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

Abstract

In this contribution a convenient synthetic method to obtain tetraacylgermanes Ge[C(O)R] (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.

1,2‐Diketones as photoinitiators of both cationic and free‐radical photopolymerization under UV (392 nm) or Blue (455 nm) LEDs

“…More interestingly, the similar CQ‐based PIS (CQ/iodonium salt (i.e.,[4‐[octyloxy]phenyl]phenyliodonium hexafluoroantimonate)/EDB) was reported for the polymerization of epoxide under blue light conditions for an additive manufacturing approach (i.e., solution mask liquid lithography) . Recently, an increasing number of novel PISs have been emerging and exhibited high efficiency for free‐radical and/or cationic photopolymerization under visible light . These novel PISs are mainly synthesized with designated chemical structures.…”

Multihydroxy‐Anthraquinone Derivatives as Free Radical and Cationic Photoinitiators of Various Photopolymerizations under Green LED

“…Such natural dyes exhibit great potential to act as nontoxic photoinitiators for the fabrication of biocompatible polymeric materials . After the absorption of suitable light, natural dyes are promoted to excited states and can then interact with additives through electron (or energy) transfer reactions to yield active species (e.g., cations or radicals) to initiate photopolymerization reactions . The relevant reactivity between natural dyes and additives is strongly related to their photochemical properties.…”

Acylation of Homoatomic Ge9 Cages and Subsequent Decarbonylation

“…Especially tetraacyl-germanides have ah igh potentiala sh ighly efficient photoinitiatorsf or free-radical polymerization reactions. [21] Herein we present an ew approacht oc arbonyl-derivatized Ge 9 clusterc ompounds. [Ge 9 {Si(SiMe 3 ) 3 } 3 ] À is heterogeneously reactedw ith several Cl(CO)R' compounds in hexane or toluene solutions resulting in the respective neutral carbonyl-functionalized Ge 9 clusterc ompounds [{Si(SiMe 3 ) 3 } 3 Ge 9 (CO)R']w hich are characterized by NMR spectroscopya nd by singlec rystal X-ray diffraction.…”