Synthesis of novel oxidizable polymerization sensitizers based on the dithiinoquinoxaline skeleton

Novel dyes, based on the dithiinoquinoxaline skeleton, were synthesized and characterized using 1H NMR spectroscopy and chemical ionization mass spectroscopy. Their spectral properties, such as absorption, emission spectra and quantum yield of fluorescence, were also measured. Electron donating properties of the title compounds were estimated on the basis of DFT calculations. The studied dyes were used as oxidizable sensitizers for 2,4,6-tris(trichloromethyl)-1,3,5-triazine (Tz). The dye/Tz photoredox pairs were found to be effective visible-wavelength initiators of free radical polymerization. The ability of these systems to act as photoinitiators strongly depended upon the free energy change of the photoinduced electron transfer from the excited dyes to Tz. It has been shown that the intermolecular electron transfer is the limiting step in the photopolymerization initiated by these studied initiator systems.

► Novel dyes, based on the dithiinoquinoxaline skeleton, were synthesized.
► Their electron donating properties were estimated on the basis of DFT calculations.
► Two component initiator system for visible-light initiated radical polymerization.
► Dyes as the sensitizers and tris(trichloromethyl)-1,3,5-triazine as the initiator.