%0 Journal Article
%@ 0024-9297
%A Tehfe, MA
%A Brahmi, MM
%A Fouassier, JP
%A Curran, DP
%A Malacria, M
%A Fensterbank, L
%A Lacôte, E
%A Lalevée, J
%D 2010
%F pittir:17777
%J Macromolecules
%N 5
%P 2261 - 2267
%T N-heterocyclic carbenes-borane complexes: A new class of initiators for radical photopolymerization
%U http://d-scholarship-dev.library.pitt.edu/17777/
%V 43
%X Newly discovered N-heterocyclic carbene-boryl radicals (NHC-BH 2•) derived from readily available N-heterocyclic carbene-boranes are found to be efficient initiators for acrylate photopolymerization. Laser flash photolysis (LFP) experiments were used to generate three carbene-boryl radicals, which were characterized by their transient absorption spectra with the aid of DFT calculations. Rate constants were measured for the generation of the carbene-boryl radicals by hydrogen abstraction with tert--butoxyl radical, a ketophosphonyl radical, and triplet benzophenone. Rate constants were also measured for the reactions of the carbene-boryl radicals with oxygen, three alkenes, two alkyl chlorides, and diphenyliodonium hexafluorophosphate. The observed trends were interpreted with the aid of measured oxidation potentials of the carbene-boranes and calculated ionization potentials of the carbene-boryls. N-Heterocyclic carbeneboranes show excellent potential as both photopolymerization co-initiators and mediators of small molecule radical reactions, and these results will help guide further development in both fields. © 2010 American Chemical Society.