Unprecedented Bifunctional Chemistry of Bis(acyl)phosphane Oxides in Aqueous and Alcoholic Media

Max Schmallegger; Anna Eibel; Jan P Menzel; Anne-Marie Kelterer; Michal Zalibera; Christopher Barner-Kowollik; Hansjörg Grützmacher; Georg Gescheidt

doi:10.1002/chem.201900935

Unprecedented Bifunctional Chemistry of Bis(acyl)phosphane Oxides in Aqueous and Alcoholic Media

Chemistry. 2019 Jul 5;25(38):8982-8986. doi: 10.1002/chem.201900935. Epub 2019 Jun 12.

Authors

Max Schmallegger¹, Anna Eibel¹, Jan P Menzel^{2

3}, Anne-Marie Kelterer¹, Michal Zalibera⁴, Christopher Barner-Kowollik^{2

3}, Hansjörg Grützmacher⁵, Georg Gescheidt¹

Affiliations

¹ Institute of Physical and Theoretical Chemistry, Graz University of Technology, NAWI, Graz, Stremayrgasse 9, 8010, Graz, Austria.
² School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology (QUT), 2 George Street, Brisbane, QLD 4000, Australia.
³ Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstr. 18, Karlsruhe, 76131, Germany.
⁴ Institute of Physical Chemistry and Chemical Physics, Slovak University of Technology in Bratislava, Radlinského 9, Bratislava, 812 37, Slovak Republic.
⁵ Laboratory of Inorganic Chemistry, ETH Zürich, Vladimir-Prelog-Weg 1, Zürich, 8093, Switzerland.

PMID: 31070829
DOI: 10.1002/chem.201900935

Abstract

Tailor-made photoinitiators play an important role for efficient radical polymerisations in aqueous media, especially in hydrogel manufacturing. Bis(acyl)phosphane oxides (BAPOs) are among the most active initiators. Herein, we show that they display a remarkable photochemistry in aqueous and alcoholic media: Photolysis of BAPOs in the presence of water or alcohols provides a new delocalized π-radical, which does not participate in the polymerization. It either converts into a monoacylphosphane oxide acting as a secondary photoactive species or it works as a one-electron reducing agent. Upon the electron-transfer process, it again produces a dormant photoinitiator. We have established the structure and the chemistry of this π radical using steady-state and time-resolved (CIDEP) EPR together with ESI-MS, NMR spectroscopy, and DFT calculations. Our results show that bis(acyl)phosphane oxides act as bifunctional reagents when applied in aqueous and alcoholic media.

Keywords: BAPOs; ESI-MS; NMR spectroscopy; density functional calculations; photochemistry.

Abstract

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