Reduction of Cu(II) by photochemically generated phosphonyl radicals to generate Cu(I) as catalyst for atom transfer radical polymerization and azide-alkyne cycloaddition click reactions

The photoinduced electron transfer reactions of acylphosphine oxide type photoinitiators with Cu(II)Cl2/N,N,N′,N′′,N′′-pentamethyldiethylenetriamine complex for both atom transfer radical polymerization and copper catalyzed azide-alkyne cycloaddition processes is investigated by laser flash photolysis. The photolytically generated phosphonyl radicals are effective in reducing Cu(II) salts to Cu(I) with rate constants of ∼2 × 109 M−1 s−1.