Photoinitiating Efficiency of Visible Light Initiators Based on Tetraacyl Derivatives of Germanium and Tin

Abstract

For several years, bisacylgermanium derivatives have been known to be very potent monomolecular initiators for photopolymerization induced by visible light(VL).1In particular, bis-(4-methoxybenzoyl)diethylgermane (Ivocerin®)exhibitsan excellent performance as VL photoinitiator (PI)forpolymerization of dimethacrylate resins in dental materialsand dimethacrylate-based composites,initialized byblue LED curing lights. Recently, a very efficient synthetic method was developed,which allowsthe preparation of tetraacylgermanium derivativesaccording to a facile procedure in excellent yields.2Tetraacylgermanesare characterized bya very strong VL absorptionup to 500nm, very high PI reactivity, and good bleaching behavior. Based on the samesynthetic procedure, we wereable to synthesize the tin analogue tetrakis(2,4,6-trimethylbenzoyl)stannane, which displays a significantbathochromicshiftof theVL absorption bandbeyond 500nm, high reactivityand excellent bleaching behavior. Details on the synthesis, properties and photoinitiating performance of tetraacylgermanium and -tin PIswill be presented.