3,4-Di-2-pyridyl-1,2,5-oxadiazole and its perchlorate salt

In 3,4-di-2-pyridyl-1,2,5-oxadiazole (dpo), C12H8N4O, each mol-ecule resides on a twofold axis and inter-acts with eight neighbours via four C - H⋯N and four C - H⋯O inter-actions to generate a three-dimensional hydrogen-bonded architecture. In the perchlorate analogue, 2-[3-(2-pyrid-yl)-1, 2,5-oxadiazol-4-yl]pyridinium perchlorate, C12H9N4O⁺·ClO4 ^- or [Hdpo]ClO4, the [Hdpo]⁺ cation is bisected by a crystallographic mirror plane, and the additional H atom in the cation is shared by the two pyridyl N atoms to form a symmetrical intra-molecular N⋯H⋯N hydrogen bond. The cations and perchlorate anions are linked through C - H⋯O hydrogen bonds and π-π stacking inter-actions to form one-dimensional tubes along the b-axis direction.