Photoreaction and photopolymerization studies on fluoflavin dye–pyridinium salt systems

Several dyes derived from 5,12-dihydroquinoxalino[2,3b]quinoxaline have been synthesised and evaluated as sensitizers for alkoxypyridinium salt photodecomposition. The results are discussed on the basis of the free energy change for electron transfer from fluoflavin dyes to alkoxypyridinium compounds. The mechanism of dye photobleaching is supported by DFT calculations, spectroscopic characterization of the cation radical of the dye, and the quantum yields of sensitised proton formation. Fluoflavin dyes are shown to be useful as photoinitiators for sensitizing compounds to photooxidation. Photoredox pairs consisting of fluoflavin dyes and alkoxypyridinium salt are found to be effective initiation systems for free radical polymerization of methyl acrylate and trimethylolpropane triacrylate (TMPTA) using VIS light.