Intermolecular photoreactions of tetracyanobenzene (TCNB) with benzyl cyanide (BzCN), benzyl alcohol (BzOH) and various others were investigated in the solid state (cocrystal) and in solution. The new solid-state photocoupling reaction found for the cocrystal TCNB·BzCN, giving a stilbene derivative followed by the solution isomerization into an isoindole derivative, is a very limited reaction. On the other