Correction: Synthesis and characterization of diacylgermanes: persistent derivatives with superior photoreactivity.

Correction for 'Synthesis and characterization of diacylgermanes: persistent derivatives with superior photoreactivity' by Sabrina D. Püschmann et al., Dalton Trans., 2021, 50, 11965-11974, DOI: 10.1039/D1DT02091A.

Synthesis and characterization of diacylgermanes: persistent derivatives with superior photoreactivity.

Acylgermanes are known as highly efficient photoinitiators. In this contribution, we present the synthesis of new diacylgermanes 4a-evia a multiple silyl abstraction methodology. The method outperforms the state-of-the-art approach (Corey-Seebach reaction) towards diacylgermanes in terms of group tolerance and toxicity of reagents. Moreover, these compounds are decorated with bulky mesityl groups in order to improve their storage stability. The isolated diacylgermanes were characterized by multinuclear NMR-, UV-Vis spectroscopy and X-ray crystallography, as well as photolysis experiments (photobleaching) and photo-DSC measurements (photopolymerization behavior). Upon irradiation with an LED emitting at 385 nm, all compounds except for 4a and 4c bleach efficiently with quantum yields above 0.6. Due to their broad absorption bands, the compounds can be also bleached with blue light (470 nm), where especially 4e bleaches more efficiently than Ivocerin®.

Synthesis of Mixed-Functionalized Tetraacylgermanes.

Tetraacylgermanes are known as highly efficient photoinitiators. Herein, the synthesis of mixed tetraacylgermanes 4 a-c and 6 a-e with a nonsymmetric substitution pattern is presented. Germenolates are crucial intermediates of these new synthetic protocols. The synthesized compounds show increased solubility compared with symmetrically substituted tetraacylgermanes 1 a-d. Moreover, these mixed derivatives reveal broadened n-π* absorption bands, which enhance their photoactivity. Higher absorption of these new compounds at wavelengths above 450 nm causes efficient photobleaching when using an LED emitting at 470 nm. The quantum yields are in the range of 0.15-0.57, depending on the nature of the aroyl substituents. On the basis of these properties, mixed-functionalized tetraacylgermanes serve as ideal photoinitiators in various applications, especially in those requiring high penetration depth. The synthesized compounds were characterized by elemental analysis, IR spectroscopy, NMR and CIDNP spectroscopy, UV/Vis spectroscopy, photolysis experiments, and X-ray crystallography. The CIDNP data suggest that the germyl radicals generated from the new tetraacylgermanes preferentially add to the tail of the monomer butyl acrylate. In the case of 6 a-e only the mesitoyl groups are cleaved off, whereas for 4 a-c both the mesitoyl and the aroyl group are subject to α-cleavage.