Tetraacylgermanes: Highly Efficient Photoinitiators for Visible-Light-Induced Free-Radical Polymerization

Judith Radebner; Anna Eibel; Mario Leypold; Christian Gorsche; Lukas Schuh; Roland Fischer; Ana Torvisco; Dmytro Neshchadin; Roman Geier; Norbert Moszner; Robert Liska; Georg Gescheidt; Michael Haas; Harald Stueger

doi:10.1002/anie.201611686

Tetraacylgermanes: Highly Efficient Photoinitiators for Visible-Light-Induced Free-Radical Polymerization

Angew Chem Int Ed Engl. 2017 Mar 6;56(11):3103-3107. doi: 10.1002/anie.201611686. Epub 2017 Feb 3.

Affiliations

¹ Institute of Inorganic Chemistry, Technische Universität Graz, Stremayrgasse 9/IV, 8010, Graz, Austria.
² Institute of Physical and Theoretical Chemistry, Technische Universität Graz, Austria.
³ Institute of Applied Synthetic Chemistry and Christian Doppler Laboratory for Photopolymers in Digital and Restorative Dentistry, Technische Universität Wien, Austria.
⁴ Ivoclar Vivadent AG, Schaan, Liechtenstein.

PMID: 28156043
DOI: 10.1002/anie.201611686

Abstract

In this contribution a convenient synthetic method to obtain tetraacylgermanes Ge[C(O)R]₄ (R=mesityl (1 a), phenyl (1 b)), a previously unknown class of highly efficient Ge-based photoinitiators, is described. Tetraacylgermanes are easily accessible via a one-pot synthetic protocol in >85 % yield, as confirmed by NMR spectroscopy, mass spectrometry, and X-ray crystallography. The efficiency of 1 a,b as photoinitiators is demonstrated in photobleaching (UV/Vis), time-resolved EPR (CIDEP), and NMR/CIDNP investigations as well as by photo-DSC studies. Remarkably, the tetraacylgermanes exceed the performance of currently known long-wavelength visible-light photoinitiators for free-radical polymerization.

Keywords: acylgermanes; photochemistry; photoinitiators; radical polymerization; reaction mechanisms.

Publication types

Research Support, Non-U.S. Gov't