Unraveling the Solid-State Photoreactivity of Carbonylbis(4,1-Phenylene)dicarbonazidate with Laser Flash Photolysis.

Solid-state photoreactions are generally controlled by the rigid and ordered nature of crystals. Herein, the solution and solid-state photoreactivities of carbonylbis(4,1-phenylene)dicarbonazidate ( 1 ) were investigated to elucidate the solid-state reaction mechanism. Irradiation of 1 in methanol yielded primarily the corresponding amine, whereas irradiation in the solid state gave a mixture of photoproducts. Laser flash photolysis in methanol showed the formation of the triplet ketone (T K ) of 1 (τ ∼ 99 ns), which decayed to triplet nitrene 3 1N (τ ∼ 464 ns), as assigned by comparison to its calculated spectrum. Laser flash photolysis of a nanocrystalline suspension and diffuse reflectance laser flash photolysis also revealed the formation of T K of 1 (τ ∼ 106 ns) and 3 1N (τ ∼ 806 ns). Electron spin resonance spectroscopy and phosphorescence measurements further verified the formation of 3 1N and the T K of 1 , respectively. In methanol, 3 1N decays by H atom abstraction. However, in the solid state, 3 1N is sufficiently long lived to thermally populate its singlet configuration ( 1 1N ). Insertion of 1 1N into the phenyl ring to produce oxazolone competes with 3 1N cleavage to form a radical pair. Notably, 1 did not exhibit photodynamic behavior, likely because the photoreaction occurs only on the crystal surfaces.