In contrast to the previously investigated hydrated form, anhydrous 2,
4,6-trinitro-1,3,5-benzenetriol, C6H3N3O9, crystallizes in a non-centr
osymmetric space group and shows non-linear optical activity in soluti
on and in the solid state. The nitro groups are rotated out of the pla
ne of the ring, the degree of twist being related to the number of int
ramolecular hydrogen bonds.