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Acylgermanes: Photoinitiators and Sources for Ge-Centered Radicals. Insights into their Reactivity

Published inJournal of the American Chemical Society, vol. 135, no. 46, p. 17314-17321
Publication date2013
Abstract

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• 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• reacts with butyl acrylate at a rate of 1.2 ± 0.1 × 108 and 3.2 ± 0.2 × 108 M–1 s–1, 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–O 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.

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NESHCHADIN, Dmytro et al. Acylgermanes: Photoinitiators and Sources for Ge-Centered Radicals. Insights into their Reactivity. In: Journal of the American Chemical Society, 2013, vol. 135, n° 46, p. 17314–17321. doi: 10.1021/ja404433u
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ISSN of the journal0002-7863
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