Zirconocene Dichloride: An Efficient Cleavable Photoinitiator Allowing the in Situ Production of Zr-Based Nanoparticles Under Air.

CpZrCl is presented as both an effective photoinitiator and additive for radical photopolymerization reactions in aerated conditions. This compound is characterized by remarkable properties: (i) an efficiency higher than that of a reference Type I photoinitiator (2,2-dimethoxy-2-phenylacetophenone, DMPA), (ii) an excellent ability, when added to DMPA, to overcome the oxygen inhibition of the polymerization, and (iii) a never reported in situ photoinduced and oxygen-mediated formation of zirconium-based nanoparticles (diameter ranging from 50 to 70 nm). The photochemical properties of CpZrCl are investigated by steady state photolysis and electron spin resonance (ESR) experiments. The high reactivity of this compound is ascribed to a bimolecular homolytic substitution S2 (clearly characterized by molecular orbital calculations) which converts the peroxyls into new polymerization-initiating radicals and oxygenated Zr-based nanoparticles.