crystals of aralkyl carboxylicacids such as 3-indolepropionic acid (a) and 1-naphthylacetic acid (b) combined with acridine (1) or phenanthridine (2) as an electron acceptor. The 1:1 hydrogen bonded crystals were prepared by recrystallization from the solutions. Irradiation of the crystals at −70 °C caused highly selective decarboxylation to give corresponding decarboxylated compounds alone in nearly