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NIR-Sensitized Activated Photoreaction between Cyanines and Oxime Esters: Free-Radical Photopolymerization.

Yulian PangShuheng FanQunying WangDennis OprychAlfred FeilenKnut ReinerDietmar KeilYuriy L SlominskySergey PopovYingquan ZouBernd Strehmel
Published in: Angewandte Chemie (International ed. in English) (2020)
Cyanines comprising either a benzo[e]- or benzo[c,d]indolium core facilitate initiation of radical photopolymerization combined with high power NIR-LED prototypes emitting at 805 nm, 860 nm, or 870 nm, while different oxime esters function as radical coinitiators. Radical photopolymerization followed an initiation mechanism based on the participation of excited states, requiring additional thermal energy to overcome an existing intrinsic activation barrier. Heat released by nonradiative deactivation of the sensitizer favored the system, even under conditions where a thermally activated photoinduced electron transfer controls the reaction protocol. The heat generated internally by the NIR sensitizer promotes generation of the initiating reactive radicals. Sensitizers with a barbiturate group at the meso-position preferred to bleach directly, while sensitizers carrying a cyclopentene moiety unexpectedly initiated the photosensitized mechanism.
Keyphrases
  • electron transfer
  • photodynamic therapy
  • light emitting
  • fluorescent probe
  • fluorescence imaging
  • drug release
  • randomized controlled trial
  • heat stress
  • physical activity
  • quantum dots