New Photocleavable Structures. Diacylgermane-Based Photoinitiators for Visible Light Curing

Abstract

As bisacylphosphine oxides are highly efficient, cleavable photoinitiators for visible light curing, we were interested in preparing diacylgermane 2. The UV–vis absorption maximum of the n−π* transition was red-shifted up to 50 nm. Photo-DSC results of 2 showed similar reactivity to bisacylphosphine oxides under broadband irradiation experiments. Irradiation with a dental LED lamp gave significantly improved initiation behavior compared to bisacylphosphine oxides and camphorquinone, especially in aqueous acidic primer formulations. Application-oriented tests in dental adhesive or composite formulations showed sufficient storage stability, high photocuring activity, excellent photobleaching behavior, and mechanical properties of the materials.