Stoichiometrically sensitized decarboxylation occurring in a molecular crystal composed of phenanthridine and 3-indoleacetic acid

Irradiation of a molecular crystal between phenanthridine and 3-indoleacetic acid at –70 °C causes decarboxylation to give 3-methylindole in high yield as the sole product; phenanthridine behaves like a stoichiometric sensitizer in the crystal.