A new concept based on the photoredox catalysis is proposed for the design of a photoinitiating system able to efficiently generate, in a single catalytic cycle, both a radical and a cation as initiating species. This is exemplified here by the tris(1,10-phenanthroline)ruthenium(II) (Ru(phen)32+) complex in combination with a diphenyl iodonium salt and a silane. Interesting and promising photopolymerization profiles in free radical photopolymerization (FRP) and free radical promoted cationic photopolymerization (FRPCP) are obtained under air and upon xenon lamp exposure and even soft irradiation conditions (fluorescence bulb, sunlight). An acrylate/epoxide blend is also easily polymerized under air using a fluorescent bulb. The mechanisms are investigated by ESR and Laser Flash Photolysis experiments.
28 November 2011 in Chemistry – A European Journal
Although sulfur dioxide (SO2) has been used as a reagent for organic chemistry for more than one hundred years, being endowed with quite a distinct and varied reactivity profile, which allows the synthesis of a large range of compounds, its notorious toxicity as well as its gaseous state have impeded its frequent utilization by chemists. We summarize recent studies in this emerging area aimed at stimulating its utilization in organic (including organometallic) chemistry thanks to the development of innocuous, bench-stable reliable SO2 donors. Proof-of-concept experiments have also been recently performed in biology with the design of organic SO2 donors having controlled release profiles under physiological conditions, either active against mycobacteria or used for clarifying the role of endogenously produced SO2 in living cells.