1,3,5-triazine have been used as photoinitiating systems upon very low visible light intensities: blue lights (e.g., household blue LED bulb at 462 nm) or even a halogen lamp exposure. One of them (ID2) is particularly efficient for cationic, radical and thiolene photopolymerizations as well as for the synthesis of interpenetrated polymer networks (IPNs). It can be useful to overcome the oxygen inhibition. ID2 based photoinitiating systems can also be selected for the reduction of Ag+ and the in situ formation of Ag(0) nanoparticles in the synthesized polymers. The (photo)chemical mechanisms are studied by electron spin resonance spin trapping, fluorescence, cyclic voltammetry, laser flash photolysis, and steady state photolysis techniques.