Acylstannanes: Cleavable and Highly Reactive Photoinitiators for Radical Photopolymerization at Wavelengths above 500 nm with Excellent Photobleaching Behavior

Within this work, a novel acylstannane‐based photoinitiator (PI) is presented. Tetrakis(2,4,6‐trimethylbenzoyl)stannane ( 1 ) displays outstanding properties compared to state‐of‐the‐art acylgermane‐based initiators. Most importantly, the initiator shows absorption up to 550 nm, which allows higher penetration depths, especially in highly filled photopolymers. Besides that, 1 shows extremely high photoinitiating activity towards (meth)acrylic double bonds, as well as very fast photobleaching. Furthermore, unlike many organotin compounds, 1 shows surprisingly low cytotoxicity.