Fig. 2: Functionalization of aryl halides via energy transfer or direct excitation mechanism.
From: Copper-mediated etherification via aryl radicals generated from triplet states

a, The catalytic cycle for the functionalization reaction of aryl halides via energy transfer. b, The activation process of aryl halides via energy transfer or direct excitation. c, Etherification reaction of 4-iodobiphenyl via energy transfer. d, Etherification reaction of halogenated anisole via direct excitation. PS, photosensitizer; Nu, nucleophile; CuTC, copper(I) thiophene-2-carboxylate; DBU, 1,8-diazabicyclo[5.4.0]undec-7-ene.