Acylgermanes: Photoinitiators and Sources for Ge-Centered Radicals. Insights into their Reactivity
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- 作者：Dmytro Neshchadin ; Arnulf Rosspeintner ; Markus Griesser ; Bernhard Lang ; Sandra Mosquera-Vazquez ; Eric Vauthey ; Vitaly Gorelik ; Robert Liska ; Christian Hametner ; Beate Ganster ; Robert Saf ; Norbert Moszner ; Georg Gescheidt
- 刊名：Journal of the American Chemical Society
- 出版年：2013
- 出版时间：November 20, 2013
- 年：2013
- 卷：135
- 期：46
- 页码：17314-17321
- 全文大小：374K
- 年卷期：v.135,no.46(November 20, 2013)
- ISSN：1520-5126
文摘
Acylgermanes have been shown to act as efficient photoinitiators. In this investigation we show how dibenzoyldiethylgermane 1 reacts upon photoexcitation. Our real-time investigation utilizes femto- and nanosecond transient absorption, time-resolved EPR (50 ns), photo-chemically induced dynamic nuclear polarization, DFT calculations, and GC-MS analysis. The benzoyldiethylgermyl radical G鈥?is formed via the triplet state of parent 1. On the nanosecond time scale this radical can recombine or undergo hydrogen-transfer reactions. Radical G鈥?reacts with butyl acrylate at a rate of 1.2 卤 0.1 脳 108 and 3.2 卤 0.2 脳 108 M鈥? s鈥?, in toluene and acetonitrile, respectively. This is 1 order of magnitude faster than related phosphorus-based radicals. The initial germyl and benzoyl radicals undergo follow-up reactions leading to oligomers comprising Ge鈥揙 bonds. LC-NMR analysis of photocured mixtures containing 1 and the sterically hindered acrylate 3,3-dimethyl-2-methylenebutanoate reveals that the products formed in the course of a polymerization are consistent with the intermediates established at short time scales.