SOLID‐STATE PHOTOCHEMISTRY OF INDOLES WITH NAPTHALENE AND PHENANTHRENE

Abstract

Abstract— Solid‐state irradiation of mixed crystals prepared by meltinga 1:3 molar mixture of indole and phenanthrene followed by resolidifying the melt gave an adduct 2a in 13.5% yield. An adduct 2b was obtained by irradiation of the mixed crystals of 3‐methylindole and phenanthrene. Irradiation of the same mixtures of indoles and phenanthrene in solution gave no photoproduct. Irradiation of the mixed crystals of indole and naphthalene gave a similar photoadduct 3a, which was also formed in solution. The 1:1 mixed crystals of indole and phenanthrene and of indole and naphthalene were characterized by various spectroscopic methods. Among them powder X‐ray diffraction spectral analysis and differential scanning calorimetry revealed that the former mixed crystal is a simple mixture of microcrystals of indole and phenanthrene, while the latter forms a molecular compound.