Jump to main content
Jump to site search


From mono- to tetraacylgermanes: extending the scope of visible light photoinitiators

Author affiliations

Abstract

We have investigated the inititiaton efficiency of carefully selected germanium-based photointiators for radical polymerization. To establish a systematic relationship between structure and reactivity, we have developed a convenient synthetic protocol for the preparation of a trisacylgermane, closing the gap from mono- to tetraacylgermane photoinitiators. The studied acylgermanes display distinct, wavelength-dependent photobleaching upon irradiation up to 470 nm. In particular, tetraacylgermanes featuring ortho-alkyl substituents reveal red-shifted n–π* bands, in line with excellent photobleaching upon visible light irradiation. Quantum yields of decomposition (determined at 385 nm) have been found to be highest for bisacylgermanes. Germyl radicals produced upon triplet-state α-cleavage of the acylgermanes react remarkably fast with monomers. Addition rate constants to (meth)acrylates range from 0.4–4.5 × 108 M−1 s−1, depending on the substitution pattern. These values are clearly higher than those reported for related phosphorus-centered radicals derived from acylphosphane oxides. We have further established the nature of the products and side-products formed at initial stages of the polymerizations using chemically induced dynamic nuclear polarization (CIDNP) experiments.

Graphical abstract: From mono- to tetraacylgermanes: extending the scope of visible light photoinitiators

Back to tab navigation

Supplementary files

Publication details

The article was received on 15 Sep 2017, accepted on 19 Nov 2017 and first published on 20 Nov 2017


Article type: Paper
DOI: 10.1039/C7PY01590A
Citation: Polym. Chem., 2018, Advance Article
  •   Request permissions

    From mono- to tetraacylgermanes: extending the scope of visible light photoinitiators

    A. Eibel, J. Radebner, M. Haas, D. E. Fast, H. Freißmuth, E. Stadler, P. Faschauner, A. Torvisco, I. Lamparth, N. Moszner, H. Stueger and G. Gescheidt, Polym. Chem., 2018, Advance Article , DOI: 10.1039/C7PY01590A

Search articles by author

Spotlight

Advertisements