1. The Chemistry of Acylgermanes: Triacylgermenolates Represent Valuable Building Blocks for the Synthesis of a Variety of Germanium-Based Photoinitiators
- Author
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Frühwirt, Philipp, Knoechl, Andreas, Pillinger, Michael, Müller, Stefanie M., Wasdin, Perry T., Fischer, Roland C., Radebner, Judith, Torvisco, Ana, Moszner, Norbert, Kelterer, Anne-Marie, Griesser, Thomas, Gescheidt, Georg, and Haas, Michael
- Abstract
The formation of a stable triacylgermenolate 2as a decisive intermediate was achieved by using three pathways. The first two methods involve the reaction of KOtBu or alternatively potassium with tetraacylgermane 1yielding 2via one electron transfer. The mechanism involves the formation of radical anions (shown by EPR). This reaction is highly efficient and selective. The third method is a classical salt metathesis reaction toward 2in nearly quantitative yield. The formation of 2was confirmed by NMR spectroscopy, UV–vis measurements, and X-ray crystallography. Germenolate 2serves as a starting point for a wide variety of organo-germanium compounds. We demonstrate the potential of this intermediate by introducing new types of Ge-based photoinitiators 4b–4f. The UV–vis absorption spectra of 4b–4fshow considerably increased band intensities due to the presence of eight or more chromophores. Moreover, compounds 4d–4fshow absorption tailing up to 525 nm. The performance of these photoinitiators is demonstrated by spectroscopy (time-resolved EPR, laser flash photolysis (LFP), photobleaching (UV–vis)) and photopolymerization experiments (photo-DSC measurements).
- Published
- 2020
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