Shifting from UV to Visible-Light the Activity of Organic Photoinitiators via the Covalent Grafting of Polyoxometalates

Anthracene-,benzophenone-, and anthraquinone-based UVphotoinitiatorshave been, respectively, covalently grafted on the [Mo6O19](2-) polyoxometalate (POM) platform,affording highly colored charge transfer organo-imido Lindqvist complexes.It has been evidenced that photosystems combining N-methyldiethanolamine (MDEA) as the electron donor and these hybridPOMs promote free-radical photopolymerization of acrylate monomerderivatives under irradiation in the visible range, while in similarconditions, no polymerization was observed considering as photoinitiatorsa mixture of the organic and POM precursors. After 800 s, acrylateconversion yields up to 90% under 405 nm LED irradiation and 50% under470 nm LED irradiation were thus obtained considering the POM-imidoanthraquinone(POM-AQ) compound. This shows that such organo-imidoLindqvist species can represent new easy-to-synthesize, efficientvisible-light photoinitiators. Moreover, due to the presence of thePOM, coatings prepared using the POM-AQ/MDEA/soybeanoil epoxidized acrylate photosystem exhibit excellent mechanical properties,with very good flexibility, resistance to brittle fracture, and adherenceto the steel. Finally, POM-AQ was shown to have a remarkablecapacity to generate singlet oxygen species under visible light irradiation,and the antibacterial activity against Staphylococcusaureus under solar light of the related POM-derivedsurface has been demonstrated.